Home » Posts tagged 'Chemistry' (Page 5)
Tag Archives: Chemistry
Digesting nutrients
This next section comes from BBC KS3 Bitzesize Science, http://www.bbc.co.uk, Organisms, behaviour and health
Enzymes
Special proteins that can break large molecules into small molecules.
Different types of enzymes can break down different nutrients:
-
carbohydrase or amylase ⇒ break down starch into sugar
-
protease ⇒ break down proteins into amino acids
-
lipase ⇒ break down fats into fatty acids and glycerol
Carbohydrates
Saliva in your mouth contains amylase, which is a starch digesting enzyme.
Proteins
Proteins are digested in the stomach and small intestine.
Protease enzymes break down proteins into amino acids.
Digestion of proteins in the stomach is helped by stomach acid, which is strong hydrochloric acid. This also kills harmful micro-organisms that may be in the food.
Fats
Lipase enzymes break down fat into fatty acids and glycerol. Digestion of fat in the small intestine is helped by bile, made in the liver. Bile breaks the fat into small droplets that are easier for the lipase enzymes to work on.
Things that are not digested
Minerals, vitamins and water are already small enough to be absorbed by the body without being broken down
Fiber – these are carbohydrates that our body can’t digest
Breaking proteins and fats down into smaller parts
How does the digestive system break larger molecules down into smaller molecules?
Hydrolysis – adding an H2O molecule can break bonds apart.
Here we see hydrolysis breaking a tiny protein down into two separate amino acids.
(And then, the animation shows how the opposite can occur when needed: How two separate amino acids can be condensed together by removing an OH from one of them, and and H from the other, creating a new H2O molecule left over.)
Similarly, here we see hydrolysis breaking a fat (triglyceride) down into smaller pieces (glycerol and 3 fatty acids.)
(And then, the animation shows how the opposite can occur when needed: How they all can be condensed together by removing an OH from one of them, and and H from the other, creating a new H2O molecule left over.)
How does does starch enter the bloodstream
Absorption and egestion
http://www.bbc.co.uk/bitesize/ks3/science/organisms_behaviour_health/diet_drugs/revision/6/
These are the processes that happen in the digestive system:
ingestion (eating) → digestion (breaking down) → absorption → egestion
Digested food molecules are absorbed in the small intestine. This means that they pass through the wall of the small intestine and into ourbloodstream.
Once in the bloodstream, the digested food molecules are carried around the body to where they are needed.
Only small, soluble substances can pass across the wall of the small intestine.
Large insoluble substances cannot pass through.
The inside wall of the small intestine needs to be thin, with a really big surface area.
This allows absorption to happen quickly and efficiently. If the small intestine had a thick wall and a small surface area, a lot of digested food might pass out of the body before it had a chance to be absorbed.
To get a big surface area, the inside wall of the small intestine is lined with tiny villi (one of them is called a villus).
These stick out and give a big surface area. They also contain blood capillaries to carry away the absorbed food molecules.
Organic molecules in smoke
Burning wood produces a wide array of organic compounds. Each type of wood makes many unique compounds, and the specific compounds formed depend on the amount of oxygen available. Here are a few of them.
Description: nutty roasted hazelnut
—-
nutty nut flesh roasted hazelnut toasted grain
sigmaaldrich.com
Learning Standards
2016 Massachusetts Science and Technology/Engineering Curriculum Framework
HS-LS1-6. Construct an explanation based on evidence that organic molecules are primarily composed of six elements, where carbon, hydrogen, and oxygen atoms may combine with nitrogen, sulfur, and phosphorus to form monomers that can further combine to form large carbon-based macromolecules.
Meaningless words in food science
4 meaningless words: toxin, natural, organic, and GMO
Archived for my students. From The Logic of Science, 8/16/2016
News articles and blog posts are often full of buzzwords that are heavy on emotional impact but light on substance, and for scientific topics such as nutrition, health, medicine, and agriculture, four of the most common buzzwords are “toxins,” “natural,” “organic,” and “GMO.”
These words are used prolifically and are typically stated with clear implications (“toxin” and “GMO” = bad; “natural” and “organic” = good).
The problem is that these words are poorly defined and constantly misused.
They are often used in a way that shifts them into the category of what are referred to as “weasel words,” meaning that their use gives the impression that the author said something concrete and meaningful, when in fact the statement was a null sentence that lacked any real substance.
“Toxins”
Our society seems to be obsessed with “toxins.” The internet is full of purveyors of woo selling everything from expensive fruit cleanses to “earthing” mats, all with the intended purpose of ridding your body of vaguely defined “toxins.”
The problem is simply that there is no such thing as a “toxin.” All matter is made of chemicals (excluding subatomic particles for a minute), and essentially all chemicals are safe at a low enough dose and toxic at a high enough dose (i.e., the dose makes the poison).
So there are toxic doses not toxic chemicals. Even water becomes lethally toxic at a high enough dose (Garigan and Ristedt 1999). So this idea that something is going to rid your body of “toxins” doesn’t make any sense, because the chemicals themselves are not “toxins,” and they only become toxic at a high enough dose.
Take formaldehyde, for example. I often hear people talk about it as a “toxin,” but the reality is that it is an inevitable bi-product of normal biological processes. So not only is it in many fruits and vegetables, but it is actually produced by your body! The chemical itself is not dangerous, but it can become dangerous at a high enough dose.
To be clear, I’m not saying that we shouldn’t pay attention to what we put into our bodies. Of course we should, but we need to evaluate chemicals based on the dose at which they become toxic, not simply based on whether or not they are present.
Addendum (16-Aug-16): “Toxin” does have an actual biological meaning in the context of chemicals that are released by microscopic organisms. These are often toxic to individual cells at incredibly low doses because a cell itself is so small. So when I talked about “toxins” in the post, I was referring to the notion that certain chemicals are automatically dangerous for you as an organism, rather than on a cell by cell basis.
“Natural”
The definition of “natural” seems obviously to be, “found in nature,” but that’s actually a lot more ambiguous and arbitrary than it sounds. First, let’s deal with why this definition is arbitrary, and the best way to explain that is by talking about chemical compounds.
Everything around you is made of chemicals (including you)
In chemistry, a compound is simply the combination of two or more different elements. So most of the things that are around you are in fact chemical compounds (there are several thousand compounds that make your body, for example).
Now, many people like to distinguish between “natural” and “synthetic” chemicals, where “natural” chemicals can be found in nature, while “synthetic” ones were produced in a lab, but that distinction is arbitrary. A chemical is a chemical, and on a molecular level, there is nothing that separates natural and synthetic chemicals.
All chemical compounds are made by stringing different elements together, and there is no inherent difference between nature stinging elements together and scientists stringing elements together. We can make acids in the lab and you can find acids in nature, we can make chemicals that are poisonous at anything but a low dose in the lab, and you can find chemicals that are poisonous at anything but a low dose in nature, etc.
The fact that something was synthesized in a lab doesn’t make it any more dangerous or any safer than a chemical that was found in nature.
Consider, for example, acetylsalicylic acid and salicylic acid. One of those is natural and the other is synthetic.
Can you tell which? No, and neither could a chemist. If you showed those two molecules to a chemist who had no prior information about those chemicals, there is no way they she could tell you which was natural and which was synthetic, because that distinction is arbitrary.
In all likelihood though, she would know which is which because these are two very well-known compounds. Salicylic acid is the compound in willow bark that gives it medicinal value, and acetylsalicylic acid is the synthetic version of it that we all know as aspirin.
Further, we switched to the synthetic version largely because straight salicylic acid has a lot of unpleasant side effects like gastrointestinal problems (Hedner and Everts 1997).
To be clear, aspirin has side effects as well (as do all chemicals), but they tend to be less severe, and the point is, once again, that simply being natural doesn’t automatically make something better. Indeed, asserting that something is better because it is natural is a logical fallacy known as an appeal to nature.
Moving beyond the arbitrariness of what is natural, the typical definition of “found in nature” doesn’t apply to some things that most people would intuitively think of as natural.
Take apples, for example. They’re natural, right? Not so much. The fruit that we know as an apple does not grow in nature. As I will talk about more later, essentially all of our crops have been modified by thousands of years of careful breeding, so, technically speaking, they aren’t natural.
The situation is even more problematic when we talk about actions rather than objects. People often say things like, “we should do X, because X is natural,” but what on earth does that mean?
Generally, I hear people say that it means what our ancestors did, but that raises the obvious question of how far back do we have to go for something to be natural? Are we talking about 200 years ago? 1,000 years ago? 10,000 years ago? etc. This definition is horribly ambiguous.
To get around this problem, some people say that natural actions are those that are found in the animal kingdom, but that is also an extremely problematic definition for a number of reasons.
First, how widespread does it need to be in the animal kingdom? Is it simply required to find one animal that does it? Further, there are lots of human actions that most people think of as natural, even though other animals don’t do them. For example, we cook our food. Does that making cooking unnatural?
Finally, this definition is fundamentally flawed because we are just highly evolved animals, so doesn’t that make everything that we do natural? Actually think about this for a second. I think that we can all agree that structures like bird nests and beaver dams are natural, but those are not structures that just form spontaneously in nature. Rather, they are carefully and deliberately constructed by an animal who uses materials to make them.
Nevertheless, if I make a wooden table, most people would agree that the table is unnatural, but how on earth is that any different from a beaver dam? The beaver is an animal that took materials found in nature and combined them to make a new structure, and I am an animal that took materials found in nature and combined them to make a new structure. What’s the difference?
Further, we can logically extend this to all human structures. When you get right down to it, all of the parts of a skyscraper came from nature, and there is no logical reason to say that a beaver combining sticks and mud to make a dam is natural but me combing two metals to make steel is unnatural. Again, the definition of natural is completely arbitrary and functionally meaningless.
“GMO”
GMO stands for “Genetically Modified Organism,” and you may think that this has a very clear and precise definition…but it really doesn’t. Before reading the rest of this, try to come up with a definition of it yourself, then see how that definition holds up.
The most general line of thought would be that a GMO is exactly what is says: “an organism whose genes have been altered,” but that definition is much too broad.
Every living organism has a genetic code that has been altered from its ancestral state by millions of years of evolution. If you really think about it, we are all just heavily modified cyanobacteria (cyanobacteria [or some similar organisms] where most likely the first living cells).
Now you may think that I am stretching things a bit here, and perhaps I am, but “nature” does all sorts of crazy things like hybridizing species (as plants do frequently) and even stealing the DNA from one organism and inserting it into the genetic code of another.
For example, at some point in the evolution of the sweet potato, it managed to modify its genetic code by inserting bacterial genes into its DNA. In other words, it is a transgenic species whose genetic code is a combination of the genes of several species. Shouldn’t that make it a GMO?
Further, this is not limited to sweet potatoes, because bacteria themselves are well known for their ability to incorporate the DNA of other species into their own genomes. So nature is constantly doing the types of things that most people would associate with GMOs, and foods like sweet potatoes really are transgenic species.
Nevertheless, you can try to qualify the term GMO by saying that GMOs are, “organisms that have been genetically modified by humans,” but that definition is also fraught with problems. Beyond the fact that it is totally arbitrary (see the “natural” section), it also would encompass all modern agriculture.
Those delicious fruits that you know as watermelons don’t exist in nature (at least not in their current form). Similarly, natural bananas are small and full of giant seeds, and wild corn does not produce those nice juicy husks that you slather in butter and salt. Both our livestock and crops have been genetically modified through years selective breeding, and they contain genetic codes that aren’t found in nature.
[All the “natural” corn we eat has been extensively genetically modified by thousands of years of artificial selection.]
At this point, people often try to add something about moving genes between species, but that just creates more problems. First, nature does that as well…
Second, that would also include lots of “non-GMO” crops such as pluots, plumcots, tangelos, etc. all of which are hybrids that used selective breeding to combine the DNA of two different species.
Given the problems with that definition, you might try defining a GMO as an organism that is “modified by humans via a method other than selective breeding,” but that definition includes mutation breeding, which is typically not considered to be a GMO.
This method uses chemicals or UV radiation to randomly mutate organisms’ DNA in order to produce new and useful traits (i.e., it makes genetic modifications via inducing mutations). However, this method typically does not receive the label “GMO,” and in some cases, even farms that label themselves as “organic” can us crops that were produced by this method.
This leaves us with the outrageous definition that a GMO is, “an organism whose DNA was modified by humans via a method other than selective breeding or mutation breeding,” but at that point we have tacked so many arbitrary qualifiers onto the term, that the term itself is essentially meaningless.
“Organic”
Finally, let’s talk about the term “organic.” This is perhaps the greatest marketing term ever coined, and the problem with it is not that a definition doesn’t exist, but rather that the definition is arbitrary and most people don’t use it correctly (to be clear, I am talking specifically about organic farming practices, not organic chemistry.)
Here is a question for you, true or false, organic farming doesn’t use pesticides?
Organic farmers absolutely use pesticides, and many of those pesticides are toxic at comparable doses to the pesticides used in traditional farming.
Indeed, organic pesticides have can harm wild species, pollute waterways, and do all of the other harmful things that traditional pesticides can do (Bahlai et al. 2010). In fact, one of the most common organic pesticides is “Bacillus thuringiensis (Bt) toxin,” which is the exact same chemical that GMO corn produces (i.e., Bt maize).
So one the one hand, organic farmers use Bt liberally, and on the other hand, they demonize corn that produces Bt. Are you starting to see why this is arbitrary ?
So if organic crops use potentially dangerous pesticides just as much as traditional crops, then what exactly does it take for a crop to be considered organic? Generally speaking, they have to be grown without synthetic pesticides (“natural” are fine) and without the use of GMOs (some countries place additional requirements like no petroleum-based fertilizers). …
Yet distinction between “natural” and “synthetic” chemicals is arbitrary and all chemicals are safe at a low dose and toxic at a high enough dose… and the term GMO is really arbitrary. So, since the definition of organic relies on those other terms, the “organic” label is itself arbitrary.
To put this another way, organic crops are not automatically healthier or more nutritious than traditional crops. Indeed, reviews of the literature have been unable to find consistent and compelling evidence that organic food is healthier (Smith-Spangler et al. 2012; Galgano et al. 2015).
Now, at this point, you may be thinking that organic crops aren’t healthier, but surely they are better for the environment. However, that is also a misnomer. Some practices that are typically associated with organic farming are better for the environment, but those practices are sometimes included in non-organic farming as well, and organic farming has serious drawbacks, such as the fact that it often uses far more land and resources than traditional farming (Tuomisto et al. 2012).
As a result, you can’t make a blanket statement like, “organic farming is better for the environment” because in many cases it isn’t.
The point is that simply saying that something is “organic” doesn’t actually tell you anything useful about how healthy it is or whether or not it was grown in a sustainable way.
Also see https://thelogicofscience.com/2015/11/16/the-real-frankenfoods/
Citations
Bahlai et al. 2010. Choosing organic pesticides over synthetic pesticides may not effectively mitigate environmental risk in soybeans. PLoS ONE 5:e11250.
Doucleff. 2015. Natural GMO? Sweet potato genetically modified 8,000 years ago. NPR: Food and Culture
Garigan and Ristedt 1999. Death from hyponatremia as a result of acute water intoxication in an Army basic trainee. Military Medicine 164:234–238.
Galgano et al. 2015. Conventional and organic foods: A comparison focused on animal products. Cogent Food and Agriculture 2: 1142818.
Hedner and Everts 1997. The early clinical history of salicylates in rheumatology and pain. Clinical Rheumatology 17:17–25.
Ruishalme. 2015. Natural assumptions. Thoughtscapism.com. Accessed 15-Aug-16
Smith-Spangler et al. 2012. Are organic foods safer or healthier than conventional alternatives? A systematic review. Annals of Internal Medicine 157:348–366.
Tuomisto et al. 2012. Does organic farming reduce environmental impacts? A meta-analysis. Journal of Environmental Management, 112:309–320.
Wilcox. 2011. Mythbusting 101: Organic farming > conventional agriculture. Scientific American.
Related articles
Meaningless words in food science
Nutrients
Organic food and farming
Meaningless words in food science
What we need to know about healthy diets
Healthy meal generator
This website is educational. Materials within it are being used in accord with the Fair Use doctrine, as defined by United States law.
§107. Limitations on Exclusive Rights: Fair Use. Notwithstanding the provisions of section 106, the fair use of a copyrighted work, including such use by reproduction in copies or phone records or by any other means specified by that section, for purposes such as criticism, comment, news reporting, teaching (including multiple copies for classroom use), scholarship, or research, is not an infringement of copyright. In determining whether the use made of a work in any particular case is a fair use, the factors to be considered shall include: the purpose and character of the use, including whether such use is of a commercial nature or is for nonprofit educational purposes; the nature of the copyrighted work; the amount and substantiality of the portion used in relation to the copyrighted work as a whole; and the effect of the use upon the potential market for or value of the copyrighted work.
(added pub. l 94-553, Title I, 101, Oct 19, 1976, 90 Stat 2546)
MCAS Biochemistry questions
Sample Questions
Feb 2016 Bio MCAS
ATP molecules in cells undergo a process called hydrolysis. The equation below represents this process.
ATP + H2O → ADP + Pi [ + energy ]
( Pi = inorganic phosphate)
What always happens within cells as a result of ATP hydrolysis?
A. Water is produced.
B. Chemical energy is released.
C. Phosphorus atoms are used up.
D. Carbohydrate building blocks are formed.
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
An English doctor is given credit for developing the modern terrarium in the 1800s. The doctor kept some plants in a sealed glass jar containing soil and air. The plants survived in the sealed jar for four years. What two processes allowed the plants to cycle nutrients and survive in the sealed jar?
A. meiosis and fertilization
B. mutualism and commensalism
C. photosynthesis and cellular respiration
D. asexual reproduction and sexual reproduction
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Scientists use satellite data to produce images such as the one below, showing the density of plants across Earth’s different land areas. Scientists study these images to determine how plant density changes during a year. They can then use this information to help predict carbon dioxide concentrations in the atmosphere in different locations and at different times of the year.
Which of the following best explains why scientists can predict carbon dioxide concentrations from plant density data?
A. Plants add carbon dioxide to theatmosphere during germination.
B. Plants add carbon dioxide to the atmosphere during transpiration.
C. Plants remove carbon dioxide from the atmosphere during photosynthesis.
D. Plants remove carbon dioxide from the atmosphere during cellular respiration.
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Which of the following are mainly cycled through the processes of photosynthesis and cellular respiration?
A. carbon and sulfur
B. carbon and oxygen
C. nitrogen and sulfur
D. nitrogen and oxygen
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Some diseases decrease the activity of certain enzymes in the mitochondria of cells. Which of the following is the most direct result of this decreased enzyme activity?
A. The cells are not able to divide by mitosis.
B. The cells are not able to move water by diffusion.
C. The cells produce less ATP by cellular respiration.
D. The cells produce fewer sugars by photosynthesis.
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Feb 2017 MCAS.
Some bacteria produce cellulase, a substance that speeds up the breakdown
of cellulose in plant cell walls. Cellulase is an example of which of the following?
A. a carbohydrate B. an enzyme C. a hormone D. an organelle
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Feb 2017 MCAS. Protein pumps actively transport ions across a cell’s plasma membrane. What molecule directly supplies the energy required for this transport?
A. ATP B. cholesterol C. oxygen D. tRNA
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Spring 2017
Collagen is found in connective tissue throughout the human body. Collagen is made of three amino acid chains that are twisted around one another. Which of the following best explains why collagen is classified as a protein?
A. It is found in a tissue.
B. It is made up of amino acids.
C. It is made up of twisted chains.
D. It is found throughout the human body
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Spring 2017
Which of the following is a characteristic that distinguishes
viruses from B. thetaiotaomicron and S. epidermidis?
A. Viruses lack mitochondria.
B. Viruses lack genetic material.
C. Viruses are unable to accumulate mutations.
D. Viruses are unable to reproduce outside of host cells.
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Which of the following describes one way B. thetaiotaomicron helps in digestion?
A. It breaks down lipids into fatty acids.
B. It breaks down proteins into amino acids.
C. It breaks down polysaccharides into simpler sugars.
D. It breaks down nucleic acids into nitrogenous bases.
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
A scientist is trying to determine how closely related two species of plants are. Which of the following would be most useful for the scientist to compare?
A. the root depths of the plants
B. the leaf structures of the plants
C. the genetic sequences of the plants
D. the nutrient requirements of the plants
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Spring 2017 . Which of the following best describes how enzymes affect chemical reactions?
A. They speed up the rate of reactions.
B. They change the reactants into ions.
C. They dissolve the products of
reactions.
D. They take the place of one of the
reactants.
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
The diagram below shows a chloroplast and some of the components of the
reactions that occur in chloroplasts.
Which of the following is a product of the reactions that take place in a chloroplast?
A. hydrogen gas
B. nitrate
C. oxygen gas
D. protein
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
In which of the following ways does the plasma membrane [lipid bilayer] regulate the entry of molecules into a cell?
A. The membrane allows only certain molecules to move into the cell.
B. The membrane destroys most molecules so that they do not enter the cell.
C. The membrane changes only certain molecules into ions before they move into the cell.
D. The membrane allows most molecules to transfer energy to the cell without entering the cell.
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Spring 2017
In a cell, a phosphate group is added to ADP to form ATP. Which of the
following best describes the importance of the formation of ATP?
A. It connects amino acids.
B. It provides energy for the cell.
C. It creates new polysaccharides.
D. It catalyzes chemical reactions.
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
The energy that primary consumers use for metabolism and growth comes
directly from which of the following sources?
A. organic compounds synthesized by producers
B. organic compounds released by decomposers
C. organic compounds stored in carnivore tissues
D. organic compounds absorbed from the environment
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Which of the following statements describes a difference between
photosynthesis and cellular respiration in plants?
A. Photosynthesis occurs only during the day, whereas cellular respiration occurs only at night.
B. Photosynthesis involves only one reaction, whereas cellular respiration involves many steps.
C. Photosynthesis occurs only in cells containing chlorophyll, but cellular respiration occurs in all cells.
D. Photosynthesis converts light energy into chemical energy, but cellular respiration converts light energy into heat energy
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
During the processes of respiration and photosynthesis in plant cells, what are the three primary elements that cycle between the mitochondria and chloroplasts?
A. carbon, iron, and sulfur
B. hydrogen, carbon, and oxygen
C. carbon, nitrogen, and phosphorus
D. hydrogen, oxygen, and potassium
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Which of the following happens when a phosphate-phosphate bond in an ATP molecule is broken?
A. Energy is released in a cell.
B. Light energy is absorbed in a plant cell.
C. Water is transported into an animal cell.
D. Lysosome contents are released in a cell.
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Some cell types contain thousands of mitochondria. These cells are likely
to use large amounts of which of the following?
A. ATP
B. carbon dioxide
C. DNA
D. nitrogen
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
The table below provides information about the composition and function of four
important molecules in living organisms.
Which of the molecules in this table is a carbohydrate?
A. 1
B. 2
C. 3
D. 4
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Question 23 is an open-response question.
• BE SURE TO ANSWER AND LABEL ALL PARTS OF THE QUESTION.
• Show all your work (diagrams, tables, or computations) in your Student Answer Booklet. If you do the work in your head, explain in writing how you did the work. Write your answer to question 23 in the space provided in your Student Answer Booklet.
●23 Catalase is an enzyme that protects cells from damage by helping convert the toxin hydrogen peroxide (H O2 2) into water (H O2 ) and oxygen (O2). A student is investigating how different pH values and different temperatures affect catalase activity. The table below shows the student’s data.
a. Identify the test tube that most likely has physical conditions similar to the conditions in human cells. Explain your answer.
b. Describe how catalase activity changes as pH decreases. Use data from the table to support your answer.
c. Describe how catalase activity changes as temperature increases. Use data from the table to support your answer.
d. Explain why temperature affects catalase activity in the way you described in part (c)
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
The body structure of a reef-building coral consists of a hard skeleton covering soft tissue. Which of the following elements is most common in the coral’s soft tissue?
A. carbon
B. chlorine
C. sodium
D. zinc
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
The growth of most plants is limited by the amount of nitrogen available. Which of the following effects does low nitrogen availability most likely have on the carbon cycle?
A. More carbon dioxide is taken up by plants.
B. Carbon dioxide is trapped in the soil around plants.
C. Less carbon dioxide is removed from the atmosphere.
D. Carbon dioxide is converted to carbonates by bacteria.
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Which process do elk and other Yellowstone animals use to convert energy in their food into ATP?
A. cellular respiration
B. filtration
C. osmosis
D. photosynthesis
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Which of the following will most likely change when an enzyme is added to a reaction?
A. the pH of the reaction
B. the rate of the reaction
C. the products of the reaction
D. the temperature of the reaction
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Cellulose is a compound found in plants. It is made of a long
chain of molecules with ringed structures. The molecules contain
mostly carbon, hydrogen, and oxygen atoms in a ratio of approximately
1 carbon : 2 hydrogen : 1 oxygen.
To which category of biological molecules does cellulose belong?
A. carbohydrates
B. nucleic acids
C. phospholipids
D. proteins
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Some types of bacteria are able to perform photosynthesis. These bacteria must therefore contain which of the following in their membranes?
A. chlorophyll
B. glucose
C. mitochondria
D. ribosomes
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
What directly supplies the energy needed to actively transport sodium ions across the plasma membrane of a cell?
A. ATP B. DNA C. enzyme D. lipids
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Photosynthesis is most likely to occur in which of the following cells?
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Many farm animals eat hay, which is made by cutting and drying plants such as ryegrass and timothy grass. Scientists analyzed the composition of hay after it was cut and again after it was dried. The amounts of which common biological elements would have decreased the most as the hay dried?
A. sulfur and calcium
B. phosphorus and zinc
C. oxygen and hydrogen
D. nitrogen and chlorine
Fat How it gets made and broken down
How does fat get made?
We eat to (a) have building materials for our cells, and (b) to get energy for chemical reactions in our cells.
Excess protein or carbohydrates get broken down, and rebuilt as fat molecules, usually triglycerides.
What happens to fat when it is broken down?
Eventually, broken down fat turns into CO2 and H2O. The H2O stays in your body as regular water, and excess water is removed by sweating and urination. The CO2 is removed as you exhale.
When you lose weight, where does it go? Turns out, most of it is exhaled.
Myth: Fat gets burned, and turned into “energy” or heat.
Reality: Fat is made of atoms. Those atoms get broken apart and rearranged into other molecules.
To lose weight, we must break triglycerides into smaller molecules. We need oxygen to do this. Part of this process is oxidation.
Doesn’t happen all in one step.
Some fats get converted to Aceryl-CoA and glycolysis intermediates, but even these will eventually break down int into CO2 and H2O.
When a triglyceride is oxidized the process consumes many molecules of oxygen while producing carbon dioxide (CO2) and water (H2O) as waste products.
So, for example, to burn 10 kilograms (22 lbs.) of fat, a person needs to inhale 29 kg (64 lbs.) of oxygen….
burning that fat will produce 28 kg (62 lbs.) of carbon dioxide and 11 kg (24 lbs.) of water.
“None of this biochemistry is new, but for unknown reasons it seems nobody has thought of performing these calculations before,” study authors Ruben Meerman and Andrew Brown of the University of New South Wales in Australia, said…. during weight loss, 84 percent of the fat that is lost turns into CO2 and leaves the body through the lungs, whereas the remaining 16 percent becomes water, according to the study.
“These results show that the lungs are the primary excretory organ for weight loss. The water formed may be excreted in the urine, feces, sweat, breath, tears or other bodily fluids, and is readily replenished,” the researchers said.
The calculations also show the frightening power of, for example, a small muffin over an hour of exercise: At rest, a person who weighs 154 pounds (70 kg) exhales just 8.9 mg of carbon with each breath. Even after an entire day, if this person only sits, sleeps, and does light activities, he or she exhales about 200 grams of carbon, the researchers calculated. A 100 g muffin can cover 20 percent of what was lost.
On the other hand, replacing one hour of rest with exercise such as jogging, removes an additional 40 g of carbon from the body, the researchers said. Even if one traces the fates of all the atoms in the body, the secret to weight loss remains the same: In order to lose weight, one needs to either eat less carbon or exercise more to remove extra carbon from the body.
– Exhaled Pounds: How Fat Leaves the Body, Bahar Gholipour, Live Science, 12/14
Reference: When somebody loses weight, where does the fat go?
BMJ 2014; 349 doi: https://doi.org/10.1136/bmj.g7257 (Published 16 December 2014)
Abstract: When somebody loses weight, where does the fat go?
Considering the soaring overweight and obesity rates and strong interest in this topic, there is surprising ignorance and confusion about the metabolic process of weight loss among the general public and health professionals alike. We encountered widespread misconceptions about how humans lose weight among general practitioners, dietitians, and personal trainers (fig 1⇓). Most people believed that fat is converted to energy or heat, which violates the law of conservation of mass. We suspect this misconception is caused by the “energy in/energy out” mantra and the focus on energy production in university biochemistry courses. Other misconceptions were that the metabolites of fat are excreted in the faeces or converted to muscle. We present a novel calculation to show how we “lose weight.”
Learning standards
Massachusetts Curriculum Frameworks: Biology
8.MS-PS1-1. Develop a model to describe that (a) atoms combine in a multitude of ways to produce pure substances which make up all of the living and nonliving things that we encounter, (b) atoms form molecules and compounds that range in size from two to thousands of atoms, and (c) mixtures are composed of different proportions of pure
substances.
HS-LS1-6. Construct an explanation based on evidence that organic molecules are primarily composed of six elements, where carbon, hydrogen, and oxygen atoms may combine with nitrogen, sulfur, and phosphorus to form monomers that can further combine to form large carbon-based macromolecules.
Clarification Statements:
• Monomers include amino acids, mono- and disaccharides, nucleotides, and fatty acids.
• Organic macromolecules include proteins, carbohydrates (polysaccharides), nucleic acids, and lipids.
Disciplinary Core Idea Progression Matrix: PS1.A Structure of matter
That matter is composed of atoms and molecules can be used to explain the properties of substances, diversity of materials, how mixtures will interact, states of matter, phase changes, and conservation of matter.
Peptide bonds – How we make proteins
2 amino acids can join to form a peptide.
A very long peptide is known as a protein.
When they join one of the amino acid’s loses an H atom, while the other loses an OH moiety (part of a molecule) They join together to form H2O (water.) This is a condensation reaction.
Doc Kaiser’s Microbiology Home Page (Gary E. Kaiser)
Here is another animation of the same process
The CONH link created is called a peptide bond (red)
Water (blue) is removed.
This process can be continued repeatedly to form longer peptides (eventually, when they are over 50 amino acids long, we call them proteins.)
BioTopics.co.uk by Richard Steane
The monomer here is an amino acid.
The polymer here is a peptide or protein.
These are 20 different types of common amino acids.
Amino acids are bonded together to make peptides, or proteins.
A peptide is just a small protein, less than 50 amino acids (aa) long.
Proteins are much larger, 100 aa, 500 aa, even 1,000 aa.
A chain of amino acids folds up into a shape.
Every protein has its own shape.
Scientists argue that addiction is not a disease
Addiction is not a disease
A neuroscientist argues that it’s time to change our minds on the roots of substance abuse, Laura Miller, for Salon. 6/27/15
A psychologist and former addict insists that the illness model for addiction is wrong, and dangerously so.
The mystery of addiction — what it is, what causes it and how to end it — threads through most of our lives. Experts estimate that one in 10 Americans is dependent on alcohol and other drugs, and if we concede that behaviors like gambling, overeating and playing video games can be addictive in similar ways, it’s likely that everyone has a relative or friend who’s hooked on some form of fun to a destructive degree. But what exactly is wrong with them? For several decades now, it’s been a commonplace to say that addicts have a disease. However, the very same scientists who once seemed to back up that claim have begun tearing it down.
Once, addictions were viewed as failures of character and morals, and society responded to drunks and junkies with shaming, scolding and calls for more “will power.” This proved spectacularly ineffective, although, truth be told, most addicts do quit without any form of treatment. Nevertheless, many do not, and in the mid-20th century, the recovery movement, centered around the 12-Step method developed by the founders of Alcoholics Anonymous, became a godsend for those unable to quit drinking or drugging on their own. The approach spread to so-called “behavioral addictions,” like gambling or sex, activities that don’t even involve the ingestion of any kind of mind-altering substance.
Much of the potency of AA comes from its acknowledgement that willpower isn’t enough to beat this devil and that blame, rather than whipping the blamed person into shape, is counterproductive. The first Step requires admitting one’s helplessness in the face of addiction….
…. Another factor promoting the disease model is that it has ushered addiction under the aegis of the healthcare industry, whether in the form of an illness whose treatment can be charged to an insurance company or as the focus of profit-making rehab centers.
….The recovery movement and rehab industry (two separate things, although the latter often employs the techniques of the former) have always had their critics, but lately some of the most vocal have been the neuroscientists whose findings once lent them credibility.
One of those neuroscientists is Marc Lewis, a psychologist and former addict himself, also the author of a new book “The Biology of Desire: Why Addiction is Not a Disease.”
Lewis’s argument is actually fairly simple: The disease theory, and the science sometimes used to support it, fail to take into account the plasticity of the human brain. Of course, “the brain changes with addiction,” he writes. “But the way it changes has to do with learning and development — not disease.” All significant and repeated experiences change the brain; adaptability and habit are the brain’s secret weapons. The changes wrought by addiction are not, however, permanent, and while they are dangerous, they’re not abnormal.
Through a combination of a difficult emotional history, bad luck and the ordinary operations of the brain itself, an addict is someone whose brain has been transformed, but also someone who can be pushed further along the road toward healthy development. (Lewis doesn’t like the term “recovery” because it implies a return to the addict’s state before the addiction took hold.)
“The Biology of Desire” is grouped around several case studies, each one illustrating a unique path to dependency. A striving Australian entrepreneur becomes caught up in the “clarity, power and potential” he feels after smoking meth, along with his ability to work long hours while on the drug. A social worker who behaves selflessly in her job and marriage constructs a defiant, selfish, secret life around stealing and swallowing prescription opiates. A shy Irishman who started drinking as a way to relax in social situations slowly comes to see social situations as an occasion to drink and then drinking as a reason to hole up in his apartment for days on end.
Each of these people, Lewis argues, had a particular “emotional wound” the substance helped them handle, but once they started using it, the habit itself eventually became self-perpetuating and in most cases ultimately served to deepen the wound.
Each case study focuses on a different part of the brain involved in addiction and illustrates how the function of each part — desire, emotion, impulse, automatic behavior — becomes shackled to a single goal: consuming the addictive substance. The brain is built to learn and change, Lewis points out, but it’s also built to form pathways for repetitive behavior, everything from brushing your teeth to stomping on the brake pedal, so that you don’t have to think about everything you do consciously. The brain is self-organizing. Those are all good properties, but addiction shanghais them for a bad cause.
As Lewis sees it, addiction really is habit; we just don’t appreciate how deeply habit can be engraved on the brain itself. “Repeated (motivating) experience” — i.e., the sensation of having one’s worries wafted away by the bliss of heroin — “produce brain changes that define future experiences… So getting drunk a lot will sculpt the synapses that determine future drinking patterns.”
More and more experiences and activities get looped into the addiction experience and trigger cravings and expectations like the bells that made Pavlov’s dogs salivate, from the walk home past a favorite bar to the rituals of shooting up. The world becomes a host of signs all pointing you in the same direction and activating powerful unconscious urges to follow them. At a certain point, the addictive behavior becomes compulsive, seemingly as irresistibly automatic as a reflex. You may not even want the drug anymore, but you’ve forgotten how to do anything else besides seek it out and take it.
Yet all of the addicts Lewis interviewed for “The Biology of Desire” are sober now, some through tried-and-true 12-Step programs, others through self-designed regimens, like the heroin addict who taught herself how to meditate in prison. Perhaps it’s no surprise that a psychologist would argue for some form of talk therapy addressing the underlying emotional motivations for turning to drugs. But Lewis is far from the only expert to voice this opinion, or to recommend cognitive behavioral therapy as a way to reshape the brain and redirect its systems into less self-destructive patterns.
Without a doubt, AA and similar programs have helped a lot of people. But they’ve also failed others. One size does not fit all, and there’s a growing body of evidence that empowering addicts, rather than insisting that they embrace their powerlessness and the impossibility of ever fully shedding their addiction, can be a road to health as well.
If addiction is a form of learning gone tragically wrong, it is also possible that it can be unlearned, that the brain’s native changeability can be set back on track. “Addicts aren’t diseased,” Lewis writes, “and they don’t need medical intervention in order to change their lives. What they need is sensitive, intelligent social scaffolding to hold the pieces of their imagined future in place — while they reach toward it.”
Further reading
The Irrationality of Alcoholics Anonymous
Its faith-based 12-step program dominates treatment in the United States. But researchers have debunked central tenets of AA doctrine and found dozens of other treatments more effective. By Gabrielle Glaser, The Atlantic 4/2015 The Irrationality of Alcoholics Anonymous, The Atlantic
The Surprising Failures of 12 Steps
How a pseudoscientific, religious organization birthed the most trusted method of addiction treatment. By Jake Flanagan 3/25/2014
https://www.theatlantic.com/health/archive/2014/03/the-surprising-failures-of-12-steps/284616/
Why the Disease Definition of Addiction Does Far More Harm Than Good.
Among other problems, it has obstructed other channels of investigation, including the social, psychological and societal roots of addiction. By Marc Lewis on February 9, 2018
…Viewing addiction as pathology has other, more direct detriments. If you feel that your addiction results from an underlying pathology, as implied by the brain disease model, and if that pathology is chronic, as highlighted by both NIDA and the 12-step movement, then you are less likely to believe that you will ever be free of it or that recovery can result from your own efforts. This characterization of addiction flies in the face of research indicating that a great majority of those addicted to any substance or behavior do in fact recover, and most of those who recover do so without professional care.
Why the Disease Definition of Addiction Does Far More Harm Than Good. Scientific American.
Addiction and the Brain: Development, Not Disease
By Mark Lewis, Neuroethics, April 2017, Volume 10, Issue 1, pp 7–18
I review the brain disease model of addiction promoted by medical, scientific, and clinical authorities in the US and elsewhere. I then show that the disease model is flawed because brain changes in addiction are similar to those generally observed when recurrent, highly motivated goal seeking results in the development of deep habits, Pavlovian learning, and prefrontal disengagement. This analysis relies on concepts of self-organization, neuroplasticity, personality development, and delay discounting. It also highlights neural and behavioral parallels between substance addictions, behavioral addictions, normative compulsive behaviors, and falling in love. I note that the short duration of addictive rewards leads to negative emotions that accelerate the learning cycle, but cortical reconfiguration in recovery should also inform our understanding of addiction. I end by showing that the ethos of the disease model makes it difficult to reconcile with a developmental-learning orientation.
Addiction and the Brain: Development, Not Disease. Neuroethics (journal)
The chronic disease concept of addiction: Helpful or harmful?
Thomas K. Wiens & Lawrence J. Walker. Addiction Research & Theory, Volume 23, 2015 – Issue 4
This study provides empirical support to the notion that framing addiction within a biological conceptualisation, as opposed to a psychological and social framework, weakens perceptions of agency in relation to drinking. Likewise, no evidence was found to support the common assertion that the disease model reduces feelings of stigma and shame.
The chronic disease concept of addiction: Helpful or harmful?
Probability and predictors of remission from lifetime nicotine, alcohol, cannabis, or cocaine dependence
Results from the National Epidemiologic Survey on Alcohol and Related Conditions
By Catalina Lopez-Quintero, M.D., M.P.H., Deborah S. Hasin, Ph.D., […], and Carlos Blanco, M.D., Ph.D. Addiction. 2011 Mar; 106(3): 657–669.
Most People With Addiction Simply Grow Out of It: Why Is This Widely Denied?
By Maia Szalavitz, Addictionblog.org 6/22/2015
The idea that addiction is typically a chronic, progressive disease that requires treatment is false, the evidence shows. Yet the “aging out” experience of the majority is ignored by treatment providers and journalists.
Most People With Addiction Simply Grow Out of It: Why Is This Widely Denied?
Most of Us Still Don’t Get It: Addiction Is a Learning Disorder
By Maia Szalavitz
Addiction is not about our brains being “hijacked” by drugs or experiences—it’s about learned patterns of behavior. Our inability to understand this leads to no end of absurdities.
Most of Us Still Don’t Get It: Addiction Is a Learning Disorder
5 Addiction Myths. A book review of Unbroken Brain: A Revolutionary New Way of Understanding Addiction. Laurel Sindewald, Handshake Media, 6/20/2016
Learned behavior model also explains wide array human behaviors, including political anger
Author David Brin writes
“For years I’ve followed advances that investigate reinforcement processes in the human brain, especially those involving dopamine and other messenger chemicals that are active in mediating pleasure response. One might call this topic chemically-mediated states of arousal that self-reinforce patterns of behavior.
Of course, what this boils down to — at one level — is addiction. But not only in the sense of illegal drug abuse. In very general terms, “addiction” may include desirable things, like bonding with our children and “getting high on life.” These good patterns share with drug addiction the property of being reinforced by repeated chemical stimulus, inside the brain…
Consider studies of gambling. Researchers led by Dr. Hans Breiter of Massachusetts General Hospital examined with functional magnetic resonance imaging (fMRI) which brain regions activate when volunteers won games of chance — regions that overlapped with those responding to cocaine!…
Moving along the spectrum toward activity that we consider more “normal” — neuroscientists at Harvard have found a striking similarity between the brain-states of people trying to predict financial rewards (e.g., via the stock market) and the brains of cocaine and morphine users.
… researchers at Emory University monitored brain activity while asking staunch party members, from both left and right, to evaluate information that threatened their preferred candidate prior to the 2004 Presidential election. “We did not see any increased activation of the parts of the brain normally engaged during reasoning,” said Drew Westen, Emory’s director of clinical psychology. “Instead, a network of emotion circuits lit up… reaching biased conclusions by ignoring information that could not rationally be discounted. Significantly, activity spiked in circuits involved in reward, similar to what addicts experience when they get a fix,” Westen explained.
Addicted to Self-Righteousness? An Open Letter to Researchers In the Fields of Addiction, Brain Chemistry, and Social Psychology
Indignation, addiction and hope — does it help to be “mad as hell?”: David Brin at TEDxUCSD
Fair use
This website is educational. Materials within it are being used in accord with the Fair Use doctrine, as defined by United States law.
§107. Limitations on Exclusive Rights: Fair Use
Notwithstanding the provisions of section 106, the fair use of a copyrighted work, including such use by reproduction in copies or phone records or by any other means specified by that section, for purposes such as criticism, comment, news reporting, teaching (including multiple copies for classroom use), scholarship, or research, is not an infringement of copyright. In determining whether the use made of a work in any particular case is a fair use, the factors to be considered shall include: the purpose and character of the use, including whether such use is of a commercial nature or is for nonprofit educational purposes; the nature of the copyrighted work; the amount and substantiality of the portion used in relation to the copyrighted work as a whole; and the effect of the use upon the potential market for or value of the copyrighted work. (added pub. l 94-553, Title I, 101, Oct 19, 1976, 90 Stat 2546)
Organic food and farming
Organic food
“People got in their head, well, if it’s man-made somehow it’s potentially dangerous, but if it’s natural, it isn’t. That doesn’t really fit with anything we know about toxicology. When we understand how animals are resistant to chemicals, the mechanisms are all independent of whether it’s natural or synthetic. And in fact, when you look at natural chemicals, half of those tested came out positive [for toxicity in humans].” –Bruce Ames
Organic food is food produced by organic farming, a set of techniques that mixes scientific knowledge of soil depletion and enrichment with anti-scientific beliefs and myths about nature and the natural.
A key belief of groups like the International Federation of Organic Agriculture Movements (IFOAM) and the Soil Association, which oppose conventional farming in favor of organic farming, is that pesticides and fertilizers are so harmful that they should be avoided unless they are “natural.”
This belief is contradicted by the vast majority of scientific studies that have been done on these subjects (Morris and Bate 1999; Taverne 2006; NCPA study). The United States Department of Agriculture (USDA) has put in place a set of national standards that food labeled “organic” must meet, whether it is grown in the United States or imported from other countries.
“USDA makes no claims that organically produced food is safer or more nutritious than conventionally produced food. Organic food differs from conventionally produced food in the way it is grown, handled, and processed.”*
Harm from bacterial contamination is a much greater possibility from natural fertilizers (Stossel 2005: 194). (For those of you who hate John Stossel, read the newspaper. The most dangerous bacteria in America’s food supply is E. coli, which is found in abundance in cattle manure, a favorite “natural” fertilizer of organic farming.)
The residues from pesticides on food, natural or synthetic, are not likely to cause harm to consumers because they occur in minute quantities.* (This fact does not make either kind of pesticide safe for those who work with them and are exposed to large quantities on a regular basis. I refer to residues on foods you and I are likely to find on fruits and vegetable we buy at the store or market.)
Using natural biological controls rather than synthetic pesticides is more dangerous to the environment (Morris and Bate 1999). The amounts of pesticide residue produced by plants themselves or introduced by organic farmers are significantly greater than the amounts of synthetic pesticide residues.
Almost all of the pesticides we ingest in food are naturally produced by plants to defend themselves against insects, fungi, and animal predators (Ames and Gold 1997). The bottom line is that fresh fruits and vegetables are good for you and it doesn’t matter whether they’re organic.
Over 30 separate investigations of about 500,000 people have shown that farmers, millers, pesticide-users, and foresters, occupationally exposed to much higher levels of pesticide than the general public, have much lower rates of cancer overall (Taverne 2006: 73.)
Groups like IFOAM refer to synthetic pesticides as “toxic,” even though the amount of pesticides people are likely to ingest through food are always in non-toxic amounts.
Many toxic substances occur naturally in foods, e.g.,arsenic in meat, poultry, dairy products, cereals, fish, and shellfish, but usually in doses so small as not to be worthy of concern. On the IFOAM website you will find the following message:
Although IFOAM has no official position on the quality of organic food, it’s easy to conclude that the overall nutritional and health-promoting value of food is compromised by farming methods that utilize synthetic fertilizers and toxic pesticides.
It’s easy to conclude—as long as you ignore the bulk of the scientific evidence that is available.
the myth of organic superiority
The evidence for the superiority of organic food is mostly anecdotal and based more on irrational assumptions and wishful thinking than on hard scientific evidence. There is no significant difference between a natural molecule and one created in the laboratory. Being natural or organic does not make a substance safe* nor does being synthetic make a substance unsafe.
Organic food does not offer special protection against cancer or any other disease. Organic food is not “healthier” than food produced by conventional farming, using synthetic pesticides and herbicides. Organic farming is not necessarily better for the environment than conventional farming. There is scant scientific evidence that most people can tell the difference in taste between organic and conventional foods. The bottom line is: fresher is better. Organic produce that travels thousands of miles to market is generally inferior to the same produce from local farmers, organic or not.
Is there any difference between organic and conventional fruits and vegetables? According to one scientific paper, there are several differences:
Based on the results of our literature review and experiment we conclude that there are substantial differences between organic and conventional fruits and vegetables. They differ with respect to production method, labeling, marketing, price and potentially other parameters.
You don’t need to do a scientific study to know that organic foods are produced differently from conventionally farmed foods. Anyone who has been to the market knows that you will pay substantially more for food labeled “organic.”
… The aforementioned scientific study did find that the literature provides evidence for one nutritional difference between organic and conventional foods: vitamin C was found to be higher for organic food.
coddling by the media
The way the media treat “green” issues accounts for one reason that the organic-is-better myth is pervasive. Here’s an example from BBC News:
Growing apples organically is not only better for the environment than other methods but makes them taste better than normal apples, US scientists say.
The study is among the first to give scientific credence to the claim that organic farming really is the better option.
The researchers found organic cultivation was more sustainable than either conventional or integrated farming, which cuts the use of chemicals.
The scientists, from Washington State University in Pullman, found the organic apples were rated highest for sweetness by amateur tasting panels.
They reported: “Escalating production costs, heavy reliance on non-renewable resources, reduced biodiversity, water contamination, chemical residues in food, soil degradation and health risks to farm workers handling pesticides all bring into question the sustainability of conventional farming systems.”
The headline for the story reads: Organic apples tickle tastebuds.
Most people might stop reading the story after five paragraphs of nothing but positive statements about organic farming and the mention of a number of problems ahead for conventional farming. For those who persevere, however, the following bits of information are also provided:
…organic farming systems were “less efficient, pose greater health risks and produce half the yields of conventional farming”.
…the tests “found no differences among organic, conventional and integrated apples in texture or overall acceptance”.
…Growers of more sustainable systems may be unable to maintain profitable enterprises without economic incentives, such as price premiums or subsidies for organic and integrated products.
Apparently, the measure used to determine that organic farming was “better for the environment” was based on physical, chemical, and biological soil properties. The scientists created their own index and found that organic was better mainly because of the addition of compost and mulch.
Certainly, there are going to be some organic farms that use methods of composting and mulching that improve growing conditions. But there are also methods conventional farmers can use to accomplish the same thing.
Finally, there are some organic farmers who used methods of composting and mulching that don’t improve anything except the chances of bacterial infection. Only a “green” journalist or scientist could turn being less efficient, posing greater health risks, no different in texture or appearance, and producing half the yields of conventional farming into “better than conventional farming.”
I’ll provide just one more example of how the media and scientists with agendas distort the results of scientific studies that compare organic with conventional agricultural practices. In 2003, Alyson Mitchell, Ph.D., a food scientist at the University of California, Davis, co-authored a paper with the formidable title of “Comparison of the Total Phenolic and Ascorbic Acid Content of Freeze-Dried and Air-Dried Marionberry, Strawberry, and Corn Grown Using Conventional, Organic, and Sustainable Agricultural Practices.”
The article was published in the Journal of Agricultural and Food Chemistry, a peer-reviewed journal of the American Chemical Society. The article got some good press from “green” journalists, who proclaimed that the study showed that organic foods have significantly higher levels of antioxidants than conventional foods.
(Examples of glowing press reports can be found here and here.) There is a strong belief among promoters of organic foods that there is good scientific support for the claim that diets rich in antioxidants contribute to significantly lower cancer rates.
The data, however, do not support this belief. “Study after study has shown no benefit of antioxidants for heart disease, cancer, Parkinson’s disease, Alzheimer’s disease, or longevity” (Hall 2011).
The study compared total phenolic metabolites and ascorbic acid in only two crops, marionberries and corn. Both crops were grown organically and conventionally on different farms. The organic berries were grown on land that had been used for growing berries for four years; the conventional berries were grown on land that had been used to grow conventional berries for 21-22 years.
The crops were grown on different soil types: the organic soil was “sandy, clay, loam”; the conventional was “sandy, Ritzville loam.” The soil for the conventional corn had been used before for wheat; the soil for the organic corn had been used for green beans. The conventional farm used well water; the organic farm used a combination of well and creek water. (I don’t mention the strawberry listed in the title of the article because no organic strawberries were tested.)
As you can tell from the title of the article, the metabolites measured were not taken from fresh berries or corn but from samples that had been freeze-dried and air-dried. Though not mentioned in the title, the scientists also compared samples that were simply frozen.
The data provided by the authors in their published study shows clearly that there was not enough measurable ascorbic acid (AA) in either of the marionberry samples to compare the organic to the conventional. As already noted, no organic strawberries were studied. There was not enough measurable AA for the freeze-dried or air-dried corn to be compared.
So, the only data on AA is for the frozen corn: organic had a value of 3.2 and conventional had a value of 2.1. You can read the study yourself to find out what these numbers represent, but whatever they represent they do not merit the conclusion drawn by the authors of the study: “Levels of AA in organically grown … samples were consistently higher than the levels for the conventionally grown crops.”
The study also compared what it calls “sustainable agricultural practices” to organic and conventional practices. Sustainable practices in this study included the use of synthetic fertilizers.
“Our results indicate,” the authors write, “that TPs [total phenolics] were highest in the crops grown by sustainable agricultural methods as compared to organic methods.” Dr. Mitchell is quoted in the press as saying that their study “helps explain why the level of antioxidants is so much higher in organically grown food.” Yet, her study clearly states that the evidence for this claim is anecdotal. In fact, the authors write of the comparative studies that have been done:
These data demonstrate inconsistent differences in the nutritional quality of conventionally and organically produced vegetables with the exception of nitrate and ascorbic acid (AA) in vegetables.
distortion of evidence by scientists
One thing these “green” advocates are good at is distorting data to make lead appear to be gold. Another study led by Mitchell claims that organic tomatoes have “statistically higher levels (P < 0.05) of quercetin and kaempferol aglycones” than conventional tomatoes. The increase of these flavonoids corresponds “with reduced manure application rates once soils in the organic systems had reached equilibrium levels of organic matter.”
In fact, the study suggests that it is the nitrogen “in the organic and conventional systems that most strongly influence these differences.” The authors suggest that “overfertilization (conventional or organic) might reduce health benefits from tomatoes.” The argument is that the flavonoids are a protective response by the plants and one of the things they respond to is the amount of nitrogen in the soil.
In any case, the thrust of these and similar studies is that both organic and conventional crops can be manipulated to yield higher levels of antioxidants. At least one study has found “organic food products have a higher total antioxidant activity and bioactivity than the conventional foods.”* That study, however, involved only ten Italian men, aged 30-65 years.
I have to say that I am underwhelmed by the studies I have reviewed that claim to have found organic foods are more nourishing or healthy than conventional fruits and vegetables. At present, there is no strong body of scientific evidence that supports the contention that organic fruits and vegetables are superior to conventional produce.
A best case scenario for the organic folks would be that to achieve the recommended nutrients from five helpings a day of fruits or vegetables you might have to eat four or five more conventionally grown strawberries or two or three more baby carrots to get the same amount of vitamins, minerals, or antioxidants as provided by organic fruits and vegetables. But I’m not sure the evidence supports even that weak position.
History of the term “organic”
The term ‘organic’ as a descriptor for certain sustainable agriculture systems appears to have been used first by Lord Northbourn in his book Look to the Land (1940).
“Northbourn used the term to describe farming systems that focused on the farm as a dynamic, living, balanced, organic whole, or an organism.”* T
he term ‘organic’ was first widely used in the U.S. by J. I. Rodale, founder of Rodale Press, in the 1950s. “Rodale failed to convince scientists of the validity of his approach because of his reliance on what were perceived to be outrageous unscientific claims of organic farming’s benefits.”*
The USDA standards for organic food state:
Organic food is produced without using most conventional pesticides; fertilizers made with synthetic ingredients or sewage sludge; bioengineering; or ionizing radiation.
These standards capture the essence of the organic mythology:
-
Conventional pesticides should be avoided.
-
Synthetic fertilizers should be avoided.
-
Food should not be genetically altered.
-
Food should not be subjected to ionizing radiation.
The bit about sewage sludge is there because some organic farmers follow the “law of return” as proposed by Sir Albert Howard (1873-1947), a founder and pioneer of the organic movement. He advocated recycling all organic waste materials, including sewage sludge, in farmland compost. The practice of adding human and animal feces to the soil is an ancient practice found in many cultures even today.
The fact that these cultures developed their practices without benefit of modern knowledge of such things as bacteria or heavy metals is trumped by the romantic notion that farm life was idyllic in those times and places when life expectancy was half that of today.
Rudolf Steiner, the founder of a set of superstitious agricultural practices known as biodynamics, also advocated using manure as fertilizer but it had to be prepared according to a magical formula based on his belief that cosmic forces entered animals through their horns. Steiner also romanticized farming. Commenting on some peasants stirring up manure, he said:
“I have always had the opinion … that [the peasants’] alleged stupidity or foolishness is wisdom before God [sic], that is to say, before the Spirit. I have always considered what the peasants and farmers thought about their things far wiser than what the scientists were thinking.”*
Steiner gave lectures on farming, but did no scientific research to test his ideas.
A central concept of these lectures was to “individualize” the farm by bringing no or few outside materials onto the farm, but producing all needed materials such as manure and animal feed from within what he called the “farm organism.”
Other aspects of biodynamic farming inspired by Steiner’s lectures include timing activities such as planting in relation to the movement patterns of the moon and planets and applying “preparations,” which consist of natural materials which have been processed in specific ways, to soil, compost piles, and plants with the intention of engaging non-physical beings and elemental forces. Steiner, in his lectures, encouraged his listeners to verify his suggestions scientifically, as he had not yet done.*
Steiner opposed the use of synthetic fertilizers and pesticides, not on scientific grounds but on spiritual grounds. He claimed there were “spiritual shortcomings in the whole chemical approach to farming.”* He had a mystical idea of the farm as an organism, “a closed self-nourishing system.”*
This article has been excerpted from The Skeptic’s Dictionary, http://skepdic.com/organic.html
Crystals in metals
Why do metals have the properties that they have?
Background knowledge: We first need to know what crystals are.
Solid / Liquid / Gas
Metal is a type of solid
Metal is usually an imperfect crystal
At any temperature above absolute zero, atoms vibrate, so even in solids the atoms are always somewhat in motion
Iron atoms, like many other metals, take on this shape
Body-Centered Cubic (BCC) Structure:
there are 8 atoms at the 8 corners, and one atom in the centre of the unit cell.
This structure is then repeated over and over.
“The structure of iron atoms isn’t continuous throughout the entire paper clip. When a metal cools and is transitioning from liquid to solid, its atoms come together to form tiny grains, or crystals.”
“Even though the crystalline structure does not continue from crystal to crystal, the crystals are bound to one another. In this diagram, each square represents an individual atom.”
tba
atoms held together with metallic bonds
(add pics here)
tba
Defects break the bonds
“When a metal crystal forms, the atoms try to assemble themselves into a regular pattern. But sometimes there isn’t an atom available to fill in a space, and sometimes a growing layer is halted by other growing layers.”
“There are many imperfections within each crystal, and these flaws produce weak points in the bonds between atoms. It is at these points, called slip planes, that layers of atoms are prone to move relative to adjacent layers if an outside force is applied.”
“Adding other elements to a metal can counteract the effects of the imperfections and make the metal harder and stronger. Carbon, for example, is added to iron to make steel, and tin is added to copper to make bronze.”
Atoms can slip into a new position
Slipping
Metal atoms can bend
Heat can loosen the fixed positions of metal atoms
PBS NOVA: Building on Ground Zero – The Structure of Metals
PBS NOVA: Interactive Structure of Metals
PBS NOVA: Engineering Ground Zero
Learning Standards
Massachusetts Science and Technology/Engineering Curriculum Framework
High School Chemistry
HS-PS2-6. Communicate scientific and technical information about the molecular-level structures of polymers, ionic compounds, acids and bases, and metals to justify why these are useful in the functioning of designed materials.*
PS1.A Structure of matter. That matter is composed of atoms and molecules can be used to explain the properties of substances, diversity of materials, how mixtures will interact, states of matter, phase changes, and conservation of matter. States of matter can be modeled in terms of spatial arrangement, movement, and strength of interactions between particles.
PS2.B Types of interactions. Electrical forces between electrons and the nucleus of atoms explain chemical patterns. Intermolecular forces determine atomic composition, molecular geometry and polarity, and, therefore, structure and properties of substances.
Triple point
The following is from the Learner.Org Chemistry course https://www.learner.org/courses/chemistry/about/about.html
Once the gas laws were formulated, chemists could analyze how materials transitioned from one phase to another, and how temperature and pressure affected these changes.
In 1897, a British metallurgist named Sir William Chandler Roberts-Austen (1843–1902) produced what is widely regarded as an early form of a now-common tool in chemistry and related disciplines: the phase diagram.
Modern phase diagrams show relationships between different states of matter under various combinations of temperature and pressure.
A substance can exist in two different states at once—for example, as a liquid and a gas, with molecules cycling from one state to the other.
It is also possible for a material to be both solid and liquid, with both melting and freezing taking place at its edges, or to exist as a solid and a gas.
Phase diagrams show what forms a substance will take under given temperatures and pressure levels, and where these equilibrium lines (when equal numbers of molecules are changing form in both directions) are located. (Figure 2-11)
Figure 2-11. Generic Phase Diagram for a Single Substance
© Science Media Group.
https://www.learner.org/courses/chemistry/text/text.html?dis=U&num=Ym5WdElUQS9NeW89&sec=YzJWaklUQS9OeW89
Amazing: See a flask of liquid cyclohexane brought to the brink of its triple-point:
suddenly it can boil and freeze at the same time.
A volumetric flask containing liquid cyclohexane is depressurized to a very low pressure by a turbo-molecular vacuum pump. The rapid drop in pressure results in a rapid drop in temperature, causing the substance to temporarily freeze, but the system is unstable, flirting with the triple point (a point of pressure and temperature at which a substance is simultaneously solid, liquid, and gas). The result is a fluctuation between all three states of matter, in a spectacular display of chemistry and physics in action.
http://physicsfootnotes.com/triple-point/
KaiserScience 
