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Synthesizing organic molecules

Synthesize: to form by combining parts.

Our body bonds smaller molecules together to form larger molecules. This is termed synthesis.


Small pieces                           Put together, sugars make

Sugars                                     Carbohydrates, or fiber

Digestion of Carbohydrates

Starch is a carbohydrate made of a large number of glucose units, bonded together. Has to be broken down into single sugar units to be absorbed.

1. Mouth (chewing, and enzymes in saliva)

2. Esophagus (tube connects mouth to stomach)

3. Stomach (acid kills bacteria, enzymes do more digestion)

4. Small intestine (more enzymes totally digest food)

5. In the intestine, broken-down molecules are so tiny, that they pass through the intestine wall, into the bloodstream

6. Once in blood, molecules travel to all cells in the body, where they are used.


Sources of Carbohydrate

from http://dtc.ucsf.edu/living-with-diabetes/diet-and-nutrition/understanding-carbohydrates/

Carbohydrates are found in:

Rice, grains, cereals, and pasta, breads, tortillas, crackers, bagels and rolls

Dried beans, split peas and lentils

Vegetables, like potatoes, corn, peas and winter squash

Fruit, Milk, Yogurt, Sugars (like table sugar and honey)

Foods and drinks made with sugar, like regular soft drinks and desserts


Our small intestine has enzymes that can digest (break apart) many carbohydrates into their component sugars, but not all. Those plant carbs that our body can not break down are termed fiber.

What determines whether our enzymes can digest them The conformation of the chemical bonds between their sugars  (glycosidic bonds).

Humans lack digestive enzymes capable of hydrolyzing (breaking apart) most β-glycosidic bonds, which explains why amylose, a glucose polymer with α-1,4 glycosidic bonds, is digestible by human enzymes, while cellulose, a glucose polymer with β-1,4 glycosidic bonds, is indigestible (Figure 1).

{Linus Pauling Institute -Micronutrient Information Center}

Found in fruit, vegetables and whole grains. Many forms of fiber have near-zero calories.





Fat synthesis

Small pieces                             Put together, these molecules make

Glycerol + Fatty Acids             Triglycerides ( a type of oil, or fat)

Triacylglycerols (triglycerides) = major energy reserve for plants and animals.



Synthesis of DNA

There are biochemical pathways by which cells bring C, H, O, N atoms into purines (e.g. adenine and guanine) and pyrimidines  (e.g. cytosine, thymine, and uracil.) We’ll just show you the finished product:

The main building blocks of deoxy ribo nucleic acid

Yet these small molecules are just monomers – the cell bonds them together into longer units, polymers, called genes.

Then DNA nucleotides are synthesized into genes


Synthesis of proteins

Amino acids (monomers) are synthesized into peptides, or proteins (polymers)

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.

Many amino acids join together to form a peptide (small protein)



Proteins then fold into coils and sheets. They become biological machines. Their shape determines their function (“job”.)


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