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Here are some typical organisms (forms of life on Earth.)

Organisms are made of tissues

Tissues are made of cells

There are many types of tissues in animals, and in plants.

Cells are the basic unit of life.

A cell is the smallest unit that can truly be called living.

Most cells are so small that they can only be seen with a microscope.

Animal cell versus plant cell

We can see that inside cells there are smaller parts.

These are called organelles. They are tiny biological machines.

Each organelle has its own job. Examples include the nucleus, ribosome, mitochondria, Golgi, etc.

Let’s take a closer look at this.

Characteristics of Life

Organelles, an introduction

Organelles: In more depth

Let’s look at what goes on inside a cell

What is the role of enzymes in cells?



Endocytosis and exocytosis

Let’s look at single-celled organisms



How do cells reproduce?

The cell cycle


Asexual reproduction


Honors Biology

Active transport across cell membranes

Ion channels and carrier proteins

Endosymbiosis: origin of eukaryotic cells from prokaryotes

Size and scale

The amazing cell and DNA size and scale app!

Cells – how big? from a hair down to a virus

Interactive scale of the Universe (No, really, the entire known scale!)

Numbersleuth magnifying the Universe

Powers of 10: Molecular Expressions from FSU

If the moon were only 1 pixel: A tediously accurate scale model of the solar system 😉

Nikon Universcale

Powers of Ten (1977) by Charles and Ray Eames


Virtual labs

PhET membrane channels app

Serendip diffusion applet


Sample questions

Feb 2016 MCAS. Beginning with one parent cell, how many daughter cells are typically produced from one mitotic division?
A. 1 .   B. 2 .    C. 4 .   D. 8


Learning Standards

Massachusetts Curriculum Frameworks: Biology

6.MS-LS1-1. Provide evidence that all organisms (unicellular and multicellular) are made of cells.

6.MS-LS1-2. Develop and use a model to describe how parts of cells contribute to the cellular functions of obtaining food, water, and other nutrients from its environment, disposing of wastes, and providing energy for cellular processes.

Disciplinary Core Idea Progression Matrix: LS1.A Structure and function

Grades 6-8: All living things are made up of cells. An organism can be made of one cell
(unicellular) or many cells (multicellular). Within cells, specialized structures are responsible for specific functions. In multicellular organisms, cells work together to form tissues and organs that are specialized for particular body functions.

Grades 9-10: Systems of specialized cells within organisms carry out essential functions of life. Any one system in an organism is made up of numerous parts. Feedback mechanisms maintain an organism’s internal conditions within certain limits and mediate behaviors.

College Board Standards for College Success in Science

LS.2.1 Cell Function – Students understand that cells perform the essential functions of life, such as energy transfer and transformation, exchange of gas, disposal of waste, growth, reproduction, and interaction with the environment.
LS.2.2 Cell Structure – Students understand that cells have internal structures that carry out specialized life functions, and that these internal structures vary depending on a cell’s function.
LS.2.3 Cell Growth and Repair – Students understand that cells of multicellular organisms repeatedly divide to make more cells for growth and repair.
LS.2.4 Cell Differentiation – Students understand that in multicellular organisms, the single cell (zygote)

Common Core ELA

English Language Arts Standards » Science & Technical Subjects » Grade 9-10

Determine the meaning of symbols, key terms, and other domain-specific words and phrases as they are used in a specific scientific or technical context relevant to grades 9-10 texts and topics.

Analyze the structure of the relationships among concepts in a text, including relationships among key terms (e.g., force, friction, reaction force, energy).

Translate quantitative or technical information expressed in words in a text into visual form (e.g., a table or chart) and translate information expressed visually or mathematically (e.g., in an equation) into words.

Benchmarks for Science Literacy

American Association for the Advancement of Science

By the end of the 8th grade, students should know that

All living things are composed of cells, from just one to many millions, whose details usually are visible only through a microscope. 5C/M1a
Different body tissues and organs are made up of different kinds of cells. 5C/M1b
The cells in similar tissues and organs in other animals are similar to those in human beings but differ somewhat from cells found in plants. 5C/M1c
Cells repeatedly divide to make more cells for growth and repair. 5C/M2a
Various organs and tissues function to serve the needs of all cells for food, air, and waste removal. 5C/M2b
Within cells, many of the basic functions of organisms—such as extracting energy from food and getting rid of waste—are carried out. 5C/M3a
The way in which cells function is similar in all living organisms. 5C/M3b
About two thirds of the weight of cells is accounted for by water, which gives cells many of their properties. 5C/M4

By the end of the 12th grade, students should know that

Every cell is covered by a membrane that controls what can enter and leave the cell. 5C/H1a
In all but quite primitive cells, a complex network of proteins provides organization and shape and, for animal cells, movement. 5C/H1b
Within the cells are specialized parts for the transport of materials, energy capture and release, protein building, waste disposal, passing information, and even movement. 5C/H2a
In addition to the basic cellular functions common to all cells, most cells in multicellular organisms perform some special functions that others do not. 5C/H2b
The work of the cell is carried out by the many different types of molecules it assembles, mostly proteins. Protein molecules are long, usually folded chains made from 20 different kinds of amino acid molecules. The function of each protein molecule depends on its specific sequence of amino acids and its shape. The shape of the chain is a consequence of attractions between its parts. 5C/H3

The genetic information encoded in DNA molecules provides instructions for assembling protein molecules. 5C/H4a
The genetic information encoded in DNA molecules is virtually the same for all life forms. 5C/H4b
Before a cell divides, the instructions are duplicated so that each of the two new cells gets all the necessary information for carrying on. 5C/H4c
Complex interactions among the different kinds of molecules in the cell cause distinct cycles of activities, such as growth and division. Cell behavior can also be affected by molecules from other parts of the organism or even other organisms. 5C/H5
Gene mutation in a cell can result in uncontrolled division called cancer. Exposure of cells to certain chemicals and radiation increases mutations and thus the chance of cancer. 5C/H6

Most cells function best within a narrow range of temperature and acidity. At very low temperatures, reaction rates are too slow. High temperatures and/or extremes of acidity can irreversibly change the structure of most protein molecules. Even small changes in acidity can alter the molecules and how they interact. 5C/H7
A living cell is composed of a small number of chemical elements mainly carbon, hydrogen, nitrogen, oxygen, phosphorous, and sulfur. Carbon, because of its small size and four available bonding electrons, can join to other carbon atoms in chains and rings to form large and complex molecules. 5C/H8
Some protein molecules assist in replicating genetic information, repairing cell structures, helping other molecules get in or out of the cell, and generally catalyzing and regulating molecular interactions. 5C/H9** (SFAA)


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