On Demand

Macromolecules

There's an old saying, "You are what you eat." In some senses, this is literally true! When we eat food, we take in the large biological molecules found in the food, including...

Khan Academy

On Demand

Energy and enzymes

You, like other living systems, are an amazing energy transformer. As you move your eyes to read these words, your body is busily converting chemical energy from your lunch into...

Khan Academy

On Demand

Structure of a cell

You, my friend, are made up of cells. Lots and lots of them. Some of them are eukaryotic (human), but many more of them are prokaryotic, thanks to the friendly bacteria of your...

Khan Academy

On Demand

Membranes and transport

How do the cells in your body define their boundaries (and control what comes in or goes out)? As it turns out, cells have a sophisticated and flexible barrier, the plasma...

Khan Academy

On Demand

Photosynthesis

There's a lot of carbon in your body - in DNA, proteins, carbohydrates, fats, and other key biological molecules. How did that carbon get there? Drumroll... photosynthesis! Learn...

Khan Academy

On Demand

Cell signaling

Did you know that your cells are continually "talking" to one another? Cells communicate by sending and receiving chemical signals. This molecular conversation allows the cells in...

Khan Academy

On Demand

Cell division

All living things, including you, are made up of cells. Find out how cells divide through mitosis and meiosis, how the cell cycle is controlled, and how problems in cell cycle...

Khan Academy

On Demand

Classical and molecular genetics

Have you ever been told that you have your mother's eyes or grandfather's nose? Learn why traits run in families and how they're passed on. We'll look at Mendel's model of...

Khan Academy

On Demand

DNA as the genetic material

What exactly is DNA? This seemingly simple polymer, made up of just four different types of monomers, serves as the genetic material for all living organisms. For example, your...

Khan Academy

On Demand

Evolution and the tree of life

Discover the diversity of life on Earth and the forces that shape it! In this section, you can learn about evolution, natural selection, and the tree of life, as well as basic...

Khan Academy