Cellular respiration

This course is a part of Biology, a 31-course Topic series from Khan Academy.

How do your cells extract energy from the food that you eat? As it turns out, cells have a network of elegant metabolic pathways dedicated to just this task. Learn more about cellular respiration, fermentation, and other processes that extract energy from fuel molecules like glucose.

This course contains 6 segments:

Introduction to cellular respiration

How does your body get usable energy from the snack you just ate? Learn the basics of how cells extract energy from fuel molecules, including what redox reactions are and why they are important in the breakdown of fuels.

Steps of cellular respiration

Before you jump into the nitty-gritty details, get the big picture of cellular respiration. Learn about the different stages of this process and how they fit together.

Glycolysis

The name glycolysis means "sugar-splitting," and sure enough, this metabolic pathway splits glucose into two three-carbon molecules. Learn more about the steps of glycolysis and how it is used in both cellular respiration and fermentation.

Pyruvate oxidation and the citric acid cycle

Glycolysis can extract a bit of the energy from a glucose molecule, but the citric acid cycle can squeeze out much more. Learn about the steps of the cycle, how it harvests energy, and how it's fueled by acetyl CoA (produced by oxidation of pyruvate from glycolysis).

Oxidative phosphorylation

Oxidative phosphorylation produces most of the ATP made in cellular respiration. Learn more about how oxidative phosphorylation uses electron transport to drive ATP synthesis.

Variations on cellular respiration

There's more than one way to extract energy from a fuel molecule! Learn how cells break down fuels without oxygen, how non-glucose molecules can enter cellular respiration, and how cellular respiration is regulated.