Basic Overview

Glucose is broken down and has its energy extracted in cellular respiration. The first stage of cellular respiration occurs in the cytoplasm, while the second and third stages occur in mitochondria. In cellular respiration, electrons are transferred from glucose to coenzymes such as NAD+ and finally to oxygen; the energy released by this relocation of electrons is used to make ATP. Carbon dioxide and water are given off as byproducts.


38 is the maximum number of ATP that can be formed although some books state that the correct number is 36. This difference is because some biologists argue that 2 ATP are used to transport the 2 pyruvate from the cytoplasm into the mitochondria (glycolysis - Kreb's cycle).

Summary of ATP Produced

citric acid cycle
electron transport chain
10 NADH+H+ ----> 30 ATP (1NADH+H+ = 3ATP)
2 FADH2 ----> 4 ATP (1FADH2 = 2 ATP)
total etc ----> 34 ATP
Total ATP during cellular respiration
38 ATP* (see note on left side of page)

Key words for cellular respiration

catabolism- breaks molecules down which in turn releases energy.
anabolism- builds molecules and makes bonds which store energy.
oxidation- loses an electron.
reduction- gains an electron.

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