Online College Courses for Credit

Cell Respiration

Cell Respiration

Author: Jessica Libby


To determine what happens and what is made during the three stage of cellular respiration.

To differentiate between aerobic and anaerobic respiration.

To explain how ATP is formed in substrate level phosphorylation and oxidative phosphorylation.

See More
Fast, Free College Credit

Developing Effective Teams

Let's Ride
*No strings attached. This college course is 100% free and is worth 1 semester credit.

29 Sophia partners guarantee credit transfer.

314 Institutions have accepted or given pre-approval for credit transfer.

* The American Council on Education's College Credit Recommendation Service (ACE Credit®) has evaluated and recommended college credit for 27 of Sophia’s online courses. Many different colleges and universities consider ACE CREDIT recommendations in determining the applicability to their course and degree programs.


Respiration Review

Here is a basic overview of cell respiration.


Respiration involves oxidative-reduction reactions (redox). An electron moves from one reactant to another. The reactant that loses an electron (and energy) is oxidized; the reactant that gains an electron (and energy) is reduced. In respiration, electrons are taken from the glucose (along with a H proton) and move to an electron carrier such as NAD+. NAD+ is reduced and takes in two electrons and a H proton (H+) to become NADH.

Glycolysis is considered to be substrate level phosphorylation. This means that a substrate donate a phosphate to ADP to make ATP.  The electron transport chain is oxidative phosphorylation which is when electrons give up energy to form ATP.

Electron Transport Chain

The electron transport chain consist of 3 transmembrane proteins embedded in the inner membrane. These transmembranes act hydrogen pumps to push H+ from the matrix into intermembrane space. There are also two carrier molecules that work to move electrons between the proteins. Electrons are dropped off from NADH at the first protein and from FADH2 at the first carrier molecule. As the electrons move through the chain they lose energy which is used to pump the hydrogen through the transmembrane proteins (hydrogen pumps). A high concentration of H+ is formed in the intermembrane space; H+ move back to the lower concentration through the ATP synthase which will phosphorylate ADP into ATP. Turing the potential energy from a H+ concentration into usable ATP is called chemiosmosis. 

Source: Holtzclaw, Fred, and Theresa Holtzclaw. AP Test Prep Series. San Francisco: Pearson Education Inc., 2013. 81-82. Print.,

Net Production

Glycolysis = 2 ATP, 2 NADH, 2 pyruvate

​Transition step = 2 acteyl CoA, 2 CO2, 2 NADH

Krebs/citric acid cycle = 4 CO2, 6 NADH, 2 FADH2, 2 ATP

Electron transport chain = 26-30 ATP, 6H2O