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Cellular Metabolism: Respiration  (Anaerobic & Aerobic)  


I). Definition

Metabolism: All of the chemical reactions necessary to maintain life.

Stage 1: Digestion in the GI tract.

Stage 2: Glycolysis: occurs in the cytoplasm.

Stage 3: Production of ATP in the mitochondria.

bulletcoenzyme: non-protein substances associated with an enzyme. In metabolism they act as electron acceptors.

NAD+-----------------> NADH+

FAD-----------> FADH+

cellular respiration

II). Cellular Respiration (Oxidation of Glucose)

C6H12O6 + 6O2-----> 6H2O + 6CO2 + 36 ATP +heat

1). Glycolysis

Glucose------> 2 pruvic acids + 2 ATP

bulletGlycolysis occurs in the cytoplasm.
bulletAnaerobic reaction.
bulletNo Oxygen .
bulletRelease 2 ATP

2). Krebs Cycle

bulletThe Krebs Cycle occurs in the mitochondria
bulletAerobic reaction.
bulletRequires oxygen

2 Pruvic Acid -------> 6CO2 + 10 reduced coenzymes + 2 ATP


bulletThe Krebss cycle occurs twice per glucose molecule.
bullet6 carbon dioxides are released
bullet 2 ATP.
bullet10 NAD coenzymes are reduced to NADH+.

3). Electron Transport Chain

NADH-   FADH- -   2H+ and O  H2O +32 ATP

bulletThe electron transport chain occurs in the mitochondria.
bulletAerobic reaction
bulletRequires oxygen
bullet32 ATP released


High energy electrons are removed from the hydrogen leaving H+ ions and received by oxygen.

The oxygen and hydrogen ions combine forming water.

As the electrons are passed down the system their energy is released to allow the build up of ATP.


III). Fermentation

What happens if oxygen is not present?

No Oxygen  =   no electron transport chain

bulletFermentation is an anaerobic process
bulletNo oxygen needed
bulletProduce 2 ATP per pyruvate

Step 1:  Glycolysis produces 2 pyruvate acids and the coenzyme NAD picks up 2 hydrogens.

Step 2    NADH2 passes its hydrogens to pyruvate and forms lactic acid.

2ADP + Pyruvate + NADH2------

2 ATP + Lactate + NAD



This is a representation of the workings of the Krebs Cycle