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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.

• anaerobic
• aerobic
• coenzyme: non-protein substances associated with an enzyme. In metabolism they act as electron acceptors.

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

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

II). Cellular Respiration (Oxidation of Glucose)

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

1). Glycolysis

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

• Glycolysis occurs in the cytoplasm.
• Anaerobic reaction.
• No Oxygen .
• Release 2 ATP

2). Krebs Cycle

• The Krebs Cycle occurs in the mitochondria
• Aerobic reaction.
• Requires oxygen

• The Krebss cycle occurs twice per glucose molecule.

• 6 carbon dioxides are released
•  2 ATP.
• 10 NAD coenzymes are reduced to NADH+.

3). Electron Transport Chain

NADH- à  FADH- à - à  2H+ and Oà  H2O +32 ATP

• The electron transport chain occurs in the mitochondria.
• Aerobic reaction
• Requires oxygen
• 32 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.

What happens if oxygen is not present?

No Oxygen  =   no electron transport chain

• Fermentation is an anaerobic process
• No oxygen needed
• Produce 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.