VI - Kennesaw State University



Glycolysis and Respiration

A. The Catabolism of Carbohydrates

1. Glycolysis

□ Partial oxidation of glucose to form pyruvic acid.

□ A small amount of ATP is made.

□ Some NAD is reduced to form NADH.

□ The major glycolytic pathway in cells is the Embden-Meyerhoff-Parnas pathway

2. Fermentation and Respiration: Two Possible Fates of Pyruvic Acid

Examples of Fermentation: Lactic Acid Fermentation, Ethanol Fermentation

2. Fermentation & Respiration: Two Possible Fates for Pyruvic Acid

Carbohydrate in Medium

Transport proteins in Cell Wall

or Plasma Membrane

Carbohydrate inside Cell

Various Enzymes

Glucose or other Glycolytic Intermediates

Glycolysis

Pyruvic Acid (Partially oxidized)

Two Possible Fates of Pyruvic Acid

Fermentation OR Respiration

Pyruvic acid is reduced to: Pyruvic acid is oxidized

a reduced organic acid completely to CO2

(for example, lactic acid or

mixed acids)

or an alcohol

(for example, ethanol or

butanediol)

Gases (CO2 or H2) may

be produced

Final electron acceptor is Final electron acceptor is

the organic derivative an inorganic molecule,

of pyruvic acid almost always O2,

but some bacteria use

nitrate, sulfate, or sulfur

Oxygen is not required Oxygen is usually required

No additional ATP are made Additional ATP are made

3. Stages of Respiration

a. Preliminary Reaction: Pyruvic Acid is converted to Acetyl CoA and CO2

b. The Citric Acid Cycle (Krebs Cycle):

The acetyl group is completely oxidized to CO2, with the formation of NADH and FADH

c. The Respiratory Transport Chain:

The energy in NADH and FADH is converted into ATP; NAD and FAD are regenerated.

B. The Regulation of Glucose Metabolism

1. Allosteric Regulation of Phosphofructokinase

2. Glycogen Synthesis

3. Fatty Acid Synthesis

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