ATP and the aerobic energy system

Overview

ATP and its breakdown, glycolysis, the Krebs cycle, beta oxidation and the electron transport chain, ATP yield, fat as a fuel, and the system's advantages and disadvantages.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   What is ATP?

   Model answer

   ATP (adenosine triphosphate) is the only direct source of energy for muscle contraction. ATP is made of adenosine and three phosphate groups.

2. 2

   How is energy released from ATP?

   Model answer

   The enzyme ATPase breaks ATP down into ADP and a phosphate. Energy is released for muscle contraction.

3. 3

   Why must ATP be continually resynthesised during exercise?

   Model answer

   Muscles store only enough ATP for about 2 to 3 seconds of maximal work. ATP must be rebuilt from ADP and phosphate as fast as it is used.

4. 4

   Where does glycolysis take place, and what does it produce?

   Model answer

   Glycolysis takes place in the sarcoplasm of the muscle cell. Glucose is broken down into pyruvic acid, releasing enough energy to make 2 ATP.

5. 5

   Which enzyme breaks glycogen down to glucose, and which controls glycolysis?

   Model answer

   Glycogen phosphorylase breaks glycogen down to glucose. Phosphofructokinase (PFK) controls the breakdown of glucose to pyruvic acid.

6. 6

   What happens to pyruvic acid when oxygen is available?

   Model answer

   Pyruvic acid combines with coenzyme A to form acetyl coenzyme A. Acetyl coenzyme A then enters the Krebs cycle in the mitochondria.

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