Cellular Respiration

Question 1

What is glycolysis?

Answer 1

Glycolysis is the breakdown of glucose to pyruvate in the cytoplasm.

Question 2

Explain ATP in cellular respiration.

Answer 2

ATP is required for the phosphorylation of glucose and intermediates during the energy investment phase of glycolysis. This leads to the generation of more ATP during the energy pay-off stage and results in a net gain of ATP.

Question 3

Describe pyruvate in aerobic conditions?

Answer 3

In aerobic conditions, pyruvate is broken down to an acetyl group that combines with coenzyme A forming acetyl coenzyme A.

Question 4

Explain the citric acid cycle?

Answer 4

In the citric acid cycle the acetyl group from acetyl coenzyme A combines with oxaloacetate to form citrate. During a series of enzyme-controlled steps, citrate is gradually converted back into oxaloacetate which results in the generation of ATP and release of carbon dioxide.

Question 5

Describe dehydrogenase.

Answer 5

Dehydrogenase enzymes remove hydrogen ions and electrons and pass them to the coenzyme NAD, forming NADH. This occurs both glycolysis and the citric acid cycle.

Question 6

What happens to the hydrogen ions and electrons from NADH.

Answer 6

The hydrogen ions and electrons from NADH are passed to the electron transport chain on the inner mitochondrial membrane.

Question 7

Explain ATP synthesise?

Answer 7

• Electrons are passed along the electron transport chain releasing energy.
• This energy allows hydrogen ions to be pumped across the inner mitochondrial membrane. The flow of these ions back through the membrane protein ATP synthase results in the production of ATP.
• Finally, hydrogen ions and electrons combine with oxygen to form water.

Question 8

Fermentation

Answer 8

• In the absence of oxygen, fermentation takes place in the cytoplasm.
• In animal cells, pyruvate is converted to lactate in a reversible reaction.
• In plant and yeast, ethanol and CO2 are produced in an irreversible reaction.
• Fermentation results in much less ATP being produced than in aerobic respiration.

Question 9

The role of ATP in the transfer of energy.

Answer 9

ATP is used to transfer energy to cellular processes which require energy.

Question 10

Describe what is meant by the ‘Electron Transport Chain’?

Answer 10

The Electron Transport Chan is a series of Carrier Proteins attached to the inner mitochondrial membrane.