Unit 2 Key area 2

Question 1

define the term glycolysis?

Answer 1

glycolysis is the breakdown of glucose in the cytoplasm to form pyruvate.

Question 2

Write notes on the process of glycolysis?

Answer 2

• ATP is required for the phosphorylation of glucose and other intermediates during the energy investment stage.
• Later on ATP will be produced in the energy payoff stage
• This will result in the net gain of 2ATP molecules
• This process occurs in the absence of oxygen
• This process occurs in the cytoplasm
• Pyruvate is produced.
• If oxygen is present pyruvate is sent on with ATP to the citric acid cycle
• Dehydrogenase enzymes remove hydrogen ions and high energy electrons and pass them on to the coenzymes NAD to form NADH which then goes to the electron transport chain on the inner mitochondrial membrane.

Question 3

Write notes on the citric acid cycle?

Answer 3

• Pyruvate is broken down into an acetyl group which reacts with coenzyme A to form acetyl-coA. Carbon dioxide is released
• This process occurs in aerobic conditions (requires oxygen)
• The acetyl group from the acetyl-coA “combines” with oxaloacetate to from citrate.
• During a series of enzyme controlled steps citrate is converted back into oxaloacetate
• This results in the generation of ATP and the release of more carbon dioxide
• This process occurs in the matrix of the mitochondria
• Dehydrogenase enzymes remove hydrogen ions and high energy electrons and pass them on to the coenzymes NAD to form NADH which then goes to the electron transport chain on the inner mitochondrial membrane.

Question 4

Write notes on the electron transport chain?

Answer 4

• High energy electrons are passed along the electron transport chain releasing energy.
• The electron transport chain is located in the inner mitochondrial membrane
• The energy released allows for hydrogen ions to be pumped across the inner mitochondrial membrane. This movement of hydrogen ions through the enzyme ATP synthase, results in the production of ATP molecules.
• Hydrogen Ions and electrons combine with oxygen to form water

Question 5

Where in a cell would fermentation take place?

Answer 5

In the cytoplasm

Question 6

Describe the process of fermentation in animals?

Answer 6

Fermentation occurs in the absence of oxygen in animals and results in the production of lactate in a reversible reaction

(fermentation itself does not produce ATP, ATP is produced in the glycolysis stage beforehand)

Question 7

Describe fermentation in plants?

Answer 7

In plants fermentation takes place and produces ethanol and carbon dioxide in an irreversible reaction.

Question 8

Why is fermentation not the standard method of cellular respiration in animals?

Answer 8

As aerobic respiration has a much higher yield of ATP than the glycolysis stage on its own.