18.1 Glyolysis

Question 1

What are coenzymes? Which ones are used in respiration?

Answer 1

A coenzyme is a molecules that aids the function of an enzyme by transferring a chemical group from one molecule to another.
Co-enzymes used in respiration include NAD, coenzymes A, and FAD

NAD and FAD transfer hydrogen from one molecule to another. This means the can reduce (give hydrogen to) or oxidise (take hydrogen from) a molecule

Coenzyme A transfers acetate between molecules

Question 2

What are the four stages of aerobic respiration?
Where do they take place?

Answer 2

1) Glycolysis
2) The link reaction
3) Krebs cycle
4) Oxidative phosphorylation

The first three stages are a series of reactions. The products from these are used in the final stage to produce ATP

The first stage happens in the cytoplasm, and the other stages take place in the mitochondria

Question 3

Describe glycolysis

Answer 3

• occurs in the cytoplasm of the cell
• anaerobic process
• glucose (6C) is split into two pyruvate molecules (2 X 3C).
• first stage of both aerobic and anaerobic respiration
• two stages in glycolysis - phosphorylation and oxidation
• first ATP is used to phosphorylate glycogen into triose phosphate
  Phosphorylation is the process of adding phosphate to a molecule.
• then triose phosphate is oxidised, releasing ATP

Overall there’s a net gain of 2 ATP

Question 4

Describe and explain phosphorylation stage of glycolysis

Answer 4

Glucose is phosphorylated by adding a phosphate from a molecule of ATP.
This creates one molecule of hexose phosphate and molecule of ADP.

Hexose phosphate is then phosphorylated by ATP to form hexose bisphosphate and another ADP molecule.

Then hexose bisphosphate (unstable compound is split into 2 molecules of triose phosphate

Question 5

Describe and explain the oxidation stage of glycolysis

Answer 5

• triose phosphate is oxidised (loses hydrogen), forming two molecules of pyruvate
• NAD, coenzymes, collects the hydrogen ions, forming 2 reduced NAD.
• 4 ATP are produced, but 2 were used up in stage one, so there’ s a net gain of 2 ATP

Question 6

What are the products of glycolysis?
Where do they go?

Answer 6

• 2 reduced NAD (goes to oxidative phosphorylation)
• 2 pyruvate (to the link reaction)
• 2 ATP [net gain] (used for energy)