5.7

Question 1

Explain steps in glycolysis.

Answer 1

1) Glucose phosphorylated twice to form hexose biphopshate.
2) This is broken down into two molecules of Triose phosphate.
3) This is reduced into two molecules of pyruvate

Question 2

How does pyruvate enter the mitochondrial matrix?

Answer 2

pyruvate-H+ symport

Question 3

Products of glycolysis are?

Answer 3

• 2 Molecules of ATP but 2 used to kickstart - 2 gained
• 2 reduced NAD
• 2 pyruvate molecules

Question 4

What occurs during Link reaction?

Answer 4

1) Carboxyl group is removed and origin of some of the carbon dioxide produced.
2) Decarboxylation and dehydrogenation together cause pyruvate to produce an acetyl group
3) Acetyl group combines with coenzyme A to be acetyl co enzyme A
4) NAD is reduced
5) Acetyl group is transported to Krebs Cycle in the form of Acetyl Co enzyme A

Question 5

What occurs during Krebs Cycle?

Answer 5

1) Acetyl group released and bonds with oxaloacetate to form citrate
2) Citrate decarboxylated and dehydrogenated to produce 4 carbon compound, reduced NAD and carbon dioxide
3) 4 carbon compound then binds temporarily to coenzyme A where by substate level phosphorylation takes place to produce ATP.
4) Then it is dehydrogenated producing another 4 carbon compound and reduced FAD.
5) Then converted back into oxaloacetate.

Question 6

Explain process of oxidative phosphorylation?

Answer 6

1) Reduced NAD and reduced FAD are reoxidises delivering hydrogen atom to electorn transport chain
2) Hydrogen atom splits into electrons and protons
3) Protons diffuse into inter-membrane space using ATP
4) Each electron carrier protein has an iron ion (co factor) which accepts electron becoming and then reoxidises by donating to next electron carrier
5) ATP produced used to pump protons from Matrix into inter-membrane space
6) Protons accumulate forming gradient which flows across ATP synthase enzyme to produce ATP by combine ADP and phosphate group
7) Final electron acceptor is oxygen which combines with electrons and protons to form water

Question 7

Describe the ethanol fermentation pathway?

Answer 7

1) Pyruvate produced during glycolysis is decarboxylated into ethanol (pyruvate decarboxylase)
2) Ethanol accepts hydrogen atoms from reduced NAD becoming reduced ethanol
3) Reduced NAD reoxidises to accept hydrogen atoms from triose phosphate allowing glycolysis to continue

Question 8

Describe lactate fermentation pathway?

Answer 8

1) Pyruvate produced during glycolysis accepts hydrogen atoms from reduced NAD

2) Pyruvate is reduced to lactate
Reduced NAD becomes reoxidises

3) Reoxidises NAD can accept more hydrogen atoms from triose phosphate to continue ATP production

Question 9

What happens to lactate?

Answer 9

• Recycled to glucose and glycogen

- Converted to pyruvate to continue in Krebs Cycle