Energy for action topic 7/a=respiration

Question 1

What is the final product formed in glycolysis?

1

Answer 1

Pyruvate.

Question 2

Glucose needs to be made more reactive before it can be split into two molecules, explain how this activation of glucose occurs.
(2)

Answer 2

• Phosphate is added/phosphorylation of glucose.

- from breakdown of ATP.

Question 3

Describe the changes occurring in glycolysis during the conversion of intermediate compound 3C to pyruvate.
(2)

Answer 3

• Dehydrogenation/hydrogen released.
• Attaches to NAD.
• Forming reduced NAD.
• Formation of ATP/ via substrate level phosphorylation of ADP.

Question 4

A glycogen molecule may contain 60,000 glucose units. If 60,000 glucose molecules undergo glycolysis,

• How many molecules of ATP would produced in total (at end of (glycolysis)?
• What would be the net gain of ATP?
• How many hydrogen atoms would be produced?
• How many pyruvate?

Answer 4

• 60,000 x 4 ATP = 240,000
• 60,000 x 2 ATP = 120,000 (2 used in activation of glucose)
• 60,000 x 2 H = 120,000
• 60,000 x 2 Pyruvate = 120,000

Question 5

Why is the synthesis of ATP via the electron transport chain termed ‘oxidative phosphorylation’?

Answer 5

• Due to the series of redox reactions (oxidation-reduction) occurring as the electrons pass along the electron transport chain; the final electron acceptor is oxygen.
• Phosphate is added to ADP to form ATP, using ATPase, during chemiosmosis.
• Losing energy.

Question 6

Suggest why the link reaction and the Krebs cycle take place inside the mitochondria.

Answer 6

-Since the electron carries, ETC and ATP synthase are situated inside the inner mitochondrial membrane. This arrangement allows for an organised and sequenced series of steps, resulting in mass production of ATP, than if the reaction took place in the cytoplasm.

Question 7

Where does glycolysis occur?

Answer 7

Cytoplasm.

Question 8

Where does the link reaction occur?

Answer 8

Mitochondrial matrix.

Question 9

Where does the Krebs cycle occur?

Answer 9

Mitochondrial matrix.

Question 10

Where is the electron transport chain?

Answer 10

Inner mitochondrial membrane.

Question 11

Suggest what would happen to the Krebs cycle if acetyl coA became unavailable.
(3)

Answer 11

• Krebs cycle would stop.
• 6 carbon compound would not be synthesised.
• 5 carbon compound would not be synthesised.
• Co2 and H reduced.

Question 12

Describe the fate of reduced NAD in aerobic respiration.

4

Answer 12

• Reduced NAD from glycolysis enters mitochondria.
• Moves to inner membrane of mitochondrion.
• Becomes oxidised NAD+.
• As electrons transferred to electron transport chain.
• Hydrogen ions pumped into membrane space.
• NAD returns to Krebs cycle/matrix.

Question 13

What are the two types of anaerobic respiration?

Answer 13

• Ethanol fermentation- takes place in plants and yeast.

- Lactate fermentation- takes place in animals.

Question 14

What stage do both types of respiration (aerobic and anaerobic) start with?

Answer 14

-Glycolysis.

Question 15

What is the net gain of glycolysis?

Answer 15

-2ATP molecules and 2NADH molecules.

Question 16

How many ATP are synthesised per reduced NAD and reduced FAD.

Answer 16

• R. NAD =3

- R. FAD =2

Question 17

Summarise anaerobic respiration.

Answer 17

• Pyruvate is reduced to lactate.
• This reaction is catalysed by lactate dehydrogenase.
• Reduced NAD is oxidised to NAD.

Question 18

What is the net gain from the link reaction?

Answer 18

• 1 CO2 molecule.

- 1 reduced NAD.

Question 19

What is the net gain of the Krebs cycle?

Answer 19

• 2 co2 molecules.
• 3 reduced NAD.
• 1 ATP via substrate level phosphorylation.
• 1 reduced FAD.

Question 20

What are the stages in oxidative phosphorylation?

Answer 20

• Oxidation of reduced NAD and reduced FAD by the first electron carrier.
• Transfer of electrons along the ETC.
• Establishment of the electrochemical/proton gradient.
• Chemiosmosis.
• Accepting of electrons by oxygen.

Question 21

Why does anaerobic respiration produce far less ATP then aerobic respiration?

Answer 21

• Anaerobic respiration relies on substrate level phosphorylation in the glycolytic pathway to produce a net 2ATP per glucose.
• Aerobic respiration produces 2ATP from substrate level phosphorylation in glycolysis, 2ATP from substrate level phosphorylation in the Krebs cycle and around 32 ATP from oxidative phosphorylation.

Question 22

Anaerobic respiration regenerates a molecule which is essential for the continuation of substrate-level phosphorylation when there is no oxidative phosphorylation.

What is this molecule?

Answer 22

NAD