Respiration

Question 1

4 main stages in aerobic respiration and where they occur

Answer 1

Glycolysis: cytoplasm
Link reaction: mitochondrial matrix
Krebs cycle: mitochondrial matrix
Oxidative phosphorylation via ETC: membrane of cristae

Question 2

Stages of glycolysis

Answer 2

1. Glucose is phosphorylated to glucose phosphate by 2X ATP
2. Glucose phosphate splits into 2X triose phosphate (TP)
3. 2X TP is oxidised to 2x pyruvate
   Net gain of 2x NADH & 2x ATP per glucose

Question 3

What happens during link reaction?

Answer 3

1. Oxidation of pyruvate to acetate
   Per pyruvate molecule: net gain of 1xCO2 (decarboxylation) & 2H atoms (used to reduce 1xNAD)
2. Acetate combines with coenzyme A (CoA) to form acetylcoenzyme A

Question 4

What happens in Krebs cycle?

Answer 4

series of redox reactions produces:
- ATP by substrate-level phosphorylation
- Reduced coenzymes
- CO2 from decarboxylation

Question 5

What happens in ETC?

Answer 5

Electrons released from NADH & FAD undergo successive redox reactions.
Energy released is coupled to maintaining proton gradient or released as heat
Oxygen acts as final electron acceptor

Question 6

How is proton conc. gradient established during chemiosmosis in aerobic respiration?

Answer 6

Some energy released from ETC is coupled to active transport of H+ ions from mitochondrial matrix into intermembrane space.

Question 7

Role of oxygen in aerobic respiration

Answer 7

Final electron acceptor in electron transfer chain
(produces water as byproduct)

Question 8

How can lipids act as alternative respiratory substrate?

Answer 8

lipid - glycerol + fatty acids
1. Phosphorylation of glycerol - TP for glycolysis
2. fatty acids - acetate
a) acetate enters link reaction
b) H atoms produced for oxidative phosphorylation

Question 9

What happens during anaerobic in animals?

Answer 9

Only glycolysis continues NADH + pyruvate = Oxidised NAD (for further glycolysis) + lactate

Question 10

What happens to lactate produced in anaerobic respiration?

Answer 10

Transported to liver via bloodstream, where it is oxidised to pyruvate.
Can enter link reaction in liver cells or be converted to glycogen

Question 11

What happens during anaerobic respiration in some microorganisms?

Answer 11

Only glycolysis continues
Pyruvate is decarboxylated to form ethanal
Ethanal is reduced to ethanol using NADH to produce oxidised NAD for further glycolysis

Question 12

Contrast aerobic and anaerobic respiration

Answer 12

Aerobic:
- produces ATP by substrate-level phosphorylation
- produces much more ATP
- does not produce ethanol or lactate

Anaerobic:
- substrate-level phosphorylation only
- produces fewer ATP
- produces ethanol or lactate

Question 13

How to calculate rate of respiration using a respirometer?

Answer 13

Volume of O2 produced or CO2 consumes/ time x mass of sample
Volume= distance moved by coloured drop x (0.5 x capillary tube diameter) squared x Pi

Question 14

Summary equation for Link Reaction

Answer 14

Pyruvate + NAD + CoA -> acetyl CoA + NADH + CO2

Question 15

What is the Electron Transfer Chain (ETC)?

Answer 15

Series of carrier proteins embedded in membrane of cristae of mitochondria

Produces ATP through oxidative phosphorylation via chemiosmosis during aerobic respiration

Question 16

Name 2 types of molecules that can be used as alternative respiratory substrates

Answer 16

• (Amino acids from) proteins
• (Glycerol & Fatty acids from) lipids

Question 17

What is the ADVANTAGE of producing ethanol/ lactate during anaerobic respiration?

Answer 17

Converts NADH back into NAD so glycolysis can continue

Question 18

What is the DISADVANTAGE of producing ethanol during anaerobic respiration?

Answer 18

• Cells die when ethanol conc. is above 12%
• Ethanol dissolves cell membranes

Question 19

What is the DISADVANTAGE of producing lactate during anaerobic respiration?

Answer 19

Acidic, so decreases pH - results in muscle fatigue