CH12 Respiration

Question 1

4 main stages in aerobic respiration and their locations

Answer 1

Glycolysis - Cytoplasm
Link reaction - Mitochondrial matrix
Krebs cycle - Mitochondrial matrix
Oxidative phosphorylation - ETC - membrane of cristae

Question 2

Stages of glycolysis

Answer 2

Glucose phosphorylated to glucose phosphate by 2ATP
Glucose phosphate splits into 2 triose phosphate
2 TP is oxidised to 2 pyruvate
Net gain of 2 reduced NAD and 2 ATP per glucose

Question 3

How does pyruvate from glycolysis enter mitochondria

Answer 3

Active transport

Question 4

What happens in link reaction

Answer 4

1. Oxidation of pyruvate to acetate
   per molecule of pyruvate - net gain of 1 CO2 and 2H atoms (used to reduce NAD)
2. Acetate combines with coenzyme A to form acetylcoenzyme A

Question 5

What happens in Krebs cycle

Answer 5

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

Question 6

What is the electron transfer chain (ETC)

Answer 6

Series of carrier proteins embedded in membrane of the cristae of mitochondria
Produces ATP through oxidative phosphorylation via chemiosmosis during aerobic respiration

Question 7

What happens in the ETC

Answer 7

Electrons released from reduced NAD and FAD undergo successive redox reactions
The energy released is coupled to maintaining a proton gradient or released as heat
Oxygen is the final electron acceptor

Question 8

How is a proton concentration established

Answer 8

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

Question 9

How does chemiosmosis produce ATP

Answer 9

H+ ions move down their concentration gradient from the intermembrane space into the mitochondrial matrix via the channel protein ATP synthase

Question 10

State the role of oxygen in aerobic respiration

Answer 10

Final electron acceptor in ETC

Produces water as a byproduct

Question 11

Benefit of ETC rather than single reaction

Answer 11

Energy released gradually

Less energy released as heat

Question 12

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

Answer 12

Proteins - AA

Lipids - glycerol and fatty acids

Question 13

How can lipids act as alternative respiratory substrate

Answer 13

Lipid –> glycerol + fatty acids
1. Phosphorylation of glycerol - TP for glycolysis
2. Fatty acid - acetate
a] acetate enters link reaction
b] H atoms produced for oxidative phosphorylation

Question 14

How can AA act as an alternative respiratory substrate

Answer 14

Deamination produces:

1. 3C compounds - pyruvate for link reaction
2. 4C / 5C compounds - intermediates for Krebs cycle

Question 15

Stages in respiration that produce ATP by substrate level phosphorylation

Answer 15

Glycolysis (anaerobic)
Krebs cycle (aerobic)

Question 16

What happens during anaerobic respiration in animals

Answer 16

Only glycolysis continues

reduced NAD + pyruvate –> oxidised NAD (for further glycolysis) + lactate

Question 17

What happens to lactate produced in anaerobic respiration

Answer 17

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

Question 18

What happens during anaerobic respiration in some microorganisms

Answer 18

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

Question 19

Advantage of producing ethanol / lactate during anaerobic respiration

Answer 19

Converts reduced NAD back into NAD so glycolysis can continue

Question 20

Disadvantage of producing ethanol

Answer 20

Cells die when ethanol conc is above 12%

Ethanol dissolves cell membranes

Question 21

Disadvantage of producing lactate

Answer 21

Acidic, decreases pH

Results in muscle fatigue

Question 22

Compare aerobic and anaerobic respiration

Answer 22

Both involve glycolysis
Both require NAD
Both produce ATP

Question 23

Contrast aerobic and anaerobic respiration

Answer 23

Aerobic produces ATP by substrate-level phosphorylation and oxidative phosphorylation but anaerobic only produces ATP by substrate-level phosphorylation
Aerobic produces more ATP than anaerobic
Aerobic does not produce ethanol or lactate but anaerobic does

Question 24

How to investigate effect of variable on rate of respiration of single-celled organism

Answer 24

Use respirometer

Use a dye as the terminal electron acceptor for the ETC

Question 25

Purpose of sodium hydroxide solution in respirometer

Answer 25

Absorbs CO2 so there is a net decrease in pressure as O2 is consumed