Respiration

Question 1

Name the 4 main stages in aerobic respiration and where they occur

Answer 1

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

Question 2

Outline the stages of glycolysis

Answer 2

1. Glucose is phosphorylated to glucose phosphate by 2x ATP
2. Phosphorylated glucose splits into 2x triose phosphate
3. 2x triose phosphate is oxidised to 2x pyruvate

Question 3

How does pyruvate from glycolysis enter the mitochondria?

Answer 3

Active transport

Question 4

What happens during the link reaction?

Answer 4

1. Oxidation of pyruvate to acetate

2. Acetate combines with coenzyme A to form acetylcoenzyme A

Question 5

What is the equation for the link reaction?

Answer 5

Pyruvate + NAD + CoA = acetyl CoA + reduced NAD + CO2

Question 6

What happens in the krebs cycle?

Answer 6

A series of redox reactions produces:

ATP by substrate level phosphorylation

Reduced coenzymes

CO2 from decarboxylation

Question 7

What is the electron transfer chain?

Answer 7

A series of carrier proteins embedded in the membrane of the cristae of mitochondria

Produces ATP through oxidative phosphorylation via chemiosmosis during aerobic respiration

Question 8

What happens in the electron transport chain?

Answer 8

Electrons released from reduced NAD and FAD undergo successive redox reactions

The energy released is coupled to maintain the proton gradient or released as heat

Oxygen acts as a final electron acceptor

Question 9

How is a proton concentration gradient established during chemiosmosis in aerobic respiration?

Answer 9

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

Question 10

How does chemiosmosis produce ATP during aerobic respiration?

Answer 10

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

Question 11

State the role of oxygen in aerobic respiration

Answer 11

Final electron acceptor in electron transport chain

Question 12

What is the benefit of an electron transfer chain rather than a single reaction?

Answer 12

Energy is released gradually

Less energy is released as heat

Question 13

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

Answer 13

Amino acids from proteins

Glycerol and fatty acids from lipids

Question 14

How can lipids be used as an alternative respiratory substrate?

Answer 14

1. Phosphorylation of glycerol = triose phosphate for glycolysis
2. Fatty acid = acetate

Acetate enters the link reaction
H atoms produced for oxidative phosphorylation

Question 15

How can amino acids act as an alternative respiratory substrate?

Answer 15

1. 3C compounds= pyruvate for link reaction

2. 4C/5C compounds= intermediates in the Krebs cycle

Question 16

Name the stages in respiration that produce ATP by substrate level phosphorylation

Answer 16

Glycolysis (anaerobic)
Krebs cycle (aerobic)

Question 17

What happens during anaerobic respiration in animals?

Answer 17

Only glycolysis continues

Reduced NAD + pyruvate = oxidised NAD + lactate

Question 18

What happens to lactate produced in anaerobic respiration?

Answer 18

Transported to the liver via the bloodstream where it is oxidised to pyruvate

Can enter the link reaction in liver cells or be converted to glycogen

Question 19

What happens during anaerobic respiration in some microorganisms e.g yeast and some plant cells?

Answer 19

Only glycolysis continues

Pyruvate is decarboxylated to form ethanal

Ethanal is reduced to ethanol using reduced NAD to produce oxidised NAD for further glycolysis

Question 20

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

Answer 20

Converts reduced NAD back into NAD so glycolysis can continue

Question 21

What is the disadvantage of producing ethanol during anaerobic respiration?

Answer 21

Cells die when ethanol concentration is above 12%

Ethanol dissolves cell membranes

Question 22

What is the disadvantage of producing lactate during anaerobic respiration?

Answer 22

Acidic, so decreases pH

Results in muscle fatigue

Question 23

Compare aerobic and anaerobic respiration

Answer 23

Both involve glycolysis
Both require NAD
Both produce ATP

Question 24

Contrast aerobic and anaerobic respiration

Answer 24

Aerobic:

Produces ATP by substrate level phosphorylation and oxidative phosphorylation

Produces much more ATP

Does not produce ethanol or lactate

Anaerobic:

Substrate level phosphorylation only

Produces fewer ATP

Produces ethanol or lactate