Topic 5.5 Anaerobic respiration

Question 1

What is anaerobic respiration?

Answer 1

Partial breakdown of hexose sugars (glucose) in oxygen-deprived conditions to produce a limited ATP yield.

Question 2

What happens during anaerobic respiration in animals?

Answer 2

Only glycolysis continues

reduced NAD + pyruvate

–>

oxidised NAD (for further glycolysis) + lactate

Question 3

Explain how lactate is produced in anaerobic respiration

Answer 3

Pyruvate acts as a hydrogen acceptor –(reduced NAD -> oxidised NAD)–> lactate

Question 4

What happens to the lactate produced in anaerobic respiration?

Answer 4

Transported to the liver in bloodstream. Oxidised to pyruvate by lactate dehydrogenase. Involves conversion of NAD to reduced NAD.

Enters link reaction in liver cells or is converted to glycogen.

Question 5

How does lactate affect muscle contraction in mammels?

Answer 5

Acidic, so decreases pH.

Results in muscle fatigue.

Question 6

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

Answer 6

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 7

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

Answer 7

Converts NADH back into NAD so glycolysis can continue.

Question 8

What is the disadvantage of producing ethanol during respiration?

Answer 8

Dissolves cell membranes so cells die when concentration is above 12%

Question 9

Compare the ATP yields per molecule of hexose sugar from aerobic and anaerobic respiration

Answer 9

Aerobic ≈ 38 in ideal conditions

Anaerobic ≈ 2 from glycolysis

Question 10

Explain the principle behind using a respirometer

Answer 10

Preasure changes in the boiling point tube due to CO₂ production (anaerobic experiments) or O₂ consumption (aerobic experiments) cause a drop of coloured liquid to move.

Question 11

What is the purpose of NaOH solution in a respirometer set up to measure the rate of aerobic respiration?

Answer 11

Absorbs CO₂ so that there is a net decrease in preassure as O₂ is consumed.

Question 12

How could a student calculate the rate of repiration using a respirometer?

Answer 12

• Volume of O₂ produced or CO₂ consumed / time x mass of sample
• Volume = distance moved by coloured drop x (0.5 x capillary tube diameter)² x π.