Respiration Exam Questions

Question 1

Explain why the incomplete breakdown of glucose in anaerobic respiration produces less ATP than aerobic respiration.
(2 MARKS)

Answer 1

1 - some ATP used to actively transport pyruvate into the mitochondrion
2 - some ATP used to actively transport H(+) from NADH ,
formed in glycolysis / into the mitochondrion
3 - some energy released in ETC , is not used to transport H+ across inner membrane
4 - not all the H+ movement back across membrane , is used to generate ATP
5 - not all the, NADH , is used to feed into the ETC

Question 2

Explain why the incomplete breakdown of glucose in anaerobic respiration produces less ATP than aerobic respiration.
(5 MARKS)

Answer 2

in anaerobic respiration
1 - glycolysis occurs
2 - produces 2 molecules of ATP (net)
3 - only substrate level phosphorylation occurs
4 - oxygen not available as final electron acceptor
5 - pyruvate / ethanal used to regenerate NAD for glycolysis to continue ;
6 - Krebs cycle and electron transport chain / chemiosmosis /
oxidative phosphorylation ,do not occur (ONLY occurs in aerobic)

Question 3

Certain parasites live in the blood of mammals. Suggest why, even though blood carries oxygen, these parasites are adapted to respire anaerobically
(2 MARKS)

Answer 3

1 - idea that parasites have little access to oxygen ;
2 - inaccessible because little oxygen dissolved in plasma /
oxygen not very soluble in plasma
3 - inaccessible because idea that oxygen is , combined with haemoglobin contained in red blood cells ;
4 - idea that haemoglobin has greater affinity for oxygen
than parasite pigment

Question 4

The anaerobic respiration pathway in animal cells can be reversed, but the anaerobic respiration pathway in yeast cells cannot be reversed. Explain why, using your knowledge of the differences between the two pathways.
(4 MARKS)

Answer 4

in animals
1 - pyruvate is reduced to lactate / lactic acid ;
2 - can be reversed as no atoms are lost
3 - lactate dehydrogenase available to reverse the reaction
in yeast
1 - pyruvate converted to ethanol and carbon dioxide
2 - cannot be reversed as carbon dioxide is lost
3 - decarboxylase enzyme cannot reverse the reaction

Question 5

Outline the process of glycolysis

4 MARKS

Answer 5

1 - phosphorylation of glucose ;
2 - so forming hexose (1,6) bisphosphate ;
3 - then splitting into 2 triose phosphates
4 - for the formation of pyruvate, the formation of reduced NAD
5 - pyruvate produced from triose phosphate
6 - total production 4 ATP, net production of 2 ATP

Question 6

Herbicides (weedkillers) interfere with electron transport by accepting electrons.
Suggest how this causes plants to die.
(3 MARKS)

Answer 6

1 - no photophosphorylation
2 - no ATP produced
3 - no reduced NADP produced
4 - no Calvin cycle / no light-independent stage
5 - no GP to TP / no TP to RuBP
6 - no fixation of carbon dioxide

Question 7

State what is meant by the term respiratory substrate.

1 MARK

Answer 7

1 - a biological molecule that can be broken down in respiration to release energy

Question 8

Describe how the apparatus shown in the diagram could be used to determine the rate of respiration of the bread mould, Mucor. (a diagram of a respirometer)
(4 MARKS)

Answer 8

1 - to potassium hydroxide/soda lime;
2 - to equilibration/use syringe to set manometer fluid (level);
3 -leave for suitable length of time (minimum 20 minutes) and measure distance moved by fluid
4 - repeats and calculate mean
5 - calculate the volume of oxygen taken up per minute;
6 - ref to the set-up of control tube (e.g. same mass of beads as of fungus) or (same volume of inert substance as substance A)
7 - detail of how to calculate the volume of oxygen (by multiplying
distance moved by fluid in the capillary by 2πr)

Question 9

Explain the following terms:

a) decarboxylation
b) dehydrogenation

Answer 9

a) removal of carboxyl group

b) removal of hydrogen

Question 10

State where the reduced NAD and reduced FAD molecules are reoxidised and describe what happens to the hydrogen atoms.
(4 MARKS)

Answer 10

1 - cristae
2 - ref to (NADH) dehydrogenase
3 - hydrogen split into protons and electrons
4 - ref to, electron carriers/cytochromes
5 - energy released from electrons
6 - ref to protons pumped across the membrane
7 - protons accumulate in intermembrane space
8 - proton gradient/pH gradient/H+ gradient
9 - protons pass through ATP synthetase
10 - oxygen final electron acceptor
11 - formation of water

Question 11

The liver is responsible for producing enzymes which detoxify alcohol by breaking it down into smaller units. This breakdown by enzymes uses NAD. This means that other reactions that use NAD are less likely to take place. The build up of fats in the liver is one of the first signs of liver damage due to excessive alcohol
intake.
Explain why the build up of fats occurs in the liver of an individual who consumes large amounts of alcohol.
(3 MARKS)

Answer 11

1 - fats/fatty acids, not respired
2 - β-oxidation of fatty acids requires NAD
3 - NAD used in breakdown of alcohol
4 - NAD is in short supply
5 - fats formed from fatty acids plus glycerol

Question 12

Explain why carbon dioxide is produced when mitochondria are incubated with
pyruvate but not when incubated with glucose.
(3 MARKS)

Answer 12

1 - pyruvate is end product of glycolysis
2 - pyruvate can enter mitochondria
3 - carbon dioxide produced in the Krebs cycle and link reaction by decarboxylation
glucose cannot enter the mitochondria

Question 13

Explain why, in the presence of cyanide, ethanol production can still occur.
(3 MARKS)

Answer 13

1 - pyruvate is converted to ethanal in cytoplasm
2 - ethanal is converted to ethanol does not involve, cytochromoes / ETC / oxidative phosphorylation
3 - enzymes in cytoplasm not inhibited by cyanide

Question 14

State the number of ATP molecules that are made directly per ‘turn’ of the cycle.
(1 MARK)

Answer 14

1

Question 15

State the number of reduced NAD and reduced FAD molecules that are formed in the Krebs cycle from one molecule of acetyl CoA.
(2 MARKS)

Answer 15

3 reduced NAD

1 reduced FAD

Question 16

Many seeds contain food stores, including starch, proteins and lipids. A fully developed
seed of H. annuus contains between 40% and 50% of unsaturated fatty acids, including
oleic acid and linoleic acid. These fatty acids can be used as respiratory substrates for
the production of ATP.
Explain why seeds need ATP.
(2 MARKS)

Answer 16

1 - source of energy

2 - for germination/for growth/protein synthesis/spindle formation/organelle replication

Question 17

Explain the advantages of storing lipid for use as a respiratory substrate in
seeds.
(2 MARKS)

Answer 17

1 - higher energy density
compared to, glucose/protein;
2 - higher proportion of, hydrogen atoms/carbon -hydrogen bonds
3 - advantage for dispersal/named advantage;

Question 18

After chasing prey, a cheetah breathes rapidly (pants) for half an hour before it can run
again.
Explain why panting is necessary.
(4 MARKS)

Answer 18

heat loss
1 - body/blood, temperature rises
2 - may denature, enzymes/proteins;
3 - panting cools body;
4 - evaporative cooling;

fate of lactate
5 - high lactate concentration needs to be reduced;
6 - due to anaerobic respiration;
7 - panting provides extra oxygen/oxygen debt;
8 - lactate oxidized to pyruvate

respiratory gases
9 - myoglobin would be re-oxygenated;
10 - haemoglobin would be re-oxygenated;
11 - ATP/CP, resynthesised in muscle tissue;
12 - removal of extra carbon dioxide

Question 19

Hummingbirds are very small. Typically their mass is between 3 and 5 g. They are able to hover at a fixed point in the air by beating their wings very rapidly. The rufous
hummingbird, Selasphorus rufus, is a migratory species. It breeds in Canada and
Alaska in the summer, migrates south to Mexico in the autumn and returns to high latitudes in spring after completing its annual moult (loss of feathers, which are then re-grown).
Suggest why the rufous hummingbird has a very high requirement for energy.
(4 MARKS)

Answer 19

1 - for flying/hovering/beating wings;
2 - muscle activity, of energy demand of flight
3 - small size qualified; e.g. increases heat loss/
ref. large surface area to volume ratio
4 - homeothermic qualified;
5 - migration qualified;
6 - feather growth qualified; mitosis/protein synthesis

Question 20

Describe the structure of ATP.

4 MARKS

Answer 20

1 - nitrogenous base / purine, adenine 
2 - pentose sugar ; ribose 
3 - three, phosphate groups 
4 - phosphorylation nucleotide 
5 - AN adenosine as an alternative to adenine plus ribose

Question 21

NAD, FAD and NADP are important molecules in plant cells. Describe, in detail, the
role of these molecules within a palisade mesophyll cell.
(7 MARKS)

Answer 21

1 - NAD / FAD, involved in respiration
2 - associated with, dehydrogenase enzymes
3 - 2 molecules of NAD reduced in glycolysis ;
4 - link reaction producing 1 molecule of reduced NAD
5 - Krebs cycle produces 3 reduced NAD per turn of cycle
6 - detail of any one step in respiration where reduced NAD is produced
7 - Krebs cycle produces 1 reduced FAD per turn of cycle
8 - transfers hydrogen to, inner mitochondrial membrane
9 - mitochondrial shuttle bringing NAD reduced from glycolysis into matrix
10 - NADP involved in photosynthesis
11 - produced in non-cyclic photophosphorylation
12 - hydrogen comes from, water / photolysis
13 - (used in) Calvin cycle / light independent stage
14 - Glycerate 3-phosphate to triose phosphate
15 - NADP involved in transporting hydrogen from grana to stroma
16 - hydrogen split into electrons and protons at ETC

Question 22

Explain why, under aerobic conditions, lipids have a greater energy value per unit
mass than carbohydrates or proteins.
(2 MARKS)

Answer 22

1 - oxidative phosphorylation and ATP production
2 - needs supply of hydrogen
3 - to form reduced, NAD / FAD
4 - lipids have more, hydrogen / hydrogen – carbon bonds
5 - more acetyl Co enzyme A generated / more ‘turns’ of Krebs cycle

Question 23

Many chemicals will ‘uncouple’ oxidation from phosphorylation. In this situation, the energy released by oxidation of food materials is converted into heat instead of being used to form ATP. One such compound is dinitrophenol, which was used in munition factories for the manufacture of explosives during the First World War. People working in these factories were exposed to high levels of dinitrophenol.
Suggest and explain why people working in munitions factories during the First World
War became very thin regardless of how much they ate.
(3 MARKS)

Answer 23

1 - dinitrophenol in body
2 - ETC still functioning
3 - less ATP formed in respiration
4 - food not enough to meet metabolic demands of body
5 - body tissues had to respire
6 - heat production increasing metabolic rate

Question 24

When plants are grown in glasshouses during autumn and winter, when the natural light intensities are low, it is important that temperatures are kept relatively low.
With reference to respiration and photosynthesis, explain why it is essential to do
this.
(3 MARKS)

Answer 24

1 - light intensity limiting factor
2 - low rate photosynthesis
3 - rate respiration increases at higher temperatures
4 - rate respiration exceeds rate of photosynthesis
5 - net primary productivity is lower