respiration

Question 1

1aGas exchange in fish takes place in gills. Explain how two features of gills gas exchange.

Answer 1

Filaments / lamellae provide large surface area;
Thin / flattened epithelium / one / two cell layers so short diffusion pathway (between water and blood);
Countercurrent / blood flow maintains concentration / diffusion gradient;

Question 2

1iii The zoologist measured oxygen uptake per gram of body mass. Explain why he measured oxygen uptake per gram of body mass.

Answer 2

Enables comparison;
As animals differ in size / mas

Question 3

2a (a)
The biochemical pathway of aerobic respiration involves a number of different steps.
Name one step in which carbon dioxide is produced.

Answer 3

Krebs cycle / link reaction

Question 4

2b In an investigation, scientists transferred slices of apple from air to anaerobic conditions in pure nitrogen gas. They measured the rate of carbon dioxide production.
(b) The scientists kept the temperature constant throughout the investigation. Explain how a decrease in temperature would affect the rate of carbon dioxide production.

Answer 4

(Respiratory reactions controlled by) enzymes;
Rate decreases as less kinetic energy / fewer collisions (between substrate and active site) fewer E-S complexes formed;

Question 5

2d The rate of carbon dioxide production was higher when the apple slices were in nitrogen than when they were in the air. Explain why.

Answer 5

Respiring anaerobically;
(Anaerobic respiration / respiration with nitrogen) less efficient / produces less ATP;
More anaerobic respiration / more glucose / substrate must be respired to produce same amount of ATP (so more carbon dioxide produced);
/ mass;

Question 5

3d (d) People with mitochondrial disease have mitochondria that do not function properly.
Some people with mitochondrial disease can only exercise for a short time. Explain why a person with mitochondrial disease can only exercise for a short time.

Answer 5

(Mitochondria) use aerobic respiration;
Mitochondria produce ATP / release energy required for muscles (to contract);

Question 6

4c Explain why oxygen is needed for the production of ATP on the cristae of the mitochondrion.

Answer 6

ATP formed as electrons pass along transport chain;
oxygen is terminal electron acceptor / accepts electrons from electron
transport chain / electrons cannot be passed along electron transport
forms H O / accepts H 2

Question 7

5
The kangaroo rat is a small desert mammal. It takes in very little water in its food drinks. Its core body temperature is 38 °C.
The kangaroo rat takes in some water by feeding and drinking. Describe another which the kangaroo rat could obtain water.

Answer 7

etabolic water / from respiration;
erobic / use of oxygen;

Question 8

6a iii (iii)
In the presence of oxygen, respiration yields more ATP per molecule it does in the absence of oxygen. Explain why.

Answer 8

Oxygen as terminal hydrogen / electron acceptor allowing operation of electron transport chain / oxidative phosphorylation;
Fate of pyruvate;
Significance of ATP formed in glycolysis;

Question 9

7a describe and explain the link between oxygen concentration, rate of respiration and rate of uptake of potassium ions.

Answer 9

greater rate of oxygen consumption / leads to greater rate of respiration and greater rate of uptake;

oxygen required for respiration;
respiration produces ATP / releases energy;
(ignore ref to producing or making energy)
potassium ions taken up by active transport / against concentration gradient;

Question 10

8a iii Explain why converting pyruvate to ethanol is important in allowing the continued production of ATP in anaerobic respiration.

Answer 10

allows NAD to be recycled / re-formed;
so that glycolysis / described / candidates answer to (i) can proceed / so that (more) glucose can be converted to pyruvate / so that process X can continue;

Question 11

8b I (b) Give two ways in which anaerobic respiration of glucose in yeast is
(i) similar to anaerobic respiration of glucose in a muscle cell;

Answer 11

ATP formed / used;
pyruvate formed / reduced;
NAD / reduced NAD;
glycolysis involved / two stage process;

Question 12

8bii Give two ways in which anaerobic respiration of glucose in yeast is
(ii) different from anaerobic respiration of glucose in a muscle cell.

Answer 12

ethanol / alcohol formed by yeast, lactate (allow lactic acid) by muscle cell; CO released by yeast but not by muscle cell;

Question 13

ci Some students investigated the effect of temperature on the rate of anaerobic respiration in yeast. The apparatus they used is shown in the diagram. The yeast suspension was mixed with glucose solution and the volume of gas collected in five minutes was recorded.
Each student repeated the experiment and the results were pooled. Explain the advantages of collecting a large number of results.

Answer 13

allows anomalies to be identified / increases reliability (of means / averages / results);
allows use of statistical test;

Question 14

9aii Give two advantages of ATP as an energy-storage molecule within a
cell

Answer 14

Cannot pass out of cell;
Quickly / easily broken down (hydrolysed) / broken
down in a on-step reaction / immediate source of energy; Stores / releases small amounts of energy;

Question 15

9b Describe how NAD is regenerated in anaerobic respiration in yeast cells.

Answer 15

Formed when reduced NAD used to reduce / donate H ions to pyruvate / convert pyruvate to ethanol;

Question 16

11d Apart from respiration, give three uses of ATP in a liver cell.

Answer 16

Source of energy / of phosphate;
Active transport;
Phagocytosis / endo- / exocytosis / pinocytosis; Bile production;
Cell division / mitosis;

Question 17

11e Human skeletal muscle can respire both aerobically and anaerobically. Describe what happens to pyruvate in anaerobic conditions and explain why anaerobic respiration is advantageous to human skeletal muscle.

Answer 17

Forms lactate; [extras – C H OH / CO – CANCEL]
Use of reduced NAD / NADH;
Regenerates NAD;

Question 18

12(a) What is meant by the term partial pressure?

Answer 18

(a) It is a measure of the concentration of a gas

Question 19

11g The change to the dissociation curve is one of a number of ways in which the total oxygen supplied to muscles is increased during exercise. Give two other ways in which the total oxygen supplied to muscles during exercise is increased.

Answer 19

increased depth / rate / pulmonary ventilation;
increase stroke volume / heart rate / Q increases blood flow rate; arterioles [Accept artery] supplying the muscles
dilate / vasodilation / greater proportion of blood flow to the muscles

Question 20

13a Pyruvate is formed in the breakdown of glucose during respiration. When there is sufficient oxygen, this pyruvate is fully broken down. Name two substances formed from the pyruvate.

Answer 20

CO , water, ATP, reduced NAD / FAD;

Question 21

13bi (b) (i)
If there is a shortage of oxygen in muscle cells during exercise, some pyruvate is converted into lactate. Explain why muscles become fatigued when insufficient oxygen is available.

Answer 21

build up / increased concentration of lactate lowers pH

Question 22

(ii) Some of the lactate is oxidised to pyruvate by muscles when they are well-supplied with oxygen. Suggest an advantage of the lactate being oxidised in the muscles.

Answer 22

lactate / pyruvate is an energy source;
muscles have increased / immediate energy or ATP supply; (accept lactate replenishes glycogen or glucose)
restores pH levels;

Question 23

An investigation was carried out into the production of ATP by mitochondria. ADP, phosphate, excess substrate and oxygen were added to a suspension of isolated mitochondria.

Suggest the substrate used for this investigation.

Answer 23

pyruvate / succinate / any suitable Krebs cycle substrate;

Question 24

15a n which part of the mitochondrion does the Krebs cycle take place?

Answer 24

matrix;

Question 25

15b (b) Name two substances for which there would be net movement into the mitochondrion.

Answer 25

pyruvate; ADP; P / inorganic phosphate; reduced NAD; oxygen

Question 26

c -the mitochondria in muscles contain many cristae. Explain the advantage of this

Answer 26

arger surface area for electron carrier system / oxidative phosphorylation; provide ATP / energy for contraction;

Question 26

d ii During a dive, blood flow to the diaphragm muscles of a seal is reduced. Suggest the advantage to the seal of maintaining some blood supply to the diaphragm muscles during a dive.

Answer 26

supplies oxygen / glucose or removal of carbon dioxide / lactate; so cells can respire when not contracting / breathing;

Question 27

17b Pea plants respire aerobically, producing ATP which can be used for amino acid synthesis. Describe the role of oxygen in aerobic respiration.

Answer 27

final acceptor for hydrogen: to form water;

Question 28

c he bacteria respire anaerobically. This produces hydrogen and ATP used in nitrogen fixation. The hydrogen comes from reduced NAD. Explain how the regeneration of NAD in this way allows ATP production to continue.

Answer 28

glycolysis can continue; NAD can accept more hydrogen;

Question 29

18b ther substances are produced in the Krebs cycle in addition to the carbon compounds shown in the diagram. Name three of these other products.

Answer 29

reduced NAD / NADH / NADH ; 2 reduced FAD / FADH / FADH ; 2 ATP;

Question 30

20 ii In which part of a chloroplast does the light-independent reaction occur?

Answer 30

stroma;

Question 31

20 iii Which process is the source of the ATP used in the conversion of glycerate 3-phosphate (GP) to triose phosphate?

Answer 31

light-dependent reaction / (photo)phosphorylation;

Question 32

21 (a) Mitochondria in muscle cells have more cristae than mitochondria in skin cells. Explain the advantage of mitochondria in muscle cells having more cristae.

Answer 32

more cristae / larger surface area) for electron transport chain / more enzymes for ATP production / oxidative phosphorylation; muscle cells use more ATP (than skin cells)(not just more respiration

Question 33

Substance X enters the mitochondrion from the cytoplasm. Each molecule has three carbon atoms. Name substance X

Answer 33

(b) (i) pyruvate;

Question 34

ii In the link reaction substance X is converted to a substance with molecules effectively containing only two carbon atoms. Describe what happens in this process.

Answer 34

carbon dioxide formed / decarboxylation; hydrogen released / reduced NAD formed; acetyl coenzyme A produced;

Question 35

21c The Krebs cycle, which takes place in the matrix, releases hydrogen ions. These hydrogen ions provide a source of energy for the synthesis of ATP, using coenzymes and carrier proteins in the inner membrane of the mitochondrion. Describe the roles of the coenzymes and carrier proteins in the synthesis of ATP.

Answer 35

(c) NAD / FAD reduced / hydrogen attached to NAD / FAD; energy made available as electrons passed on; energy used to synthesise ATP from ADP and phosphate / using ATPase; H H / protons passed into intermembrane space; / protons flow back through stalked particles / enzyme;

Question 36

23 ii When glucose is respired what happens to the energy which is not incorporated into ATP?

Answer 36

released as heat;

Question 37

23bi When one mole of glucose is respired anaerobically, only 2 moles of ATP are produced. Explain why less energy is released in anaerobic respiration.

Answer 37

glucose only partly broken down / only broken down to lactate;

Question 38

23bii At the end of a sprint race, a runner continues to breathe rapidly for some time. Explain the advantage of this.

Answer 38

lactate / lactic acid has built up / been produced; oxygen used to break down lactate / convert it back to pyruvate / glucose / glycogen;

Question 39

25b (b) Without oxygen, less ATP is produced by respiration. Explain why.

Answer 39

Oxygen is the termina/ acceptor; (No) electron transfer chain / proton transfer / no oxidative phosphorylation; Which produces most of the ATP (in aerobic respiration); Only glycolysis takes place; Pyruvate used to make lactate; Only produces (net) 2 ATP (per molecule of glucose);

Question 40

Glycolysis Electron transfer chain where

Answer 40

Cytoplasm (of cell); In membranes/cristae (of mitochondria);