ATP - Mark Scheme Answers (study Mind)

Question 1

Name the substance that muscles use as their immediate energy source.

Answer 1

ATP

Question 2

(ii) A person wishes to lose some body fat by exercising. What sort of exercise
would be most effective? Use the information in Figures 1 and 2 to explain
your answer.

Answer 2

Low intensity;At low intensity/below 40% mainly fat used / at high intensity/
above 40% mainly carbohydrate used;Long duration exercise;Percentage fat
used increases with time / percentage
carbohydrate used decreases with time;

Question 3

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

Answer 3

(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 4

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

Answer 4

Pyruvate

Question 5

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 5

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

Question 6

The Krebs cycle,, releases hydrogen ions.which 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 6

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

Question 7

Describe the roles of calcium ions and ATP in the contraction of a myofibril.

Answer 7

1. Calcium ions diffuse into myofibrils from (sarcoplasmic) reticulum;
2. (Calcium ions) cause movement of tropomyosin (on actin);
3. (This movement causes) exposure of the binding sites on the actin;
4. Myosin heads attach to binding sites on actin;
5. Hydrolysis of ATP (on myosin heads) causes myosin heads to bend;
6. (Bending) pulling actin molecules;
7. Attachment of a new ATP molecule to each myosin head causes myosin heads to detach (from actin sites).

Question 8

ATP is an energy source used in many cell processes. Give two ways in which ATP
is a suitable energy source for cells to use.

Answer 8

1. Releases relatively small amount of energy / little energy lost as heat;
2. Releases energy instantaneously;
3. Phosphorylates other compounds, making them more reactive;
4. Can be rapidly re-synthesised;
5. Is not lost from / does not leave cells.

Question 9

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

Answer 9

Released as heat

Question 10

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 10

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

Question 11

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

Answer 11

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

Question 12

Write a simple equation to show how ATP is synthesised from ADP.

Answer 12

ADP + Pi → ATP;

Question 13

Give two ways in which the properties of ATP make it a suitable source of energy in biological processes.

Answer 13

1. Energy released in small / suitable amounts;
2. Soluble;
3. Involves a single / simple reaction;

Question 14

Humans synthesise more than their body mass of ATP each day. Explain why it is
necessary for them to synthesise such a large amount of ATP.

Answer 14

1. ATP cannot be stored / is an immediate source of energy;
2. ATP only releases a small amount of energy at a time;

Question 15

In anaerobic respiration, what is the net yield of ATP molecules per molecule

of glucose?

Answer 15

2 molecules

Question 16

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

Answer 16

Cannot pass out of cell;
Quickly / easily broken down (hydrolysed) / broken

Question 17

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

Answer 17

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

Question 18

Describe the part played by the inner membrane of a mitochondrion in

producing ATP.

Answer 18

Electrons transferred down electron transport chain;

Provide energy to take protons / H+

into space between membranes;

Protons / H+ pass back, through membrane / into matrix / through ATPase;
Energy used to combine ADP and phosphate / to produce ATP;

Question 19

He suspended the mitochondria in an isotonic solution and added a suitable respiratory substrate together with ADP and phosphate. He bubbled oxygen through the preparation.

(i) Why was the solution in which the mitochondria were suspended isotonic?

Answer 19

Prevent damage to mitochondria caused by
water / osmosis / differences in water potential;

Question 20

Explain why the scientist did not use glucose as the respiratory substrate.

Answer 20

Glucose is used / broken down during glycolysis in cytoplasm / not in mitochondria

Glucose cannot cross mitochondrial membrane / does not enter mitochondria;

Question 21

Explain why the oxygen concentration would change during this investigation.

Answer 21

Terminal / final acceptor (in electron transport chain) / used to make water;

Question 22

Describe how an ATP molecule is formed from its component molecules.

Answer 22

1. components adenine,
   ribose/pentose, three phosphates;
2. Condensation (reaction);
3. ATP synthase;

Question 23

Name the two products of ATP hydrolysis.

Answer 23

ADP
Pi - inorganic phosphate

Question 24

(b) The new antibiotic is safe to use in humans because it does not inhibit the
ATP synthase found in human cells.
Suggest why human ATP synthase is not inhibited and bacterial synthase
is inhibited.

Answer 24

Human ATP synthase has a different tertiary structure to bacterial ATP synthase
Different active site shape to bacterial ATP

Question 25

ATP is an energy source used in many cell processes. Give two ways in
which ATP is a suitable energy source for cells to use.

Answer 25

1. Releases relatively small amount of energy / little energy lost as heat
2. Releases energy instantaneously
3. Phosphorylates other compounds, making them more reactive;
4. Can be rapidly re-synthesised;
5. Is not lost from / does not leave cells.

Question 26

Describe how ATP is resynthesised in cells.

Answer 26

1.From ADP and phosphate;

2. By ATP synthase;
3. During respiration/photosynthesis;

Question 27

Give two ways in which the hydrolysis of ATP is used in cells.

Answer 27

1. To provide energy for other reactions/named process;

Reject ‘produce’ energy

2. To add phosphate to other substances and make them more
   reactive/change their shape;