A-level Biology (7401/7402)

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(2)

(b) Apart from the yoghurt, it was important that all of the mice were given the same food each day.

Give two reasons why it was important that all of the mice were given the same food each day.

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(2)

(c) The scientists’ hypothesis was that adding the inhibitor of amylase to the food would lead to a lower blood glucose concentration.

Use your knowledge of digestion to suggest how the addition of the inhibitor could lead to a lower blood glucose concentration.

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(2)

(d) Give one reason why these results may not support the use of the inhibitor of amylase to treat diabetes in mice.

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(2)

(Total 8 marks)

Q13.The figure below shows the apparatus used for measuring the rate of oxygen consumption in aerobic respiration by seeds.

(a) For the first 10 minutes, the tap attached to tube A was left open and the syringe from tube B was removed.

Suggest three reasons why the apparatus was left for 10 minutes.

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(3)

(b) Suggest and explain why the chosen temperature was 20 °C for this experiment.

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(2)

After 10 minutes, the tap attached to tube A was closed and the syringe was attached to tube B. Every minute, the syringe plunger was moved until the levels in the U-tube were the same. The reading on the syringe volume scale was then recorded.

The results are shown in the table below.

	Time / minutes	Reading on syringe volume scale / cm³
	0	0.84
	1	0.81
	2	0.79
	3	0.76
	4	0.73
	5	0.70
	6	0.68
	7	0.66
	8	0.63
	9	0.62
	10	0.58

Explain what caused this.

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(Extra space) ................................................................................................

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(3)

(d) The mass of the seeds was 1.6 g. Use the information in the table above to calculate the rate of oxygen consumption in cm³ g^–1 hour^–1 by the seeds.

Show your working.

Rate = .................................................................................. cm³ g^–1 hour^–1

(2)

(Total 10 marks)

M1.(a) Oxygen production / concentration and time.

Accept: oxygen volume / concentration

Reject: oxygen uptake

Neutral: reference to carbon dioxide uptake

1

(b) 1. Intensity of light;

Accept: distance from light

2. Amount / number / mass / species of algae / photosynthesising cells;

3. Carbon dioxide (concentration / partial pressure);

4. Time.

2 max

Neutral: becomes more alkaline / less acidic

2. As (more) carbon dioxide removed (for photosynthesis).

(d) 1. Less absorption / (more) reflection (of these wavelengths of light);

Reject: no absorption or cannot absorb unless in context of green light.

Note: no green light absorbed or green light reflected = 2 marks.

2. (Light required) for light dependent (reaction) / photolysis

Accept: for excitation / removal of electrons (from chlorophyll)

3. (Represents) green light / colour of chlorophyll.

2 max

[7]

M2. (a) 1. Uses energy / ATP;

2. Against concentration gradient / low to high concentration;

3. Does not use channel proteins / only uses carrier proteins;

Assume “it” refers to active transport.

1. Facilitated diffusion is passive - neutral

2. Along / across concentration gradient - neutral

Accept up / down concentration gradient

Accept AT does not need concentration gradient.

2 max

(b) (i) To see the effect of the drug / effect not due to anything else in the tablet;

Neutral “to compare results”

1

(ii) Placebo / dummy drug / tablet without drug;

(Otherwise) treated the same;

No drug - neutral

Accept: Example e.g. tablet given at same time

2

Accept decreases from 1 - 4 hours

1

[6]

M3. (a) (i) Increase to 30 °C / 31 °C and then decreases / optimum or max rate at 30 °C / 31 °C;

Accept: peak at 30 °C / 31 °C

1

(ii) 1. Enzyme denatured / hydrogen bonds / bonds holding tertiary structure broken / tertiary structure changed;

2. Change in shape of active site (of enzymes);

3. Substrate / protein no longer fits / binds (into active site) / few or no ES complexes;

1. Reject: Peptide bonds broken

Denatures active site = 2 marks for mp 1 and 2

2. Q Only allow second point if active site is used correctly

Accept: active site no longer complementary

3. Accept: Substrate cannot bind to enzyme

3

(b) (i) Use buffer / test pH (at end / at intervals);

Accept a method of measuring pH.

Reject litmus.

1

(ii) (30 °C / 31 °C) Maximum rate / optimum temperature;

Accept other valid answers e.g. temp below
30 °C as enzyme not denatured.

1

(iii) Works best at pH 6 / at higher pH activity decreases;

Accept converse

Insufficient: pH 6 had largest clear area

1

[7]

M4.(a) All the fish / all the species / all the populations / all the organisms;

Must indicate all / every species.

Reject answers that suggest other fish / organisms might be present.

1

(b) (i) 1. Capture sample, mark and release;

2. Appropriate method of marking suggested / method of marking does not harm fish;

E.g. Cutting a fin / attaching a tag / paint / marker.

3. Take second sample and count marked organisms;

May be awarded from equation if not given here.

Accept any valid alternative to equation or answer expressed as a ratio.

3 max

(ii) One suitable reason;

Accept other valid answers, which must, however, relate to breeding / only works if population constant.

E.g. population increases / changes (between first and second sample)

Catches more food and gas exchange are neutral

2. Competition between species / interspecific competition is reduced;

Reject intraspecific

2

[7]

M5.(a) (i) 1. Sex;

2. Lifestyle;

Stress, smoking, diet etc are examples of lifestyle.

3. Body mass;

3. Allow weight for mark point 3.

4. Health;

Reject: height.

5. Ethnicity;

6. Genetic factors / family history;

2 max

(ii) 1. Large sample / number / 410 000;

Reject: random

2. Long time period / 8.5 / many years;

3. Different countries / more than one country;

2

(b) Correct answer of 209 / 209.1 = 2 marks;

Answer of 210 = one mark

Incorrect answer but multiplies by 8.5 = 1 mark;

Must relate to cancer not just to illness

1

(d) 1. Correlation does not mean causal relationship;

1. Reject casual for point 1.

Reference to 'due to other factors' on its own is not enough for a mark

2. Tea / coffee contains other substances / different amounts of caffeine / estimated intake (of tea / coffee);

3. No control group;

4. Only one type of cancer studied / further studies required / only one investigation / study / group;

(e) (i) 1. Treated the same;

2. Accept decaffeinated

2. No caffeine;

2. Reject placebo.

2

(ii) 1. Absorb different amounts;

Reject: Different body masses

2. Broken down by enzymes / digested;

3. Different blood volumes;

4. Differences in metabolism;

5. Caffeine from a different source;

1 max

(iii) 1. Less oxygen / glucose to (cancer) cells;

'Reduces cell division' on its own should not be credited.

2. Less carcinogens;

3. Reduces spread of cancer (cells);

1 max

[15]

M6.(a) EITHER

Answer either based on

1. Molecules move at slower speeds;

2 diffusion or

2. Decreases rate of diffusion;

4 enzymes.

OR

3. Molecules move at slower speed;

4. Fewer collisions between enzymes and substrates / fewer enzyme-substrate complexes formed;

Accept converse answers if clearly in context of “If it stayed at 30 C”.

2 max

(b) (i) 1. Allows comparison;

2. Different amounts of fungus added / fungus is different size at start;

2

(ii) Two marks for correct answer in range 1.7 : 1 to 1.3 : 1;;

Answer must be expressed this way round and must give the diameter of the fungus as 1.

One mark for unsimplified answer in range 29 : 19 to 27 : 21;

Calculations are based on tolerance limits for measurements of ± 1 mm. If the actual measurements are other than 28 and 20, marking guidelines should be adjusted accordingly.

2

2. No fungus growing here / must be enzyme here;

Accept any alternative wording clearly relating to colourless zone.

2

[8]

M7. (a) Ribulose bisphosphate / RuBP;

Accept Ribulose biphosphate or Ribulose diphosphate

Accept phonetic spellings

Accept any variation in upper or lower case for RuBP

1

(b) ATP and reduced NADP are produced in grana / thylakoids / present in A / both tubes;

Must be reduced NADP but accept any alternative which show hydrogen attached to NADP

Must be reduced NADP not reduced NAD

1

Accept ‘same as in (tube) C’, but not ‘same’ on its own

2. Light-dependent reaction does not occur / ATP and reduced NADP are not produced;

Accept converse for mark point 2

2

(d) 1. (Less) GP converted to TP;

GP = glycerate 3-phosphate

TP = triose phosphate but abbreviations are sufficient

2. (Less) TP converted to RuBP;

Accept GALP as TP

2

(e) 1. No / less ATP / ATP produced (during electron transport);

Must be reduced NADP but accept any alternative which shows hydrogen attached to NADP

2. No / less reduced NADP / reduced NADP produced (during electron transport)

2

[8]

M8. (a) 1. Add Benedict’s;

Hydrolyse with acid negates mp1

2. Heat;

Accept warm, but not an unqualified reference to water bath

3. Red / orange / yellow / green (shows reducing sugar present);

Accept brown

3

(b) (i) 1. Starch hydrolysed / broken down / glucose / maltose produced;

Neutral: Sugar produced

2. Lower water potential;

3. Water enters by osmosis;

3

(ii) Only 2 pHs studied / more pHs need to be tested;

Accept: different amylase may have a different optimum pH

1

[7]

M9.(a) 1. Fields of view randomly chosen;

2. Several fields of view;

3. All same species (of animal / hamster);

Reject general statements related to sample size. All mark points relate directly to information provided in Resource A.

Accept ‘all (Mesocricetus) auratus’.

4. Same muscle / organ used / only diaphragm used;

5. Used at least 8 (animals) in each (age) group.

4 max

(b) (i) 15

Correct answer = 2 marks.

Allow 1 mark for showing

69 ÷ 4.6

OR

answer of 10 / 10.1 (correct calculation using fast in error.)

2

(ii) 1. (Calculation) used mean (number of capillaries);

2. Variation in number of capillaries per fibre.

Note: maximum of 1 mark for this question.

Ignore reference to an anomaly or calculation errors.

1 max

(ii) 1. (Suggests) significant (difference) between young and adult;

MP1, MP2, MP4 and MP5 can include use of figures but check figures are used correctly.

2. (Suggests) not significant (difference) between adult and old;

Statements related to ‘results being significant / not significant’ do not meet the marking points. It is the difference that is significant or not. However, only penalise this error once.

3. For slow and fast fibres;

This MP can be given in the context of either MP1 or MP2 but only allow once. As well as this context there must be a reference to ‘both’ types of fibre.

4. (Suggests) significant (difference) between young and old for fast (fibres)

OR
(Suggests) not significant (difference) between young and old for slow (fibres);

All aspects of either approach required to gain credit.

5. (Suggests) significant (difference) where means ± SD do not overlap

OR
(Suggests) not significant (difference) where means ± SD overlap;

All aspects of either approach required to gain credit.

6. Stats test is required (to establish whether significant or not).

4 max

[12]

M10.(a) Open / use tap / add water from reservoir;

1

(b) 1. Seal joints / ensure airtight / ensure watertight;

Answer must refer to precautions when setting up the apparatus

Ignore: references to keeping other factors constant

2. Cut shoot under water;

3. Cut shoot at a slant;

4. Dry off leaves;

5. Insert into apparatus under water;

6. Ensure no air bubbles are present;

7. Shut tap;

8. Note where bubble is at start / move bubble to the start position;

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