Cambridge A Level Biology 9700 — 2020 Feb/March Paper 1 · Variant 2

Question 1

1 The diagram shows an eyepiece graticule and cell viewed through a microscope. When the eyepiece graticule was calibrated at this magnification, the whole length of the graticule shown covered 12 divisions of a stage micrometer scale. There were 100 divisions in 10 mm of the stage micrometer. 0 10 20 30 40 50 60 70 80 90 100 What is the actual length of the cell? A 2.5 µm B 3.6 µm C 360 µm D 3 mm

Accepted Answer

C

Question 2

2 Which cell structures can form vesicles?

cell structure

cell surface
membrane

endoplasmic
reticulum

Golgi body

key
/ = can form vesicles

X = cannot form vesicles

Accepted Answer

A

Question 3

3 The diagram shows three circles, 1, 3 and 5, representing chloroplasts, mitochondria and typical prokaryotes. circle 3 circle 1 circle 5 2 4 Which row correctly identifies the three circles and some of the structures that are shared between them? circle 1 2 circle 3 4 circle 5 A chloroplasts circular DNA mitochondria 80S ribosomes prokaryotes B chloroplasts 80S ribosomes mitochondria circular DNA prokaryotes C prokaryotes circular DNA mitochondria circular DNA chloroplasts D prokaryotes 70S ribosomes chloroplasts 80S ribosomes mitochondria

Accepted Answer

C

Question 4

4 Which cell structures contain RNA? 1 centrioles 2 mitochondria 3 nucleus 4 ribosomes A 1, 2, 3 and 4 B 1 and 2 only C 2, 3 and 4 only D 3 and 4 only

Accepted Answer

C

Question 5

5 It is possible for a bacterium to synthesise a eukaryotic protein. This involves introducing a eukaryotic gene into the bacterial DNA. The eukaryotic gene is then translated by the bacterium. What explains why a bacterial cell can produce a eukaryotic protein but cannot produce a eukaryotic glycoprotein? A Bacteria do not have rough endoplasmic reticulum. B Bacteria do not have a nuclear envelope. C Bacteria do not have mitochondria. D Bacteria do not have Golgi bodies.

Accepted Answer

D

Question 6

6 Which structures are found in typical prokaryotic cells and also in typical plant cells? A cell walls B histones C telomeres D tonoplasts

Accepted Answer

A

Question 7

7 The molecule shown is a polymer of reducing sugars. CH2OH CH2OH CH2OH CH2OH O O O O OH OH OH OH O O O HO OH OH OH OH OH Which procedures could be carried out to show that this molecule is a polymer of reducing sugars? 1 Add hydrolytic enzyme and then heat with Benedict’s solution. 2 Dissolve in water, neutralise and then heat with Benedict’s solution. 3 Boil with hydrochloric acid, neutralise and then heat with Benedict’s solution. A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3 only

Accepted Answer

C

Question 8

8 Which statement about biological molecules is correct? A Amylopectin, amylose and cellulose are all polymers. B Amylose, cellulose and glucose are all macromolecules. C Cellulose, glucose and starch are all monomers. D Sucrose, starch and amylopectin are all polysaccharides.

Accepted Answer

A

Question 9

9 Sugars with a ring structure can also have a linear structure. H C O H C OH HO C H H C OH H C OH CH2OH Which of these sugar molecules could be represented by the linear structure in the diagram? 1 glucose 2 ribose 3 sucrose A 1 and 2 B 2 and 3 C 1 only D 2 only

Accepted Answer

C

Question 10

10 Which statements about phospholipids and triglycerides are correct? 1 They both contain ester bonds. 2 They both have three fatty acid chains per molecule. 3 They both may have saturated and unsaturated fatty acid chains. 4 They are both used only as storage molecules. A 1, 2 and 3 B 1 and 3 only C 2, 3 and 4 D 2 and 4 only

Accepted Answer

B

Question 11

11 The diagrams show three examples of different bonds. bond 1 bond 2 bond 3 O NH O C C N CH2 S S CH2 H Which bonds hold the secondary structure of proteins together? A 1, 2 and 3 B 1 and 2 only C 1 only D 2 and 3 only

Accepted Answer

C

Question 12

12 Hydrogen bonding explains many of the properties of water, including the high latent heat of vapourisation and high specific heat capacity. For which processes in plants is hydrogen bonding in water important on hot sunny days? 1 preventing denaturation of enzymes in leaves 2 reducing water loss by evaporation 3 allowing leaves to cool down quickly at night 4 holding the column of water in xylem vessels together A 1, 2, 3 and 4 B 1, 2 and 4 only C 1, 3 and 4 only D 2 and 3 only

Accepted Answer

B

Question 13

13 What is the most appropriate set of controls to use in an investigation into the rate of an enzyme-catalysed reaction over a range of temperatures from 25 °C to 65 °C? A enzyme and substrate at all temperatures tested B enzyme and boiled substrate at all temperatures tested C boiled enzyme only at all temperatures tested D substrate only at all temperatures tested

Accepted Answer

D

Question 14

14 An investigation is carried out with an enzyme at its optimum temperature and pH. The rate of the enzyme reaction is measured at different substrate concentrations. The investigation is repeated in the presence of a competitive inhibitor. How will the results with the competitive inhibitor be different from the original results? Km with competitive Vmax with competitive inhibitor inhibitor A higher lower B higher the same C the same lower D the same the same

Accepted Answer

B

Question 15

15 Which description of cell surface membrane permeability is correct? A An increase in the concentration of cholesterol molecules in the cell surface membrane can increase its permeability to hydrophilic substances. B Cell surface membrane permeability to large hydrophilic molecules is high and can be increased by membrane transport proteins involved in facilitated diffusion. C The permeability of the cell surface membrane to ions increases as the proportion of saturated fatty acid chains in the phospholipids increases. D Without the presence of carrier and channel membrane proteins, the cell surface membrane has a low permeability to large polar molecules.

Accepted Answer

D

Question 16

16 Which transport mechanism within a cell can occur in the absence of membranes? A active transport B diffusion C facilitated diffusion D osmosis

Accepted Answer

B

Question 17

17 A student measured the time taken for complete diffusion of a dye into agar blocks of different sizes. The results are shown in the table. size of agar block time for / mm × mm × mm diffusion / s 5 × 5 × 5 6.2 10 × 10 × 10 16.1 15 × 15 × 15 34.5 5 × 10 × 15 What is the predicted time for complete diffusion of the dye into the agar block measuring 5 mm × 10 mm × 15 mm? A 6.2 s B 16.1 s C 34.5 s D more than 34.5 s

Accepted Answer

A

Question 18

18 A plant cell with a water potential of –600 kPa was placed in a solution with a water potential of –410 kPa for 10 minutes. Which row is correct? net movement water potential effect on cell of water of cell A into cell becomes higher becomes turgid B into cell becomes lower bursts C out of cell becomes higher swells D out of cell becomes lower becomes plasmolysed

Accepted Answer

A

Question 19

19 Which cells contain telomeres that are longer than those in a helper T-lymphocyte secreting cytokines? 1 bone marrow stem cells 2 mature red blood cells 3 activated memory B-lymphocytes A 1 and 2 B 1 and 3 C 2 only D 3 only

Accepted Answer

B

Question 20

20 In which stage of the cell cycle are telomeres needed to prevent the loss of genes? A prophase B cytokinesis C G1 phase D S phase

Accepted Answer

D

Question 21

21 Which row shows part of the correct sequence of mitosis? A chromosomes nuclear chromosomes spindle fibres → line up at the → envelope → condense shorten equator disappears B chromosomes nuclear spindle fibres chromosomes line up at the → → → envelope shorten condense equator reappears C chromosomes nuclear spindle fibres chromosomes line up at the → → envelope → shorten uncoil equator reappears D nuclear chromosomes chromosomes spindle fibres → envelope → → line up at the uncoil shorten disappears equator

Accepted Answer

C

Question 22

22 What is correct for cytosine?

has a single ring

is a pyrimidine

joins to its
complementary base

structure with 3 hydrogen bonds
A v v v
B v x v
c x v x
D x x v

key
Y = correct
X = incorrect

Accepted Answer

A

Question 23

23 Scientists grew bacteria in a medium containing heavy nitrogen, 15N, as the only source of nitrogen. After many generations, both strands of all of the bacterial DNA molecules contained heavy nitrogen. These bacteria were then moved from the heavy nitrogen medium into a medium with only light nitrogen, 14N. The bacteria divided once to form the first generation and once more to form the second generation. A sample of bacteria was collected from the second generation and the DNA was analysed to find: ● the percentage of DNA strands that contained only light nitrogen ● the percentage of DNA molecules that contained light nitrogen and heavy nitrogen. Which row shows the results of this analysis? percentage of DNA strands percentage of DNA molecules that contained only light that contained light nitrogen nitrogen and heavy nitrogen A 50 25 B 50 50 C 75 25 D 75 50

Accepted Answer

D

Question 24

24 The table shows the tRNA anticodons for four amino acids. amino acid tRNA anticodons asparagine UUA, UUG glutamic acid CUU, CUC proline GGA, GGG, GGU, GGC threonine UGA, UGG, UGU, UGC A cell makes a polypeptide containing the amino acid sequence shown. asparagine – threonine – proline – glutamic acid Which sequence of bases on the transcribed strand of a DNA molecule could code for this part of the polypeptide? A AATACCCCTGAA B AATACCCCTCAA C TTACTTGGATGG D TTATGGGGACTT

Accepted Answer

D

Question 25

25 The photomicrograph shows a section of a plant organ. Students were asked to study the photomicrograph and identify the organ, giving a reason to support their answer. Which statement written by the students correctly identifies the organ and provides a correct reason to support this identification? A It is a leaf because the xylem is located on the inner side of each vascular bundle. B It is a stem because there is a ring of endodermis visible around the edge of the vascular tissue. C It is a stem because the vascular bundles are arranged in a ring near the epidermis. D It is a xerophytic leaf because there is a thick epidermis made up of many layers of cells.

Accepted Answer

C

Question 26

26 What is correct about the apoplastic pathway and symplastic pathway in a root? apoplastic pathway symplastic pathway A Casparian strip blocks water moves across the the movement of water root through cell walls B water moves across the water moves from cell to root through cell walls cell via the plasmodesmata C water moves from cell to water passes through cell via the plasmodesmata the cytoplasm D water passes through Casparian strip blocks the cytoplasm the movement of water

Accepted Answer

B

Question 27

27 Sucrose moves into a phloem sieve tube element from a leaf mesophyll cell. Which changes to the water potential and the volume of solution in the phloem sieve tube element are correct? water potential volume of becomes solution A higher decreases B higher increases C lower decreases D lower increases

Accepted Answer

D

Question 28

28 The photomicrograph shows three white blood cells labelled X, Y and Z. Y Z X Which row correctly identifies these cells? cell X cell Y cell Z A lymphocyte monocyte neutrophil B lymphocyte neutrophil monocyte C monocyte neutrophil lymphocyte D neutrophil monocyte lymphocyte

Accepted Answer

B

Question 29

29 Which row correctly identifies the locations in which a type of molecule or cell is present?

type of molecule or cell blood lymph tsue
antibody v v v key
large plasma protein Jv x J v = present
lymphocyte v v Xx X =not present
phagocyte x v Jv

Accepted Answer

A

Question 30

30 The graph shows the changes in pressure that occur in the left side of the heart during one cardiac cycle. key pressure left ventricle aorta left atrium 0 0 0.2 0.4 0.6 0.8 time / s At which time are the semi-lunar valves in the heart open? A 0.1 s B 0.3 s C 0.5 s D 0.7 s

Accepted Answer

B

Question 31

31 What would change the ratio of red blood cells to white blood cells in the blood of a healthy human? 1 development of leukaemia 2 infection with Variola 3 living for six months at high altitude A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3 only

Accepted Answer

A

Question 32

32 The diagram represents three types of cell found in the human gas exchange system. X Y Z Which of these cell types could be affected when a person is exposed to tar in cigarette smoke? A X, Y and Z B X and Z only C Y and Z only D Y only

Accepted Answer

A

Question 33

33 The photomicrograph shows part of the lung as seen using a light microscope. 2 1 3 Which row correctly identifies the features labelled 1, 2 and 3? 1 2 3 A alveolus capillary bronchiole B alveolus bronchiole capillary C bronchiole small artery alveolus D small artery bronchiole alveolus

Accepted Answer

C

Question 34

34 How many times must a molecule of oxygen pass through a cell surface membrane as it diffuses from inside an alveolus, through a cell in the capillary wall, to bind to a molecule of haemoglobin? A 3 B 4 C 5 D 10

Accepted Answer

C

Question 35

35 A disease is an abnormal disruption to the functioning of an organism or part of an organism. Which disruption to function is an example of an infectious disease? A Airflow to one lung is disrupted by uncontrolled cell division forming a mass of cells. B Airways become inflamed due to exposure to smoke. C Oxygen transport is disrupted due to changes in protein shape in red blood cells. D Lung tissue is disrupted by the multiplication of prokaryotic cells.

Accepted Answer

D

Question 36

36 The number of people at risk of contracting malaria has increased due to an increase in the distribution of Anopheles mosquitoes. What could be the cause of this increase in the distribution of Anopheles mosquitoes? A antibiotic resistance B drug resistance in Plasmodium C no effective vaccine D global warming

Accepted Answer

D

Question 37

37 Which diseases are treated with antibiotics? cholera A B D TB measles C

Accepted Answer

A

Question 38

38 Which row correctly describes B-lymphocytes?

release antibodies
immediately after
formation

processed in
the thymus

Jv key
JY =correct

X = incorrect

x { x

Accepted Answer

D

Question 39

39 Which features of monoclonal antibodies are important to their use in the treatment of cancer?

1 They can bind to tumour-associated antigens.

2 They can distinguish between different strains of pathogens.

3 They can deliver drugs to specific targets.

1

3

0 Oo WwW >

Ke 44

~*~ <x <li

«x < & x

key
¥ = is important

X = is not important

Accepted Answer

B

Question 40

40 A student was asked to explain why vaccination has successfully eradicated smallpox but not other diseases, such as measles, malaria and sickle cell anaemia. These are the statements made by the student. 1 The antigens of the virus causing smallpox did not change, unlike the antigens of the virus causing measles. 2 Sickle cell anaemia has many different types of mutation, unlike smallpox, so each would require a vaccine. 3 Unlike smallpox, malaria involves animals as part of the transmission cycle and this makes the cycle harder to break. 4 The vaccine against measles often causes a poor primary immune response so that booster vaccines are required, unlike the vaccine against smallpox. Which statements are possible explanations? A 1, 3 and 4 B 1 and 2 C 1 and 4 only D 2 and 4

Accepted Answer

A

Question paper16 pages

Mark scheme3 pages

Questions as text

Q1 · The diagram shows an eyepiece graticule and cell viewed through a microscope

Q2 · Which cell structures can form vesicles?

Q3 · The diagram shows three circles, 1, 3 and 5, representing chloroplasts, mitochondria and…

Q4 · Which cell structures contain RNA?

Q5 · It is possible for a bacterium to synthesise a eukaryotic protein

Q6 · Which structures are found in typical prokaryotic cells and also in typical plant cells?

Q7 · The molecule shown is a polymer of reducing sugars

Q8 · Which statement about biological molecules is correct?

Q9 · Sugars with a ring structure can also have a linear structure

Q10 · Which statements about phospholipids and triglycerides are correct?

Q11 · The diagrams show three examples of different bonds

Q12 · Hydrogen bonding explains many of the properties of water, including the high latent heat…

Q13 · What is the most appropriate set of controls to use in an investigation into the rate of…

Q14 · An investigation is carried out with an enzyme at its optimum temperature and pH

Q15 · Which description of cell surface membrane permeability is correct?

Q16 · Which transport mechanism within a cell can occur in the absence of membranes?

Q17 · A student measured the time taken for complete diffusion of a dye into agar blocks of…

Q18 · A plant cell with a water potential of –600 kPa was placed in a solution with a water…

Q19 · Which cells contain telomeres that are longer than those in a helper T-lymphocyte…

Q20 · In which stage of the cell cycle are telomeres needed to prevent the loss of genes?

Q21 · Which row shows part of the correct sequence of mitosis?

Q22 · What is correct for cytosine?

Q23 · Scientists grew bacteria in a medium containing heavy nitrogen, 15N, as the only source…

Q24 · The table shows the tRNA anticodons for four amino acids

Q25 · The photomicrograph shows a section of a plant organ

Q26 · What is correct about the apoplastic pathway and symplastic pathway in a root?

Q27 · Sucrose moves into a phloem sieve tube element from a leaf mesophyll cell

Q28 · The photomicrograph shows three white blood cells labelled X, Y and Z

Q29 · Which row correctly identifies the locations in which a type of molecule or cell is…

Q30 · The graph shows the changes in pressure that occur in the left side of the heart during…

Q31 · What would change the ratio of red blood cells to white blood cells in the blood of a…

Q32 · The diagram represents three types of cell found in the human gas exchange system

Q33 · The photomicrograph shows part of the lung as seen using a light microscope

Q34 · How many times must a molecule of oxygen pass through a cell surface membrane as it…

Q35 · A disease is an abnormal disruption to the functioning of an organism or part of an…

Q36 · The number of people at risk of contracting malaria has increased due to an increase in…

Q37 · Which diseases are treated with antibiotics?

Q38 · Which row correctly describes B-lymphocytes?

Q39 · Which features of monoclonal antibodies are important to their use in the treatment of…

Q40 · A student was asked to explain why vaccination has successfully eradicated smallpox but…

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