Cambridge A Level Biology 9700 — 2023 May/June Paper 1 · Variant 3

1 Which feature is visible with a light microscope using a natural light source? A DNA molecule of diameter 2 nm B Paramecium cell of diameter 200 µm C phospholipid bilayer of width 8 nm D ribosome of diameter 20 nm

Mark scheme: B

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2 The electron micrograph shows a structure found in the cytoplasm of an animal cell. Which biological molecules are found in this structure? 1 nucleic acids 2 proteins 3 phospholipids A 1 and 3 B 1 only C 2 and 3 D 2 only

Mark scheme: D

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3 Which cell structures contain nucleic acid? 1 cytoplasm 2 lysosomes 3 mitochondria A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 3 only

Mark scheme: C

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4 Mitochondria are thought to have evolved from prokaryotic cells that were ingested by an ancestral cell. Which feature have prokaryotes lost during their evolution into mitochondria? A cell wall B circular chromosome C endoplasmic reticulum D ribosomes

Mark scheme: A

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5 Which polymers are present in all viruses, all prokaryotes and all eukaryotes? 1 polynucleotides 2 polypeptides 3 polysaccharides A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3 only

Mark scheme: B

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6 How many of the listed structures typically contain genetic material that has telomeres? • bacterial cell • chloroplast • mitochondrion • nucleus A 1 B 2 C 3 D 4

Mark scheme: A

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7 Steps 1, 2, 3 and 4 are used to test for a non-reducing sugar. 1 Put 5 cm3 of solution into a test-tube. 2 Add a few drops of acid. 3 Neutralise with alkali. 4 Add 6 cm3 of Benedict’s solution. When is the solution heated or boiled? A between steps 1 and 2 B between steps 2 and 3, and after step 4 C between steps 2 and 3 only D after step 4 only

Mark scheme: B

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8 Which features contribute to the function of a cellulose molecule? 1 Long chains of glucose molecules coil into a helix. 2 Many hydrogen bonds form between adjacent chains. 3 It is insoluble in water. A 1, 2 and 3 B 1 and 3 only C 2 and 3 only D 2 only

Mark scheme: C

More questions on Carbohydrates and lipids

9 What correctly describes triglycerides? A non-polar molecules that are soluble in ethanol B non-polar molecules that are soluble in water C polar molecules that are soluble in ethanol D polar molecules that are soluble in water

Mark scheme: A

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10 Cocoa butter contains three different triglycerides. These triglycerides are made from the fatty acids: • oleic acid (O) • palmitic acid (P) • stearic acid (S). The three triglycerides found in cocoa butter are POS, SOS and POP. The chemical structure of the triglyceride POS is shown next to a diagrammatic representation of POS. H O H H H H H H H H H H H H H H H H C O C C C C C C C C C C C C C C C C H G P H H H H H H H H H H H H H H H L Y O H H H H H H H H H H H H H H H H H C H C O C C C C C C C C C C C C C C C C C C H O E H H H H H H H H H H H H H H H R O H H H H H H H H H H H H H H H H H O H C O C C C C C C C C C C C C C C C C C C H L S H H H H H H H H H H H H H H H H H H Which statement is correct? A Triglyceride POP contains two unsaturated fatty acids joined by ester bonds to glycerol. B Triglyceride POS contains two less carbon atoms than triglyceride POP. C Triglyceride SOS contains four more carbon atoms than triglyceride POP. D Triglyceride SOS contains two saturated fatty acids joined by hydrolysis to glycerol.

Mark scheme: C

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11 Which molecules contain at least four double bonds? unsaturated triglyceride C A D haemoglobin collagen B

Mark scheme: D

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12 The diagram shows the amino acid glutamic acid. COOH H C CH2 CH2 COOH NH2 What is the R group for glutamic acid? A NH2 B H C COOH D CH2 CH2 COOH

Mark scheme: D

More questions on Proteins

13 The diagram shows three interactions that hold protein molecules in shape. N H NH3 + O S S interaction 1 interaction 3 C COO– S S interaction 2 Which row identifies these interactions? interaction 1 interaction 2 interaction 3 A hydrogen bond disulfide bond hydrophobic interaction B hydrogen bond covalent bond ionic bond C hydrophobic interaction ionic bond hydrogen bond D ionic bond disulfide bond peptide bond

Mark scheme: B

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14 Some animals produce antimicrobial proteins which protect them from pathogens. These proteins could be used to kill human pathogens, however when used as a medicine they are broken down by protein-digesting enzymes. Replacing one of the amino acids found in the protein with an amino acid that had been synthesised in the laboratory resulted in a modified protein that was not broken down. What could explain why this modified protein was not broken down by the protein-digesting enzymes? 1 The modified protein has a different tertiary structure to the original protein. 2 The modified protein is not complementary in shape to the enzyme’s active site. 3 The modified protein is unable to induce a fit with the protein-digesting enzyme. A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3 only

Mark scheme: A

More questions on Factors that affect enzyme action

15 A student investigated the effect of substrate concentration on the rate of an enzyme-catalysed reaction. A graph was plotted to show the relationship between these two variables. The student was asked to take readings from the graph that could be used to determine the Michaelis–Menten constant, Km, for this enzyme. J, K, L and M show points read from the graphs which the student could use to determine the value of Km. J rate of rate of reaction reaction 0 0 K 0 0 concentration concentration of substrate of substrate rate of rate of reaction reaction L 0 0 M 0 0 concentration concentration of substrate of substrate Which two readings must the student use to determine the value of Km? A J and K B J and M C K and L D L and M

Mark scheme: C

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16 The end-product of a metabolic pathway can act as a competitive inhibitor. This is called end-product inhibition and allows a cell to control a metabolic pathway. The diagram shows a metabolic pathway where the end-product could act as an inhibitor of enzyme W. substrate enzyme W intermediate 1 enzyme X intermediate 2 inhibition enzyme Y intermediate 3 enzyme Z end-product What would be the effect if enzyme Z was inhibited by the end-product instead of enzyme W? quantity of quantity of intermediate 1 end-product A increase decrease B increase unchanged C decrease decrease D decrease unchanged

Mark scheme: A

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17 Which row shows the distribution of cholesterol and the carbohydrate chains of glycolipids and glycoproteins in a cell surface membrane? carbohydrate chains carbohydrate chains cholesterol of glycolipids of glycoproteins A between phospholipid mainly on the mainly on the heads only outer surface inner surface B between phospholipid mainly on the mainly on the heads only inner surface outer surface C between phospholipids mainly on the mainly on the inner surface inner surface D between phospholipids mainly on the mainly on the outer surface outer surface

Mark scheme: D

More questions on Fluid mosaic membranes

18 Which row correctly describes all the possible relative concentrations of a substance when the substance is moved by endocytosis or exocytosis? endocytosis exocytosis A concentrations equal concentrations equal B concentrations equal, concentrations equal, greater inside or greater inside or greater outside greater outside C concentrations equal concentrations equal or greater outside or lower outside D concentrations equal concentrations equal or lower outside or greater outside

Mark scheme: B

More questions on Movement into and out of cells

19 Which statement about simple diffusion is correct? A It requires specific molecules in the cell surface membrane. B It is a passive mode of transporting substances. C It always requires a membrane for transport of substances. D It only happens in the cells of prokaryotes and eukaryotes.

Mark scheme: B

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20 Plant cells with the same water potential in their cytoplasm were each put into one of three different concentrations of sugar solution, 10%, 5% and 2.5%. The cells were left for 50 minutes and then observed using a light microscope. cell X cell Y cell Z vacuole Which statements are correct? 1 Cell Y had a lower water potential than the sugar solution it was put into. 2 Cell Z was put into the 10% sugar solution. 3 Cell Z had a less negative water potential than the sugar solution it was put into. A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3 only

Mark scheme: A

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21 Which row describes some properties of stem cells? able to divide by mitosis to produce more stem cells able to differentiate into specialised cells able to repair damaged cells 0 0O WwW D> ~*~ KKK v v x x Ke O&K key ¥ = is a property X = is not a property

Mark scheme: B

More questions on Replication and division of nuclei and cells

22 The mitotic index is a measure of the proportion of cells that are undergoing mitosis in an area of tissue. It is calculated using the formula shown. mitotic index = (number of cells undergoing mitosis ÷ total number of cells) × 100 A scientist calculated the mitotic index of areas of onion root at different distances from the tip of the root. The results are shown. 14 12 10 8 mitotic index 6 4 2 0 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 distance from tip of root / mm Which statement is correct? A No cell division occurs further than 1.4 mm from the tip of the root. B The rate of cell division decreases as the distance from the root tip decreases. C Most of the cells undergoing cell division are closer to the tip of the root. D For a sample of 200 cells 0.2 mm from the tip of the root, 6 would be undergoing mitosis.

Mark scheme: C

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23 Which molecules make up the structure of ATP? 1 adenine 2 thymine 3 deoxyribose 4 phosphate 5 ribose A 1, 2 and 3 B 1, 3 and 4 C 1, 4 and 5 D 2, 4 and 5

Mark scheme: C

More questions on Structure of nucleic acids and replication of DNA

24 A short piece of DNA, 19 base pairs long, was analysed to find the number of nucleotide bases in each of the polynucleotide strands. Some of the results are shown. number of nucleotide bases A C G T strand 1 4 strand 2 7 5 How many cytosines were in strand 1? A 2 B 3 C 5 D 7

Mark scheme: B

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25 Which statement about the role of DNA polymerase in the process of semi-conservative replication of DNA is correct? A DNA polymerase forms the hydrogen bonds between complementary base pairs. B DNA polymerase moves along the lagging strand in the 3′ to 5′ direction. C DNA polymerase joins new bases to the leading strand only. D DNA polymerase moves along leading and lagging strands in the 5′ to 3′ direction.

Mark scheme: D

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26 The diagram shows the process of translation occurring at a ribosome. ribosome S C A U U C G C U A A U G What is the base sequence at S? A CUA B CAT C GAU D GAT

Mark scheme: C

More questions on Protein synthesis

27 Which row correctly explains how the structures of phloem sieve tube elements and xylem vessel elements are related to their functions as transport systems? phloem sieve tube elements xylem vessel elements A contain mitochondria to make ATP cell walls are thickened and for the active loading of sucrose contain lignin which makes into the phloem xylem vessels waterproof B contain no nucleus so that end walls between cells are dissolved solutes can move easily perforated so that water can move through cells easily through xylem vessels C end walls between cells are lignin in cell walls gives strength so perforated so that dissolved solutes that xylem vessels do not collapse can move between cells due to transpiration pull D no end walls between cells so that contain no cytoplasm so that a sucrose solution can move up and continuous column of water can down the phloem move up the xylem vessels

Mark scheme: C

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28 Which component of plants is used by the apoplast pathway as water is moved from the soil to the xylem? A Casparian strip B cellulose C endodermis D suberin

Mark scheme: B

More questions on Transport mechanisms

29 Which statements correctly describe transport pathways in dicotyledonous plants? 1 In the symplast pathway, water may move through intercellular spaces. 2 The symplast pathway may be blocked by the tonoplast. 3 In the apoplast pathway, water does not move through plasmodesmata. 4 The apoplast pathway may be blocked by the Casparian strip. A 1 and 2 B 1 and 4 C 2 and 3 D 3 and 4

Mark scheme: D

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30 Plants, such as the tobacco plant, retain very little of the water they take in and the volume of water lost during transpiration is very high. This is because these plants can only absorb carbon dioxide through open stomata. Plants use carbon dioxide to synthesise glucose molecules. It is estimated that 400 molecules of water are lost for each carbon dioxide molecule gained. How many water molecules are lost for a plant to synthesise one molecule of glucose? A 800 B 1200 C 2000 D 2400

Mark scheme: D

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31 Which changes occur as sucrose is transferred from leaves into phloem sieve tubes to be transported to a sink? water potential volume of liquid in phloem sieve in phloem tubes becomes sieve tubes A less negative decreases B less negative increases C more negative decreases D more negative increases

Mark scheme: D

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32 The graph shown does not have any axis labels. 0 0 Which row shows appropriate labels for the axes that would explain mass flow in phloem? x-axis y-axis A distance from sink / m hydrostatic pressure / kPa B hydrostatic pressure / kPa distance from sink / m C distance from source / m hydrostatic pressure / kPa D hydrostatic pressure / kPa distance from source / m

Mark scheme: C

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33 What is present in the blood in human veins? 1 chloride ions 2 carbonic anhydrase 3 oxyhaemoglobin A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3 only

Mark scheme: A

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34 The photomicrograph shows two blood vessels P and Q. Both these blood vessels are part of a network which transports blood around the body. Q Q P Which row is correct for blood vessel P and blood vessel Q? blood vessel P blood vessel Q A carries blood into arterioles carries blood into arterioles B carries blood into arterioles carries blood from venules C carries blood from venules carries blood into arterioles D carries blood from venules carries blood from venules

Mark scheme: C

More questions on The circulatory system

35 The diagram shows a blood capillary and the tissue fluid which surrounds it. tissue fluid W X arteriole venule Z blood capillary Y end end tissue fluid Tissue fluid is formed when fluid and solutes from blood plasma pass through tiny gaps in the capillary wall. Most tissue fluid is then returned to the blood in the capillary. Which pressures will be needed at points W, X, Y and Z so that this system can function? pressure at W pressure at X pressure at Y pressure at Z / mm Hg / mm Hg / mm Hg / mm Hg A 18 26 36 26 B 26 26 18 36 C 26 36 26 18 D 36 18 26 26

Mark scheme: B

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36 What happens during ventricular systole in a mammalian heart? A Aortic pressure increases. B Atrioventricular valves open. C Semilunar valves close. D Ventricular pressure decreases.

Mark scheme: A

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37 The photomicrograph shows a part of the human gas exchange system with one tissue labelled P. P Which row is correct? part of gas function of tissue P exchange system A bronchus regulates the amount of air reaching the lungs B bronchus provides support and prevents collapse C bronchiole regulates the amount of air reaching the lungs D bronchiole provides support and prevents collapse

Mark scheme: C

More questions on The gas exchange system

38 How many times must a molecule of oxygen pass through a cell surface membrane as it diffuses from the airspace 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

Mark scheme: C

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39 A student wrote four statements about cholera. Which statement is not correct? A It can be controlled by vaccination. B It is caused by bacteria spread by ingestion. C HIV/AIDS increases the risk of infection. D It may be transmitted by animal vectors.

Mark scheme: D

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40 Monoclonal antibodies are produced using the hybridoma method. What are removed from the spleen of a mouse to produce monoclonal antibodies? A antigens B clones C lymphocytes D myeloma cells

Mark scheme: C

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