Biology 9700/12 October/November 2021: question paper and mark scheme

Question

A scale bar on an electron micrograph is 2 cm long and represents an actual length of 1 μm. What is the magnification of the electron micrograph? A ×200 B ×2000 C ×20 000 D ×200 000

Question

The eyepiece of a microscope is fitted with an eyepiece graticule and a stage micrometer scale is placed on the microscope. Which statements about the stage micrometer scale are correct? 1 The scale can be used to measure the actual length of cells directly. 2 The scale allows you to calibrate the eyepiece graticule. 3 Less of the scale is visible as the objective lens changes from ×10 to ×40. A 1, 2 and 3 B 2 and 3 only C 1 only D 2 only

Question

Four students were asked to match the function with the appearance of some cell structures in an animal cell. The functions were listed by number. 1 mRNA passes through to the ribosome 2 organises microtubules to produce the spindle during cell division 3 synthesis of polypeptides The appearances were listed by letter. V membranes which surround an enclosed inner cavity W non-membrane bound, spherical structures X a double membrane interspersed with pores Y non-membrane bound, cylindrical structures Z membrane-bound sacs, arranged as a flattened stack Which student correctly matched the numbered function with the appearance of the cell structure? 1 2 3 A V W X B V Y Z C X W Z D X Y W

Question

Which cell structures are required for the formation of lysosomes and the hydrolytic enzymes that they contain? mitochondria rough B endoplasmic Golgi reticulum A D C body

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Which cell structures contain rRNA? 1 chloroplast 2 mitochondrion 3 nucleus 4 smooth endoplasmic reticulum A 1, 2, 3 and 4 B 1, 2 and 3 only C 1, 2 and 4 only D 3 and 4 only

Question

The single-celled organism Thiomargarita namibiensis measures 700 μm in diameter and is enclosed in a cell wall. The genetic material of T. namibiensis is located free in the cytoplasm where it occurs as thousands of copies of circular DNA. Most of the cell is taken up by a large vacuole, which stores essential chemicals for metabolism. Which statement is correct? A It must be a eukaryote because a diameter of 700 μm is too large for a prokaryote. B It must be a plant because it contains a vacuole. C It must be a plant because it is enclosed in a cell wall. D It must be a prokaryote because its DNA is circular and located in the cytoplasm.

Question

A student carried out four tests on a sample of biological molecules. test observation emulsion cloudy Benedict’s yellow biuret purple iodine yellow Which conclusions made by the student are correct? 1 Fat was present. 2 Glucose was present. 3 Protein was present. 4 Starch was not present. A 1, 2, 3 and 4 B 1, 2 and 4 only C 1, 3 and 4 only D 2 and 3 only

Question

Which general formula is correct for monosaccharides such as fructose? A (CHO)n B (CH2O)n C (CHO2)n D (C2HO)n

Question

Which statements can be used to describe the structure of cellulose? 1 a polymer of glucose monomers linked by β-1,4 glycosidic bonds 2 a polysaccharide of hexose monomers 3 an unbranched macromolecule made of β-glucose monomers A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3 only

Question

Complete hydrolysis of polysaccharides requires all the glycosidic bonds between the monomers to be broken. Enzyme X only breaks α-1,4 glycosidic bonds. Which row shows how completely enzyme X can hydrolyse molecules of glycogen and amylose? glycogen amylose A + ++ key B ++ + – no hydrolysis C ++ – + some hydrolysis D – + ++ most hydrolysis

Question

Which molecules contain at least two double bonds? A saturated fatty acid, collagen and haemoglobin B collagen and saturated fatty acid only C haemoglobin and collagen only D saturated fatty acid and haemoglobin only

Question

The diagram shows an amino acid. H CH3 O N C C H H OH Which group is changed to produce different amino acids? A OH B C=O C CH3 D NH2

Question

Which row is correct about the structure of proteins? primary secondary tertiary quaternary A determined by occurs by disulfide, ionic, always formed by the sequence of hydrogen bonding hydrogen bonds association of two DNA nucleotides between NH and and hydrophobic or more C=O groups of interactions are all polypeptides amino acids involved B the number of in a single the bonds are always formed by amino acids in polypeptide it is formed at specific two or more each polypeptide either an α-helix points determined polypeptides held chain or a β-pleated by the primary together by bonds sheet structure formed between the polypeptides C formed by an α-helix is only globular always formed twenty different formed by proteins have this by two or amino acids hydrogen bonds level of structure more different linked in a between side polypeptides to specific order chains of give the final shape amino acids D the sequence a β-pleated sheet reactions between always formed of amino acids in is the result of a side chains of by two or each polypeptide folded specific amino more polypeptides chain polypeptide acids give a and a metal ion forming hydrogen specific 3-D shape bonds between adjacent strands

Question

Which graph correctly shows possible changes in energy levels as a chemical reaction progresses with or without an enzyme? A B energy levels S energy levels P S P progress of reaction progress of reaction C D energy levels S energy levels S P P progress of reaction progress of reaction key with enzyme without enzyme S substrate P product

Question

The graph shows the relationship between the concentration of substrate and the rate of an enzyme-catalysed reaction. rate of enzyme-catalysed reaction 0 0 concentration of substrate Which row shows how Km and Vmax for this enzyme would be affected if the same reaction was carried out in the presence of a competitive inhibitor? Km Vmax A increases decreases B increases remains the same C remains the same decreases D remains the same remains the same

Question

Liver cells contain vesicles that have proteins in their membranes which are specific for the transport of glucose. When these cells need to take up glucose, the vesicles fuse with the cell surface membrane. How does the uptake of glucose occur? A exocytosis B diffusion C endocytosis D facilitated diffusion

Question

A student set up an experiment to investigate diffusion. A block of agar, 1.0 cm × 1.0 cm × 1.0 cm, was stained uniformly with a water-soluble blue dye. The block of agar was put into a test-tube containing 10 cm3 of distilled water at 20 °C. The intensity of the blue colour of the water after five minutes was measured. Four other experiments, A, B, C and D, were then carried out using different numbers of agar blocks, different sizes of agar blocks and different temperatures. All other variables were standardised. Which experiment would give a lighter blue colour in the water after five minutes compared to the first experiment? size of each number of temperature of agar block / cm agar blocks distilled water / °C A 0.5 × 0.5 × 0.5 8 30 B 0.5 × 0.5 × 0.5 2 20 C 0.5 × 1.0 × 1.0 2 30 D 2.0 × 1.0 × 1.0 1 20

Question

Which description is correct? A A centromere holds two chromatids together until the end of prophase and attaches to the microtubules of the spindle. B A chromatid is one of two identical parts of a chromosome and is made of proteins and two molecules of DNA. C A chromosome is a structure with two identical parts, made of DNA and proteins, found in the nucleus of a prokaryotic cell. D A telomere is a sequence of DNA nucleotides, such as GGGTAA, repeated many times and found at the ends of each chromatid.

Question

During metaphase, a scientist stains the chromosomes of a diploid animal cell with fluorescent dye to allow the telomeres to be observed. This cell has 26 chromosomes. How many telomeres will the scientist observe? A 26 B 52 C 78 D 104

Question

The photomicrographs show cells in various stages of the cell cycle. 1 2 3 4 Which cells contain twice as many DNA molecules as a cell from the same organism that has just finished a complete mitotic cell cycle ending with cytokinesis? A 1, 2, 3 and 4 B 1, 2 and 4 only C 1 and 3 only D 2 and 4 only

Question

Uncontrolled cell division can result in the formation of a tumour. Which part of the cell cycle would take less time during the formation of a tumour? A cytokinesis B interphase C mitosis D telophase

Question

A piece of a DNA molecule contains 84 base pairs. The table shows the number of adenine and cytosine bases in one or both of the DNA strands in this piece of DNA molecule. base strand 1 strand 2 adenine 28 23 cytosine 15 How many guanine bases are present in this piece of DNA molecule? A 18 B 33 C 36 D 41

Question

The mRNA sequences of the three stop codons are shown. UAA UAG UGA Which mutation in the template (transcribed) strand of a DNA sequence that codes for a polypeptide would cause translation to stop prematurely? A ATT changed to ATC B ACT changed to ACA C ACC changed to ATT D ATC changed to TAG

Question

Which features of companion cells are essential to their function? 1 They are connected to the sieve tube elements by plasmodesmata. 2 They have a thicker cell wall than a sieve tube element. 3 They contain a nucleus and mitochondria. A 1 and 2 B 1 and 3 C 1 only D 2 and 3

Question

Which statements about water movement in plants are correct? 1 Water can pass through cellulose cell walls. 2 Water cannot pass through lignified cell walls. 3 Water can pass through cell walls that contain suberin. A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3 only

Question

The diameter of a tree trunk usually decreases slightly during the day. Which changes in environmental factors during the day could cause the diameter to decrease even more? increased humidity C A D increased increased wind speed B temperature

Question

Which sequence of events could lead to mass flow in a phloem sieve tube? 1 Sucrose moves into a sieve tube element. 2 Protons (H+) and sucrose molecules move into a companion cell through a co-transporter protein. 3 A very high hydrostatic pressure is produced. 4 The water potential of the sieve tube element decreases. 5 Protons (H+) are actively pumped out of a companion cell. 6 Water moves down a water potential gradient by osmosis. A 1→2→5→6→4→3 B 3→1→2→5→6→4 C 3→5→1→2→4→6 D 5→2→1→4→6→3

Question

What will happen as a result of the blood pressure in the right ventricle becoming higher than the blood pressure in the right atrium? A The semilunar valve in the aorta will close. B The semilunar valve in the pulmonary artery will close. C The left atrioventricular valve will close. D The right atrioventricular valve will close.

Question

The graph shows pressure changes in different parts of the heart during a mammalian cardiac cycle. W, X, Y and Z indicate when a valve opens or closes. Y X key aorta pressure ventricle atrium Z W 0 0.2 0.4 0.6 0.8 time / s Which row correctly identifies W, X, Y and Z? W X Y Z A atrioventricular atrioventricular semilunar semilunar valve opens valve closes valve opens valve closes B atrioventricular semilunar semilunar atrioventricular valve closes valve opens valve closes valve opens C semilunar semilunar atrioventricular atrioventricular valve opens valve closes valve opens valve closes D semilunar atrioventricular atrioventricular semilunar valve closes valve opens valve closes valve opens

Question

Which statements are correct? 1 Compared with blood, tissue fluid has less protein and no red blood cells. 2 Lymph may contain lipids, carbon dioxide and phagocytes. 3 Tissue fluid contains glucose, amino acids, urea and carbon dioxide. A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3 only

Question

Which statements about the formation of haemoglobinic acid are correct? 1 It can only occur with the dissociation of oxygen from haemoglobin. 2 It removes excess hydrogen ions, preventing blood from becoming too acidic. 3 It is linked to the action of carbonic anhydrase. A 1, 2 and 3 B 1 and 2 only C 1 only D 2 and 3 only

Question

What explains how the maximum volume of oxygen is taken up as blood passes through the capillaries of the lungs? A Each haemoglobin molecule can temporarily bind to four oxygen atoms. B The dissociation of carbon dioxide from carboxyhaemoglobin allows more haemoglobin to be available for binding oxygen. C The binding of the first oxygen molecule to haemoglobin decreases the affinity of haemoglobin for binding other oxygen molecules. D Oxyhaemoglobin formation increases the ability of red blood cells to transport oxygen.

Question

The image shown is a photomicrograph of a transverse section of part of the gas exchange system. What describes the image? A a thin inner layer of ciliated epithelial cells on top of a layer containing cartilage, supported by elastic fibres B a very thin epithelial lining with walls containing elastic fibres, surrounded by many blood vessels C an inner layer of ciliated epithelial and goblet cells on top of elastic fibres, supported by an outer layer consisting of cartilage D an inner layer of ciliated epithelial and goblet cells on top of loose tissue with mucous glands, supported by a continuous ring of cartilage

Question

Which row shows the tissues that are present in the wall of the trachea and the wall of the bronchus? smooth squamous goblet muscle epithelium cells A key B = present C = not present D

Question

When a person suffers an asthma attack, the tubes of the gas exchange system narrow and extra mucus is produced. Which changes occur during an asthma attack? 1 Activity of ciliated epithelium increases. 2 Endocytosis in goblet cells increases. 3 Smooth muscles are more active. A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3 only

Question

Which flow diagram correctly describes the effect of tar entering the lungs? carcinogens come into mutation uncontrolled A → → contact with occurs cell division DNA mucus goblet cells phagocytes accumulates B secrete more → → attracted by causing mucus inflammation infection mucus phagocytes elastase C accumulates → attracted by → destroys the causing infection inflammation alveolar walls phagocytes causes mutation D → attracted by → irritation and occurs inflammation coughing

Question

Which control measures would reduce the transmission of tuberculosis (TB)? boiling water antibiotics vaccination before drinking it A yes no no B yes yes yes C no yes no D no yes yes

Question

Comorbidity is where an individual has two or more diseases or medical conditions at the same time. Some medical conditions are particularly likely to result in comorbidity. In one example, initial infection with one pathogen can increase the risk of developing a second disease by a factor of 15 or more. The second disease is then the major cause of death for these people. Which description could fit this example? A cholera infection followed by development of malaria B cholera infection followed by development of AIDS C HIV infection followed by development of TB D malaria infection followed by development of TB

Question

Which conditions are infectious and result in a high white blood cell count? 1 leukaemia 2 myasthenia gravis 3 TB A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 3 only

Question

Which cell type causes the secondary immune response to be much faster than the primary immune response? A helper T-lymphocyte B memory cell C phagocyte D plasma cell