2024 AQA AS BIOLOGY PAPER 1 EXAM QUESTIONS WITH CORRECT ANSWERS, Exams of Advanced Education

Download 2024 AQA AS BIOLOGY PAPER 1 EXAM QUESTIONS WITH CORRECT ANSWERS and more Exams Advanced Education in PDF only on Docsity!

2024 AQA AS BIOLOGY PAPER 1

EXAM QUESTIONS WITH CORRECT

ANSWERS







Describe a biochemical test to show that raffinose solution contains a non- reducing sugar. - CORRECT-ANSWERSFirst heat the sample with an acid in a water bath and neutralise, then heat with Benedict solution in a water bath for five minutes. A positive test should produce a red precipitate. Human papilloma virus (HPV) is the main cause of cervical cancer. A vaccine has been developed to protect girls and women from HPV. Describe how giving this vaccine leads to production of antibody against HPV - CORRECT- ANSWERS1. Vaccine/it contains antigen (from HPV);

2. Displayed on antigen-presenting cells;
3. Specific helper T cell (detects antigen and) stimulates specific B cell;
4. B cell divides/goes through mitosis/forms clone to give plasma cells;
5. B cell/plasma cell produces antibody; Doctors investigated whether it was better to give two or three doses of the HPV vaccine. They determined the mean concentration of antibody against HPV in blood samples from girls who were given either two or three doses of the vaccine.
   • Girls given two doses received an initial vaccination, followed by a second at 6 months.
   • Girls given three doses received an initial vaccination, followed by a second at 1 month and a third at 6 months. The doctors measured the concentration of antibody each month. The results are shown in Figure 5. What do these results suggest about whether it is better to give two or three doses of the vaccine? Give reasons for your answer - CORRECT-ANSWERS1. Two (doses) because got more antibody; 2. With three doses, second dose/dose at 1 month doesn't lead to production of any more antibody (than the twodose group)/get same/similar response; 3. Three doses would be more expensive/less popular with parents/girls (and serves no purpose);

The doctors carried out a statistical test to determine whether the antibody concentrations were significantly different in girls given two doses of the vaccine, compared with those given three doses. They determined the mean concentrations of antibody 9 months after the first dose of vaccine. What statistical test should the doctors have used? Give the reason for your choice. - CORRECT-ANSWERSt-test, because comparing two means; There is genetic diversity within HPV. Give two ways doctors could use base sequences to compare different types of HPV. - CORRECT-ANSWERS1. Compare (base sequences of) DNA;

2. Look for mutations/named mutations (that change the base sequence);
3. Compare (base sequences of) (m)RNA; Chromosomes line up on the equator of the mitotic spindle in... - CORRECT- ANSWERSmetaphase Suggest why the development of a monopolar mitotic spindle would prevent successful mitosis. - CORRECT-ANSWERS1. No separation of chromatids/chromosomes/centromeres;
4. Chromatids/chromosomes all go to one pole/end/sides of cell/not pulled to opposite poles;
5. Doubles chromosome number in cell/one daughter cell gets no chromosomes or chromatids; A student who saw these results concluded that in any future trials of this kinesin inhibitor with people, a concentration of 100 nmol dm-3 would be most appropriate to use. Do these data support the student's conclusion? Give reasons for your answer - CORRECT-ANSWERS1. (No, because) at 100 there are still some (7%) cancer cells dividing/undergoing mitosis;
6. So, cancer not destroyed/may continue to grow/spread/form tumours;
7. Best concentration may be between 100 and 1000/need trials between 100 and 1000;
8. This research in culture, don't know effect of KI on people;
9. (Yes, because) above 100 produces little increase in % of cells not dividing/undergoing mitosis/at 100, most (93%) cancer cells unable to divide/dead;
10. Above 100 may be harmful (to body);
11. Higher concentrations more expensive;
12. (above 100) will have more effect on (rapidly dividing) cancer cells; Explain the arrangement of phospholipids in a cell-surface membrane. - CORRECT-ANSWERSPhospholipids are arranged in a phospholipid bilayer. The hydrophobic fatty acid tails point away from the water and the hydrophilic heads attract the water.

Describe how an ester bond is formed in a phospholipid molecule. - CORRECT-ANSWERSAn ester bond is formed between a glycerol and a fatty acid, producing a water molecule in a condensation reaction. State and explain the property of water that helps to prevent temperature increase in a cell. - CORRECT-ANSWERSWater has a high specific heat capacity. This buffers changes in temperature, so lots of energy is required to change the temperature. Describe how a phagocyte destroys a pathogen present in the blood. - CORRECT-ANSWERSThe phagocyte is attracted to the pathogen by chemoattractants. The phagocyte binds to the pathogen. The pathogen is engulfed and lysosomes migrate to the phagosome. The lysosomes then release lytic enzymes which break down the pathogen. The breakdown products are then absorbed by the phagocyte. Give two types of cell, other than pathogens, that can stimulate an immune response. - CORRECT-ANSWERSCancer cells and virus infected cells. What is the role of a disulphide bridge in forming the quaternary structure of an antibody. - CORRECT-ANSWERSIt joins two polypeptide chains Outline the role of organelles in the production, transport and release of proteins from Eukaryotic cells. Do not include details of transcription or translation in your answer. - CORRECT-ANSWERSDNA in the nucleus codes for the amino acids which make up proteins. Ribosomes on the RER then synthesise these proteins. Mitochondria produce ATP for use in protein synthesis. The Golgi apparatus then packages and modifies proteins which are transported to the cell surface membrane in vesicles where they fuse. Give one advantage of viewing a biological specimen using a transmission electron microscope compared with using a scanning electron microscope. - CORRECT-ANSWERSThere is a higher resolution / view internal structures Describe and explain the mechanism that causes lungs to fill with air. - CORRECT-ANSWERSThe diaphragm muscle contracts and external intercostal muscles contract. This causes an increase in volume and decrease in pressure. This causes air to move down the pressure gradient and into the lungs. Two solutions often used to stain tissues are haematoxylin solution and iodine solution.

• Haematoxylin solution stains DNA a blue colour. • Iodine solution stains starch a blue-black colour.

The scientist used haematoxylin solution and not iodine solution to stain the lung tissue. Suggest why. - CORRECT-ANSWERSThe tissue doesn't contain starch and it makes the nucleus, which contains DNA, visible. Describe how mRNA is produced from an exposed template strand of DNA. Do not include DNA helices or splicing in your answer. - CORRECT- ANSWERSFree RNA nucleotides form complementary base pairs. RNA polymerase then forms phosphodiester bonds. Define the term exon. - CORRECT-ANSWERSA triplet base sequence which codes for a sequence of amino acids. Describe binary fission in bacteria. - CORRECT-ANSWERSCircular DNA and plasmids are replicated, tenth cytoplasm divides producing two daughter cells. Suggest and explain how two environmental variables could be changed to increase the growth rate of cells. - CORRECT-ANSWERSIncrease the concentration of glucose and oxygen to increase the rate of respiration, so growth rate increases. Increasing the temperature increases enzyme activity. Suggest and explain one advantage and one disadvantage of increased stomatal density on the growth of tobacco plant leaves. - CORRECT- ANSWERSThere is more carbon dioxide uptake therefore the rate of photosynthesis increases resulting in more growth. There is also more water loss via transpiration through the stomata, decreasing photosynthesis, slowing growth. The nucleus and a chloroplast of a plant cell both contain DNA. Give three ways in which the DNA in a chloroplast is different from DNA in the nucleus. - CORRECT-ANSWERSIn chloroplasts DNA is shorter and circular rather than linear. Introns are also absent in chloroplasts but present in DNA. Some DNA nucleotides have the organic base thymine, but RNA nucleotides do not have thymine. RNA nucleotides have uracil instead of thymine. Give one other difference between the structure of a DNA nucleotide and the structure of an RNA nucleotide. - CORRECT-ANSWERSDNA is deoxyribose and RNA is ribose. Not all mutations in the nucleotide sequence of a gene cause a change in the structure of a polypeptide. Give two reasons why. - CORRECT-ANSWERSSome triplets code for the same amino acid and also if mutations occur in introns and non-coding sequences.

What is a monoclonal antibody? - CORRECT-ANSWERSAntibodies with the same tertiary structure. Give one example of using monoclonal antibodies. - CORRECT- ANSWERSUsed in medicine to carry drugs to specific cells. Describe the role of monoclonal antibodies in producing a positive ELISA test result. - CORRECT-ANSWERSFirst the antibody binds to the complementary antigen. A second antibody with an enzyme attached to it is attached. A solution is added resulting in a colour change. A student carried out the Benedicts test. Suggest a method, other than using a colorimeter, that this student could use to measure the quantity of reducing sugar in a solution. - CORRECT-ANSWERSFilter and dry the precipitate and find a mass. Use of a colorimeter in this investigation would improve the repeatability of the student's results. - CORRECT-ANSWERSIt is quantitive rather than colour change which is qualitative therefore subjective. This standardises the method. Explain why it is more useful to calculate an index of diversity than to record species richness. - CORRECT-ANSWERSIndex of diversity also measures the abundance of each species. It is useful as there may be many of some species. Suggest how the scientist measured the rate of water flow in the river. - CORRECT-ANSWERSMeasured the movement of a floating object down river over a period of time. Use information in Table 2 and Table 3 to suggest and explain a reason for the difference in the numbers of Slate Drake mayfly at these sites in this river. - CORRECT-ANSWERSThere is less food at the site so the may flies die. It was important that the sampling procedure was standardised when collecting the Slate Drake mayflies from the two sites. Give one way in which the sampling procedure could be standardised. - CORRECT-ANSWERSTake the samples on the same day or time of day and make sure the sample area is the same size throughout. Name an organelle found in both a chloroplast and a prokaryotic cell. - CORRECT-ANSWERSRibosome

A biologist separated cell components to investigate organelle activity. She prepared a suspension of the organelles in a solution that prevented damage to the organelles. Describe three properties of this solution and explain how each property prevented damage to the organelles. - CORRECT-ANSWERSThe solution must be ice cold to reduce enzyme activity. It must be buffered to maintain the pH and stop enzymes denaturing. The solution must have the same water potential as the cell to stop the cell bursting or shrinking. Describe and explain the advantage of the counter-current principle in gas exchange across a fish gill. - CORRECT-ANSWERSWater and blood flow in opposite directions. This maintains a diffusion gradient of oxygen. Diffusion can then take place along the lamellae/filament/gill/capillary Using information from Figure 5 and Table 4, what can you conclude about the adaptation of the gas exchange surfaces of these species of fish? - CORRECT-ANSWERSThe lower the oxygen the higher the surface area to body mass and it supplies enough oxygen for respiration. Explain how the active site of enzymes causes a high rate of reaction. - CORRECT-ANSWERSIt is lowers the activation energy as induced fit causes the active site of the enzyme to denature. So the enzyme substrate complex causes bonds to break. Describe a biochemical test to confirm the presence of protein in a solution. - CORRECT-ANSWERSAdd buret reagent. A positive test will turn the solution lilac. A dipeptide consists of two amino acids joined by a peptide bond. Dipeptides may differ in the type of amino acids they contain. Describe two other ways in which all dipeptides are similar and one way in which they might differ. - CORRECT-ANSWERSThey have a COOH group at the end They have two R groups The R groups are different Name the blood vessels that carry blood to the heart muscle - CORRECT- ANSWERSCoronary arteries When HIV infects a human cell, the following events occur.

• A single-stranded length of HIV DNA is made.

• The human cell then makes a complementary strand to the HIV DNA. The complementary strand is made in the same way as a new complementary strand is made during semi-conservative replication of human DNA. Describe how the complementary strand of HIV DNA is made. - CORRECT- ANSWERSComplementary nucleotides join together via the actions of DNA Polymerase. Phosphodiester bonds form. Contrast the structures of DNA and mRNA molecules to give three differences - CORRECT-ANSWERS1. DNA double stranded/double helix and mRNA single-stranded;

2. DNA (very) long and RNA short;
3. Thymine/T in DNA and uracil/U in RNA;
4. Deoxyribose in DNA and ribose in RNA;
5. DNA has base pairing and mRNA doesn't/ DNA has hydrogen bonding and mRNA doesn't;
6. DNA has introns/non-coding sequences and mRNA doesn't; Describe the difference between the structure of a triglyceride molecule and the structure of a phospholipid molecule. - CORRECT-ANSWERSIn phospholipid, one fatty acid replaced by a phosphate Describe how you would test for the presence of a lipid in a sample of food - CORRECT-ANSWERSadd ethanol and then water. A positive test is a cloudy emulsion. Animal fats contain triglycerides with a high proportion of saturated fatty acids. If people have too much fat in their diet, absorption of the products of fat digestion can increase the risk of obesity. To help people lose weight, fat substitutes can be used to replace triglycerides in food. Describe how a saturated fatty acid is different from an unsaturated fatty acid. - CORRECT-ANSWERSthe saturated fatty acid has no double bonds This fat substitute cannot be digested in the gut by lipase. Suggest why. - CORRECT-ANSWERS1.(Fat substitute) not a complementary shape
7. Unable to fit/bind to (active site of) lipase This fat substitute is a lipid. Despite being a lipid, it cannot cross the cell- surface membranes of cells lining the gut. Suggest why it cannot cross cell- surface membranes. - CORRECT-ANSWERSIt is too big and hydrophilic Cells constantly hydrolyse ATP to provide energy. 0 3. 1 Describe how ATP is resynthesised in cells. - CORRECT-ANSWERS1. From ADP and phosphate;

2. By ATP synthase;
3. During respiration/photosynthesis; Give two ways in which the hydrolysis of ATP is used in cells. - CORRECT- ANSWERSProvides energy for photosynthesis and respiration and adds a phosphate to substances making them more reactive and changing their shape. What is the evidence from Figure 2 that a scanning electron microscope was used to take this photograph? - CORRECT-ANSWERSthe image is 3D Y is a protein. One function of Y is to transport cellulose molecules across the phospholipid bilayer. Using information from Figure 3, describe the other function of Y. - CORRECT-ANSWERS1.(Y is) an enzyme/has active site/forms ES complex;
4. That makes cellulose/attaches substrate to cellulose/joins β glucose; OR
5. Makes cellulose/forms glycosidic bonds;
6. From β glucose; What is the evidence in Figure 3 that the phospholipid bilayer shown is part of the cell-surface membrane? - CORRECT-ANSWERSCell wall forms outside cell-surface membrane/has cellulose on it Scientists investigated the hydrolysis of sucrose in growing plant cells by an enzyme called SPS. 0 5. 1 Name the products of the hydrolysis of sucrose - CORRECT-ANSWERSGlucose and fructose Describe the induced-fit model of enzyme action. - CORRECT-ANSWERS1. (before reaction) active site not complementary to/does not fit substrate;
7. Shape of active site changes as substrate binds/as enzymesubstrate complex forms;
8. Stressing/distorting/bending bonds (in substrate leading to reaction) A quantitative Benedict's test produces a colour whose intensity depends on the concentration of reducing sugar in a solution. A colorimeter can be used to measure the intensity of this colour. The scientist used quantitative Benedict's tests to produce a calibration curve of colorimeter reading against concentration of maltose. Describe how the scientist would have produced the calibration curve and used it to obtain the results in Figure 4.

Do not include details of how to perform a Benedict's test in your answer - CORRECT-ANSWERS1. Make/use maltose solutions of known/different concentrations (and carry out quantitative Benedict's test on each);

2. (Use colorimeter to) measure colour/colorimeter value of each solution and plot calibration curve/graph described;
3. Find concentration of sample from calibration curve