AS Biology Paper 1 2017

04 . 2) Use Figure 3 to calculate the volume of blood pumped per minute by the left ventricle. [2 marks]

(Acceptable range is) 6315.79 to 6400;;

08 . 4) Explain the result for the chip in 0.8 mol dm-3 sucrose solution. [2 marks]

1. (0.8 mol dm-3 sucrose) solution has a more negative / lower water potential than potato (cytoplasm); OR potato (cytoplasm) has a less negative / higher water potential than (0.8 mol dm-3 sucrose) solution; 2. (therefore) water moves out (of potato) into the (sucrose) solution by osmosis (so cells decrease in mass);

10 . 3) Suggest why high doses of AZT lead to muscle wastage (lines 10-11). [2 marks]

1. (Fewer mitochondria so) less (aerobic) respiration; 2. (Muscles receive) less ATP (so waste);

02 . 3) The student concluded that the minimum concentration of propan-2-ol needed to stop the growth of Lactobacillus was 15 units. This conclusion is incorrect. Describe how you could obtain a more accurate estimate of the minimum concentration of propan-2-ol needed to stop the growth of this species of bacterium. [2 marks]

1. (Several) values between 10 and 15 (units); 2. Repetitions of each;

01 . 4) Adenosine triphosphate (ATP) is a nucleotide derivative. Contrast the structures of ATP and a nucleotide found in DNA to give two differences. [2 marks]

1. ATP has ribose and DNA nucleotide has deoxyribose; 2. ATP has 3 phosphate (groups) and DNA nucleotide has 1 phosphate (group); 3. ATP- base always adenine and in DNA nucleotide base can be different / varies;

08 . 3) Calculate the ratio of final mass to initial mass of potato chips and plot a suitable graph of your processed data. Express the ratios in Table 4 as a single number (for example 5.26:1 would be expressed as 5.26). [3 marks]

1. Axes correct way round with linear scales; 2. Axes labelled with mol dm-3 and ratio without units; 3. Correct values correctly plotted and suitable curve drawn;

01 . 3) The enzymes DNA helicase and DNA polymerase are involved in DNA replication. Describe the function of each of these enzymes. [2 marks]

1. DNA helicase - (unwinding DNA and) breaking hydrogen bonds / bonds between chains / bases / strands; 2. DNA polymerase - joins (adjacent) nucleotides OR forms phosphodiester bond / sugarphosphate backbone;

03 . 2) Explain the advantages of lipid droplet and micelle formation. [3 marks]

1. Droplets increase surface areas (for lipase / enzyme action); 2. (So) faster hydrolysis / digestion (of triglycerides / lipids); 3. Micelles carry fatty acids and glycerol / monoglycerides to / through membrane / to (intestinal epithelial) cell;

03 . 3) Name structure Q in Figure 2 and suggest how it is involved in the absorption of lipids. [4 marks]

1. Golgi (apparatus); 2. Modifies / processes triglycerides; 3. Combines triglycerides with proteins; 4. Packaged for release / exocytosis OR Forms vesicles;

06 . 4) Crossing over greatly increases genetic diversity in this species of moss. Describe the process of crossing over and explain how it increases genetic diversity. [4 marks]

1. Homologous pairs of chromosomes associate / form a bivalent; 2. Chiasma(ta) form; 3. (Equal) lengths of (non-sister) chromatids / alleles are exchanged; 4. Producing new combinations of alleles;

07 . 1) Crossing over greatly increases genetic diversity in this species of moss. Describe the process of crossing over and explain how it increases genetic diversity. [4 marks]

1. Macerate / homogenise / blend / break tissues / cells (in solution); 2. Centrifuge; 3. At different / increasing speeds until chloroplast fraction obtained;

09 . 3) 68% of all the fish caught in this investigation came from sample A. A student thought this showed that sample A had a greater index of diversity than any of the other samples. It is not possible to draw this conclusion from the given data. Give reasons why. [3 marks]

1. Number of individuals of each species not known; 2. Almost all (of sample A / the 68%) could be of the same species; 3. Two / other samples have a higher number of species / higher species richness but a lower number of individuals / fish; 4. Other samples may have more individuals of each species;

10 . 1) Read the following passage. Azidothymidine (AZT) is a drug used to treat people infected with human immunodeficiency virus (HIV). It inhibits the enzyme that synthesises DNA from HIV RNA. This does not destroy HIV in the body but stops or slows the development of AIDS. In the past, some people who took AZT on its own eventually developed AIDS. Some of the HIV in their bodies had become resistant to AZT. To prevent this from happening, people infected with HIV are now treated with highly active antiretroviral therapy (HAART). This involves taking AZT with other anti-HIV drugs at the same time. AZT is taken in low doses. This is because people who took high doses over long periods of time suffered muscle wastage. It was found that high doses of AZT inhibit replication of mitochondria. Use information from the passage and your own knowledge to answer the questions. Suggest and explain why AZT does not destroy HIV in the body but stops or slows the development of AIDS (lines 3-4). [4 marks]

1. Person (infected with HIV) has HIV DNA (in their DNA); 2. New HIV (particles) still made; 3. (AZT) inhibits reverse transcriptase; 4. (AZT) stops these (new HIV particles) from forming new HIV DNA; OR Slows / stops replication of HIV; 5. Stops destruction of more / newly infected T cells; 6. So immune system continues to work (and AIDS does not develop);

10 . 2) Suggest and explain two advantages of using HAART (lines 7-9). [4 marks]

1. Slows / stops the development of AIDS; 2. Because HIV resistant to AZT is damaged / destroyed / prevented from replicating (by other drugs); OR 3. AZT continues to work as a drug; 4. Because HAART prevents the spread of AZT-resistant HIV to rest of the human population; OR 5. No new HIV particles made; 6. Because HAART might interfere with viral protein synthesis;

02 . 1) A student investigated the effect of three types of disinfectant on the growth of Lactobacillus bacteria. During the investigation, the student: • boiled the agar before pouring the agar plates • transferred 0.5 cm3 of a diluted liquid culture of Lactobacillus onto each agar plate • left some agar plates as controls • added to other agar plates different concentrations of the disinfectants as shown in Table 1 on page 5. After 2 days, she counted the number of colonies of bacteria on each agar plate. Explain the purpose of: [2 marks]

1. So no contamination/ other bacteria; 2. So same number of bacteria transferred to allow comparison;

09 . 1) Define each of the following terms. [2 marks]

1. Species = (A group of) organisms that are able to produce fertile offspring; 2. Species richness = the number of (different) species in a community;

07 . 4) Scientists investigated the effect of an exercise programme on the number and size of mitochondria in skeletal muscle. They took samples of muscle from a large number of volunteers before and after the exercise programme. From each sample, they cut thin sections and used these to determine the mean number of mitochondria per μm2 and the mean area of inner mitochondrial membranes. Their results are shown in Figure 7 and Figure 8. What do the data in Figure 7 and Figure 8 suggest about the effect of the exercise programme on mitochondria? [2 marks]

1. Training made no difference to number (of mitochondria per μm 2 ); 2. Training led to an increase in the area (of inner mitochondrial membrane);

06 . 2) Explain how the chromosome number is halved during meiosis. [2 marks]

2 1. Homologous chromosomes (pair); 2. One of each (pair) goes to each (daughter) cell / to opposite poles;

02 . 2) The three disinfectants used by the student were Lysol, propan-2-ol and ammonia. Table 1 shows the student's results The liquid culture the student transferred was diluted by 1 in 10 000 (10-4 ). Use information in this question to calculate how many bacteria were present in 1 cm3 of undiluted liquid culture. [2 marks]

2 6 000 000 OR 6 × 106 ;;

04. 3) Explain the role of the heart in the formation of tissue fluid. [2 marks]

3 1. Contraction of ventricle(s) produces high blood / hydrostatic pressure; 2. (This) forces water (and some dissolved substances) out (of blood capillaries);

09 . 2) Scientists investigated the species richness of fish caught at various depths in the Pacific Ocean close to the western coast of Chile. Figure 9 shows the scientists' results. 68% of all the fish caught in this investigation came from sample A. What is the modal value of species richness? [1 mark]

5;

06 . 3) Figure 6 shows a cell from the moss plant. The cell is in the second meiotic division What is the haploid number of chromosomes for this species of moss? [1 mark]

6;

01 . 1) Figure 1 shows part of a DNA molecule. How many nucleotides are shown in Figure 1? [1 mark]

8;

08 . 1) Give three properties of water that are important in biology. [3 marks]

Accept any three suitable properties e.g.: Is a metabolite Is a solvent Has a (relatively) high heat capacity Has a (relatively) large latent heat of vaporisation / evaporation Has cohesion / hydrogen bonds between molecules;;;

05 . 1) Scientists measured the mean amino acid concentration in white wines made from grapes grown organically and white wines made from grapes that were not grown organically. Which test could the scientists have used to identify that there are amino acids in white wine? [1 mark]

Biuret;

05 . 4) The scientists used a statistical test to determine whether there was a significant difference in the amino acid concentration in the two types of white wine. They obtained a value for P of 0.04. Name the statistical test the scientists used and give a reason for your answer. Was the difference significant? Give a reason for your answer. [3 marks]

Choice: (Student's) t-test; Reason for choice: Looking for differences between two means; Explanation: Difference is significant / not due to chance because the P value is 0.04 / is less than 0.05;

06 . 1) Figure 5 shows the life cycle of a moss plant. In this life cycle, only the stalk and spore capsule are diploid. All the cells in all the other stages of the life cycle of the moss are haploid. Which letter, A, B, C or D, in Figure 5, shows where meiosis occurs in the life cycle of the moss? Write the appropriate letter in the box provided. [1 mark]

D;

03 . 1) Tick () the box by the name of the process by which fatty acids and glycerol enter the intestinal epithelial cell. [1 mark]

Diffusion

08 . 2) A student investigated the effect of different concentrations of sucrose solution on "chips" cut from a potato. Each chip had the same dimensions. The student: • weighed each chip at the start • placed each chip in a separate test tube, each containing 10 cm3 of sucrose solution at a different concentration • left the chips in the sucrose solution for 24 hours • dried the surface of the chips and then weighed them again. Table 4 shows the student's results. The student produced the sucrose solutions with different concentrations from a concentrated sucrose solution. Name the method she would have used to produce these sucrose solutions. [1 mark]

Dilution series;

05 . 2) All amino acids have the same general structure. Figure 4 shows the structure of the amino acid isoleucine. Draw a box around the part of the molecule that would be the same in all amino acids. [1 mark]

Draw around H2N - C - COOH; H

04 . 4) Lymphoedema is a swelling in the legs which may be caused by a blockage in the lymphatic system. Suggest how a blockage in the lymphatic system could cause lymphoedema. [1 mark]

Excess tissue fluid cannot be (re)absorbed / builds up;

05 . 3) Name the chemical element found in all amino acids that is not found in triglycerides. [1 mark]

Nitrogen;

01 . 2) Name the type of bond labelled X in Figure 1. [1 mark]

Phosphodiester (bond);

04 . 1) Figure 3 shows the volume changes in the left ventricle of a human heart during two cardiac cycles. The numbers 1, 2, 3 and 4 represent times when heart valves open or close. Use information from Figure 3 to complete Table 2. Place the number 1, 2, 3 or 4 in the appropriate box. [2 marks]

Semi-lunar valves 2 3 Atrioventricular valves 4 1

07 . 3) Give the function of a mitochondrion. [1 mark]

The site of aerobic respiration (reactions) OR ATP is made / ADP is phosphorylated;