Thursday 25 May 2017

Question 1

Name the bond between the phosphate and sugar?

Answer 1

Phosphodiester bond

Question 2

DNA helicase

Answer 2

• (unwinding DNA and) breaking hydrogen bonds

Question 3

DNA polymerase

Answer 3

• joins (adjacent) nucleotides

- forms phosphodiester bond / sugar- phosphate backbone;

Question 4

Contrast the structures of ATP and a nucleotide found in DNA to give two differences.

Answer 4

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;

Question 5

Explain the purpose of: boiling the agar

Answer 5

So no contamination/ other bacteria;

Question 6

Transferring the same volume of liquid culture onto each agar plate.

Answer 6

So same number of bacteria transferred to allow comparison;

Question 7

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.

Answer 7

• Take several values between 10 and 15 units

- Repeat each

Question 8

Process by which fatty acids and glycerol enter the intestinal epithelial cell.

Answer 8

Diffusion

Question 9

Explain the advantages of lipid droplet and micelle formation. 3 marks

Answer 9

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;

Question 10

How is the Golgi involved in the absorption of lipids?

Answer 10

• Modifies triglycerides
• Combines trigylcerides to proteins
• Forms vesicles

Question 11

Explain the role of the heart in the formation of tissue fluid.

Answer 11

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

Question 12

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.

Answer 12

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

Question 13

Which test could the scientists have used to identify that there are amino acids in white wine?

Answer 13

Biuret

Question 14

Draw a box around the part of the molecule that would be the same in all amino acids.

Answer 14

H2N – C – COOH; H

Question 15

Name the chemical element found in all amino acids that is not found in triglycerides.

Answer 15

Nitrogen

Question 16

Explain how the chromosome number is halved during meiosis.

Answer 16

1. Homologous chromosomes (pair);

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

Question 17

What is the haploid number of chromosomes for this species of moss?

Answer 17

6

Question 18

Describe the process of crossing over and explain how it increases genetic diversity.

Answer 18

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;

Question 19

Describe how you would use cell fractionation techniques to obtain a sample of chloroplasts from leaf tissue. Do not include in your answer information about any solutions.

Answer 19

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

Question 20

Give the function of a mitochondrion.

Answer 20

The site of aerobic respiration (reactions) OR

ATP is made / ADP is phosphorylated;

Question 21

Give three properties of water that are important in biology.

Answer 21

 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;;;

Question 22

Name the method she would have used to produce these sucrose solutions.

Answer 22

Dilution series;

Question 23

0.8; 2.72 - 2.20

Explain the result for the chip in 0.8 mol dm–3 sucrose solution.

Answer 23

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);

Question 24

Species

Answer 24

organisms that are able to produce fertile offspring

Question 25

Species richness

Answer 25

the number of (different) species in a community;

Question 26

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.

Answer 26

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;

Question 27

Suggest and explain why AZT does not destroy HIV in the body but stops or slows the development of AIDS (lines 3–4).

Answer 27

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);

Question 28

Suggest and explain two advantages of using HAART (lines 7–9)

Answer 28

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;

Question 29

Suggest why high doses of AZT lead to muscle wastage (lines 10–11).

Answer 29

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