Spec 2 Set 1

Question 1

“Push down hard on the cover slip, but do not push the cover slip sideways.”

Explain why she was given this instruction.

Answer 1

1. Push hard – spread/squash tissue;

2. Not push sideways – avoid rolling cells together/breaking chromosomes;

Question 2

The scientist concluded that the cells in flask G took up sodium ions by active transport. Explain how the information given supports this conclusion.

Answer 2

1. Uptake in flask G much greater than in flask F;
2. Showing use of ATP in flask G;
3. Sodium ion concentration in flask G falls to zero;
4. Showing uptake against a concentration gradient;

Question 3

The curve for flask F levelled off after 20 minutes. Explain why.

Answer 3

(Uptake of sodium ions occurring by) facilitated diffusion;

Equilibrium reached/sodium ion concentrations in solution and in cells the same;

Question 4

Figure 3 represents one process that occurs during protein synthesis.

Name the process shown.

Answer 4

Translation

Question 5

Molecule used in translation.

Answer 5

Translation RNA

Question 6

Describe how two amino acids differ from one another.

Answer 6

Have different R group

Question 7

Deletion of the sixth base (G) in the sequence shown in Figure 3 would change the nature of the protein produced but substitution of the same base would not. Explain why.

Answer 7

Substitution would result in CCA/CCC/CCU;
(All) code for same amino acid/proline;
Deletion would cause frame shift/change in all following codons/change next codon from UAC to ACC

Question 8

Describe and explain the mechanism that causes forced expiration.

Answer 8

1. Contraction of internal intercostal muscles;
2. Relaxation of diaphragm muscles/of external intercostal muscles;
3. Causes decrease in volume of chest/thoracic cavity;
4. Air pushed down pressure gradient;

Question 9

The people in group B were recovering from an asthma attack.

Explain how an asthma attack caused the drop in the mean FEV shown in Figure 4.

Answer 9

1. Muscle walls of bronchi/bronchioles contract;
2. Walls of bronchi/bronchioles secrete more mucus;
3. Diameter of airways reduced;
4. (Therefore) flow of air reduced;

Question 10

The scientists used kittens (newborn cats) as model organisms in their laboratory investigation.
Other than ethical reasons, suggest two reasons why they chose to use cats as model organisms.

Answer 10

1. (Are mammals so) likely to have same physiology/reactions as humans;
2. Small enough to keep in laboratory / produce enough milk to extract;

Question 11

Explain why monitoring the pH of the mixture could show whether the cat’s milk contained lipase.

Answer 11

1. Hydrolysis of lipids produces fatty acids;

2. Which lower pH of mixture;

Question 12

What can you conclude from Figure 5 about the importance of bile-activated lipase in breast milk?

Answer 12

1. (Bile-activated lipase/it) increases growth rate (of kittens);
2. Results for formula with lipase not (significantly) different from breast milk/are (significantly) different from formula milk alone;
3. Showing addition of (bile-activated) lipase is the likely cause (of increased growth);
4. Lipase increases rate of digestion of lipids/absorption of fatty acids;

Question 13

Suggest how this student would obtain data to give a more precise value for the index of diversity of this habitat.

Answer 13

1. Take more samples and find mean;

2. Random sampling using quadrats

Question 14

Can you conclude that the insect pest resistant to Bt toxin found in the years 2002 to 2005 was the same insect species? Explain your answer.

Answer 14

bar chart only shows number of species, not the name of the species

Question 15

One farmer stated that the increase in the use of Bt crop plants had caused a mutation in one of the insect species and that this mutation had spread to other species of insect.
Was he correct? Explain your answer.

Answer 15

(No – no mark)

1. Mutations are spontaneous/random;
2. Only the rate of mutation is affected by environment;
3. Different species do not interbreed/do not produce fertile offspring;
4. So mutation/gene/allele cannot be passed from one species to another;

Question 16

There was a time lag between the introduction of Bt crops and the appearance of the first insect species that was resistant to the Bt toxin.
Explain why there was a time lag.

Answer 16

1. Initially one/few insects with favourable mutation/allele;
2. Individuals with (favourable) mutation/allele will have more offspring;
3. Takes many generations for (favourable) mutation/allele to become the most common allele (of this gene);

Question 17

Explain why antibody A attaches only to the protein found in species of Plasmodium.

Answer 17

1. Antibody has tertiary structure;

2. Complementary to binding site on protein;

Question 18

Antibody B is important if this test shows a person is not infected with Plasmodium.

Explain why antibody B is important.

Answer 18

1. Prevents false negative results;

2. (Since) shows antibody A has moved up strip/has not bound to any Plasmodium protein;

Question 19

One of these test strips was used to test a sample from a person thought to be infected with Plasmodium. Figure 8 shows the result.
What can you conclude from this result?
Explain how you reached your conclusion.

Answer 19

1. Person is infected with Plasmodium/has malaria;
2. Infected with (Plasmodium) vivax;
3. Coloured dye where antibody C present;
4. That only binds to protein from vivax/no reaction with antibody for falciparum;

Question 20

Describe how a high pressure is produced in the leaves.

Answer 20

1. Water potential becomes lower/becomes more negative (as sugar enters phloem);
2. Water enters phloem by osmosis;
3. Increased volume (of water) causes increased pressure;

Question 21

During their experiment, the scientists ensured that the rate of photosynthesis of their plants remained constant.
Explain why this was important.

Answer 21

1. Rate of photosynthesis related to rate of sucrose production;
2. Rate of translocation higher when sucrose concentration is higher;

Question 22

The scientists concluded that some translocation must occur in the spaces in the cell walls.
Explain how the information in Figure 9 supports this conclusion.

Answer 22

1. Rate of translocation does not fall to zero /
   translocation still occurs after 120 minutes;
2. But sucrose no longer able to enter cytoplasm
   of phloem cells;

Question 23

When a vaccine is given to a person, it leads to the production of antibodies against a disease-causing organism.
Describe how.

Answer 23

1. Vaccine contains antigen from pathogen;
2. Macrophage presents antigen on its surface;
3. T cell with complementary receptor protein binds to antigen;
4. T cell stimulates B cell;
5. (With) complementary antibody on its surface;
6. B cell secretes large amounts of antibody;
7. B cell divides to form clone all secreting/producing same antibody;

Question 24

Describe the difference between active and passive immunity.

Answer 24

1. Active involves memory cells, passive does not;
2. Active involves production of antibody by plasma cells/memory cells;
3. Passive involves antibody introduced into body from outside/named source;
4. Active long term, because antibody produced in response to antigen;
5. Passive short term, because antibody (given) is broken down;
6. Active (can) take time to develop/work, passive fast acting;