AS Biology Specimen question paper Paper 1

Question 1

A technician investigated the effect of temperature on the rate of an enzyme-controlled
reaction. At each temperature, he started the reaction using the same volume of
substrate solution and the same volume of enzyme solution.
Figure 2 shows his results.
Give one other factor the technician would have controlled.

Answer 1

Concentration of substrate solution / of enzyme
solution / pH;

Question 2

Describe and explain the differences between the two curves.

Answer 2

1. Initial rate of reaction faster at 37 °C;
2. Because more kinetic energy;
3. So more E–S collisions/more E–S complexes
   formed;
4. Graph reaches plateau at 37 °C;
5. Because all substrate used up;

Question 3

Describe and explain the appearance of one of the chromosomes in cell X.

Answer 3

1. Chromosome is formed of two chromatids;
2. (Because) DNA replication (has occurred);
3. (Sister) chromatids held together by
   centromere;

Question 4

Describe and explain the appearance of one of the chromosomes in cell X.

Answer 4

1. Chromosomes in homologous pair;
2. One of each into daughter cells / haploid
   number;

Question 5

Identify one event that occurred during division 2 but not during division 1.

Answer 5

Separation of (sister) chromatids / division of
centromere;

Question 6

Name two ways in which meiosis produces genetic variation.

Answer 6

1. Independent segregation (of homologous
   chromosomes);
2. Crossing over / formation of chiasmata;

Question 7

Name part F of each nucleotide.

Answer 7

Deoxyribose sugar

Question 8

The arrows in Figure 5 show the directions in which each new DNA strand is being
produced.
Use Figure 4, Figure 5 and your knowledge of enzyme action to explain why the
arrows point in opposite directions.

Answer 8

(Figure 4 shows) DNA has antiparallel
strands/described;
2. (Figure 4 shows) shape of the nucleotides is different and nucleotides aligned differently;
3. Enzymes have active sites with specific shape;
4. Only substrates with complementary
shape to the 3’ end can bind with active site of enzyme/active site of DNA polymerase

Question 9

Describe how you would test a piece of food for the presence of lipid.

Answer 9

Dissolve in alcohol, then add water;
2. White emulsion shows presence of lipid;

Question 10

Name the type of bond between A and fatty acid X.

Answer 10

Ester

Question 11

Which of the fatty acids, X or Y, in Figure 8 is unsaturated? Explain your answer

Answer 11

Y (no mark)
Contains double bond between (adjacent) carbon
atoms in hydrocarbon chain

Question 12

The scientists expressed their results as Percentage of lipid in plasma membrane
by mass. Explain how they would find these values.

Answer 12

Divide mass of each lipid by total mass of all
lipids (in that type of cell);
2. Multiply answer by 100;

Question 13

Cholesterol increases the stability of plasma membranes. Cholesterol does this by
making membranes less flexible.
Suggest one advantage of the different percentage of cholesterol in red blood cells
compared with cells lining the ileum.

Answer 13

Red blood cells free in blood/not supported by
other cells so cholesterol helps to maintain shape;
1

Question 14

E. coli has no cholesterol in its cell-surface membrane. Despite this, the cell maintains
a constant shape. Explain why

Answer 14

1. Cell unable to change shape;
2. (Because) cell has a cell wall;
3. (Wall is) rigid/made of peptidoglycan/murein;