AS Biology Paper 1 Mark Scheme Questions

Question 1

Name the molecule, other than a dipeptide, formed when two molecules of glycine are joined together.

Answer 1

Water.

Question 2

Name the part of the DNA nucleotide which contains phosphorus.

Answer 2

ADP.

Question 3

What is meant by the term tertiary structure?

Answer 3

It is the final 3D structure of a protein. The protein has been coiled or folded further due to interactions between the R groups.

Question 4

Suggest why a stretched protein with disulfide bonds takes less time to refold than a protein without disulfide bonds.

Answer 4

Disulfide bonds reduce the amount of unfolding of the protein.

Question 5

Give two properties of water that are important in the cytoplasm of cells. For each property of water, explain its importance in the cytoplasm.

Answer 5

Property 1- important solvent
Importance- metabolic reactions will occur faster in solution.

Property 2- polar
Importance- acts as a universal solvent so metabolic reactions are faster.

Question 6

Compare and contrast the processes by which water and inorganic ions enter cells.

Answer 6

Both move down concentration gradient.
Both move through protein channels in membrane.
Ions can move against a concentration gradient by active transport.

Question 7

Galactose has a similar structure to part of the lactose molecule.
Explain how galactose inhibits lactase.

Answer 7

Galactose is a competitive inhibitor so it attaches to the active site of lactase. Therefore fewer enzyme-substrate complexes are formed.

Question 8

Describe how the complementary strand of HIV DNA is made when made the same way as a new complementary strand is made during semi-conservative replication of human DNA.

Answer 8

Complementary bases pair.
Condensation reaction join the nucleotides of the new strand together — catalysed by the DNA polymerase