June 2021 Paper 1

Question 1

Describe the process of glycolysis.

Answer 1

1. Phosphorylation of glucose using ATP;
2. Oxidation of triose phosphate to pyruvate;
3. Net gain of ATP;
4. NAD reduced;

Question 2

Malonate inhibits a reaction in the Krebs cycle.
Explain why malonate would decrease the uptake of oxygen in a respiring cell

Answer 2

Less/no reduced NAD/coenzymes
-Oxygen is the final/terminal (electron) acceptor;

Question 3

Describe and explain how the polymerase chain reaction (PCR) is used to amplify a DNA fragment

Answer 3

-requires DNA/Taq polymerase, nucleotides and primers
-DNA heated to 95 degrees which breaks the hydrogen bonds
-decrease temp to 50 degrees so primers can anneal
-polymerase binds nucleotides together

Question 4

Why would PCR stop/plateau (on a graph)

Answer 4

-no more nucleotides left