Date | November 2015 | Marks available | 4 | Reference code | 15N.3.SL.TZ0.9 |
Level | Standard level | Paper | Paper 3 | Time zone | TZ0 |
Command term | Explain | Question number | 9 | Adapted from | N/A |
Question
Draw a labelled diagram showing the structure of a chloroplast.
Explain how energy is released and used to make ATP by electron carriers in the electron transport chain during aerobic respiration.
Markscheme
Award [1] for each of the following clearly drawn and correctly labelled.
a. outer and inner membranes;
b. stroma;
c. thylakoid;
d. granum;
e. (70S) ribosomes / (naked) DNA;
f. starch granules;
a. electron carriers found on inner membrane/cristae of mitochondria;
b. H/H+/protons transported to electron carriers by NAD and FAD;
c. series of redox reactions in membrane;
d. electrons are passed down energy gradient;
e. establishes proton gradient / protons accumulate (in intermembrane space);
f. oxygen is the final electron acceptor;
g. generation of ATP through chemiosmosis;
Accept correct answers in an annotated diagram.
Examiners report
There was a range of diagrams of the chloroplast with the many achieving all 3 marks.
The electron transport chain was not well understood. Many candidates assumed it referred to the chloroplast from part (a).