Draw a labelled diagram of the ultrastructure of Escherichia coli as an example of a prokaryote.

Describe the events that occur in the four phases of mitosis in animals.

Explain the process of aerobic cell respiration after glycolysis has occurred.

Award [1] for each structure clearly drawn and correctly labelled.

a. cell wall; (with some thickness)

b. plasma membrane; (shown as single line or very thin)

c. cytoplasm;

d. pilus/pili; (shown as single lines)

e. flagellum/flagella; (shown as thicker and longer structures than pili and embedded in cell wall)

f. 70S ribosomes;

g. nucleoid / naked DNA;

h. approximate width 0.5μm / approximate length 2.0μm;

Award [4 max] if the bacterium drawn does not have the shape of a bacillum (rounded-corner rectangle with length approximately twice its width).

Award [4 max] if any eukaryotic structures included.

Accept the following points as a diagram if clearly drawn and correctly labelled.

a. supercoiling of chromosomes in prophase;

b. chromosomes consist of sister chromatids in prophase;

c. formation of mitotic spindle / centrosomes/centrioles move away in prophase;

d. nuclear membrane breaks down in (late) prophase/(early) metaphase;

e. attachment of spindle microtubules to centromeres;

f. chromosomes on metaphase plate/equator/centre of cell in metaphase;

g. parting of (sister) chromatids at onset of anaphase;

h. movement of sister chromosomes (accept chromatids) to opposite poles in anaphase;

i. re-formation of nuclear membranes in telophase;

Award [5 max] if response does not mention all four phases of mitosis.

a. pyruvate produced by glycolysis;

b. pyruvate enters mitochondrion/mitochondria;

c. pyruvate loses CO₂ in link reaction;

d. and NADH+H⁺;

e. with formation of acetyl CoA;

f. to take part in Krebs cycle;

g. where two CO₂ are produced (per molecule of pyruvate);

h. one ATP from ADP+Pi;

i. along with (three) NADH+H⁺ (and one FADH₂);

j. NADH+H⁺ provide electrons circulating in the electron transport chain on the inner mitochondrial membrane;

k. allowing H⁺ to accumulate in the intermembrane space;

l. and come back to the matrix through ATP synthase/synthetase to produce ATP (by chemiosmosis);

m. presence of O₂ required as the final electron acceptor for the electron transport chain;

n. producing water with H⁺;

Many candidates automatically lost points for not showing the bacillus shape and/or including eukaryotic organelles. Diagrams are meant to be an accurate representation of the organism. Pilli and flagellae floating around outside the cell, not even touching the cell wall did not gain marks.

The process of mitosis was well known by the majority of candidates answering this question. Common errors were pairing the homologous chromosomes and explaining meiosis rather than mitosis. Many candidates included neat labelled diagrams for which marks could be awarded.

Many candidates were able to describe the link reaction, Krebs cycle, electron transport and chemiosmosis with almost textbook precision. Others tried to draw half remembered diagrams, hoping for the best and not scoring many, if any, marks.