Draw a labelled diagram of the ultrastructure of a prokaryote.

Explain the process of DNA replication.

Outline how the structure of the ribosome is related to its function in translation.

Award any of the following clearly drawn and correctly labelled.
cell wall; (shown as a double line)
plasma membrane; (less than the width of wall) (reject inner surface of cell wall labelled as cell membrane)
nucleoid/(region containing) naked DNA (distinguished from rest of cytoplasm)
ribosome; (dots in cytoplasm)
cytoplasm;
flagella; (at least a quarter as long as the cell)
pili; (less than a quarter as long as the cell)
Award [3 max] if any specifically eukaryotic structure shown.

helicase uncoils DNA/splits DNA into two strands;
(RNA) primase adds short length of RNA/primer;
primer allows attachment of (DNA) polymerase;
DNA polymerase III copies DNA;
adds nucleotides in the 5′ to 3′ direction;
uses deoxynucleoside triphosphates/nucleotides that are free in cell;
two phosphates removed to release energy (required for the process);
(complementary base pairing of) adenine with thymine and guanine with cytosine; (reject A with T and C with G)
(leading) strand replication towards the replication fork;
short pieces of daughter DNA / Okazaki fragments (on lagging strand);
DNA polymerase I removes the RNA primers/replaces them with DNA;
(DNA) ligase joins short fragments/seals nicks;
by making sugar-phosphate bond;

translation is protein/polypeptide synthesis;
formed by (ribosomal) RNA and proteins; (both needed)
about 20nm/30nm / 80S in eukaryotes;
organized into a tertiary structure/globular shape;
a small subunit and a large one;
(three) binding sites for tRNA on/in large subunit;
A, P and E sites;
binding site for mRNA on surface/in small subunit;
two tRNA can bind at the same time;
ribosomal RNA catalyses formation of peptide bond;

In part (a), most candidates drew an appropriate diagram of a prokaryote cell and there was a continuation of the improvement in the quality of diagrams that has been seen over recent years. In a few cases, eukaryote structures such as mitochondria had been included. Pili and flagella were not always distinguishable.

Replication is a complicated process and candidates were expected to be able to describe it in detail in (b). The strongest candidates did this admirably well, but weaker ones tended to reveal misunderstandings or gaps in knowledge. It is usually possible for examiners to distinguish between those who have developed a genuine understanding and others who may have memorized some key phrases but are unable to use them correctly in context.

The emphasis in the answer to part (c) of the question needed to be on ribosome structure, rather than the process of translation. There were some detailed descriptions of translation that made only passing reference to structure and so scored poorly. Diagrams were often included but they needed to be annotated fully to gain marks for a particular idea. Some of the best answers included the idea that ribosomes are composed of both protein and ribosomal RNA, with the RNA having a catalytic role in translation.