Outline the stages of the cell cycle.

Explain the process of translation in cells.

Outline the production of a dipeptide by a condensation reaction, showing the structure of a generalized dipeptide.

a. interphase is the longest phase;

b. interphase includes G₁, S and G₂;

c. in G₁ and G₂ /G phases, cell performs normal functions/protein synthesis/cell grows/organelles are replicated;

d. S/synthesis phase when the DNA replicates;

e. mitosis is when nucleus/genetic material divides;

f. named/described stages of mitosis;

g. cytokinesis: the division of the cytoplasm / formation of two daughter cells;

Award [3 max] if all three stages (interphase, mitosis and cytokinesis) are not mentioned.

a. translation is the conversion of base sequence on mRNA into an amino acid sequence / OWTTE;

b. messenger/mRNA attaches to ribosome (small unit);

c. many ribosome/polyribosomes bind to same mRNA;

d. (mRNA) carries codons/triplet of bases each coding for one amino acid;

e. transfer/tRNA each have specific anticodon;

f. tRNA carries specific amino acid;

g. tRNA anticodon binds to codon in the mRNA;

h. to corresponding triplet base/codon by complementary base pairing / OWTTE;

i. a second tRNA (anticodon) binds to next codon;

j. two amino acids bind together / peptide linkage is formed;

k. first tRNA detaches;

l. ribosome moves along mRNA;

m. another tRNA binds to next codon;

n. continues until stop codon is reached;

o. stop codon has no corresponding tRNA (anticodon)/amino acid/causes release of polypeptide;

a. condensation is joining together two amino acids to form a dipeptide;

b. carboxyl/COOH group of one amino acid reacts with amine/NH₂ group of another / diagrams of two (generalized) amino acids correctly shown;

c. water/H₂O is eliminated;

d. diagram of dipeptide correctly shown;

e. peptide/covalent bond is produced / peptide bond correctly labelled;

f. occurs at the ribosomes;

Few managed to state that mitosis is the division of the nucleus/ genetic material and also lumped in cytokinesis as a part of mitosis.

Better candidates were able to explain the process of translation in very clear detail. It was good to see that very few candidates confused transcription and translation.

Most gained the mark for stating that water is eliminated in a condensation reaction. Unfortunately they could not explain the process in sufficient detail to gain any more marks. Even although the stem was about dipeptides, weaker candidates wrote about carbohydrates. There were some G2 comments that asking SL candidates to draw a dipeptide was beyond expectations. It is indeed on the limit of what could be expected from 3.2.2 and 3.2.5. However the candidates did have a choice of Section B questions.