SAJC_2010_H2-Bio-TYS-ANS

2010 UCLES ‘A’ Level H2 Biology Mark Scheme 1 2010 ‘A’ Level H2 Biology Mark Scheme PAPER 1 (MCQ) 1 C 21 C 2 A 22 C 3 C 23 B 4 C 24 D 5 D 25 C 6 D 26 D 7 C 27 C 8 D 28 B 9 C 29 C 10 B 30 C 11 B 31 A 12 A 32 D 13 A 33 B 14 B 34 B 15 C 35 D 16 D 36 A 17 D 37 A 18 B 38 B 19 D 39 B 20 B 40 D

2010 UCLES ‘A’ Level H2 Biology Mark Scheme 2 PAPER 2 (CORE) QUESTION 1 (a) A – Mitochondrion;; 1 Presence of cristae;; 2 Double membrane ;; Reject rod-shaped, reference to cisternae B – Rough endoplasmic reticulum;; 1 Presence of ribosomes;; 2 Parallel stacks of cisternae;; Reject references to sac-like or tube-like structures as not visible on the diagram Examiner’s comments: The features of mitochondria were well known, although some talked about rod-shapes or confused cristae with cisternae. Candidates must ensure that when asked for ‘visible features’ that they only sta te features that they can see on the electron micrograph. Some listed sacs or tubes as features of the rough endoplasmic reticulum. These were not clearly visible on the diagram and reflect what the candidate had learnt rather than what they could see. (b) (i) A – Synthesis of ATP during aerobic respiration;; B – Protein synthesis (by the ribosomes attached to it) / transport of protein / vesicle formation;; (ii) 1 ATP synthesized by A is hydrolyzed to release energy for protein synthesis during translation e.g. amino acid activation;; 2 Ribosomes on B synthesizes respiratory enzymes/proteins needed for aerobic respiration;; Examiner’s comments: Majority of candidates explained how the products of A were useful in B, rather than vice versa (c) 1 Compartmentalisation so that different conditions are established to maintain optimum conditions for enzyme reactions; ; 2 Increase surface area for metabolic reactions e.g. attachment of more electron carriers and ATP synthase for oxidative phosphorylation;;

2010 UCLES ‘A’ Level H2 Biology Mark Scheme 3 QUESTION 2 (a) 1 DNA polymerase works only in one direction, from 5’ to 3’, adding new nucleotides to the available 3’-OH end of a pre-existing polynucleotide chain;; 2 DNA strands are antiparallel /DNA strands run in the 5’ 3’ and 3’ 5’ directions ;; (b) 1 The parental DNA molecule is a double helix consisting of two strands, each strand serves as a template for the synthesis of a new complementary daughter strand;; 2 each of the two new DNA molecules contains one new and one original/parental strand of DNA;; Examiner’s comments: Care must be taken when using the terms like ‘strand’ when describing a DNA molecule. Weaker candidates referred to the newly synthesized DNA molecule as being ‘a strand’. (c) 1 Helicase;; 2 (DNA) Primase;; 3 RNA primer ;; OVP 4 ATP;; 5 Single-stranded binding proteins;; 6 Deoxyribonucleotides;; 7 DNA ligase;; Examin