T3W2 4E_Pure Biology_Prelim_2023 MS

1 Preliminary Examination 2023 Secondary 4 Express Biology 6093 Mark Scheme Paper 1 1 2 3 4 5 C A B A D 6 7 8 9 10 B A C B D 11 12 13 14 15 C B C B D 16 17 18 19 20 C A C C C 21 22 23 24 25 A A B A B 26 27 28 29 30 B A D A D 31 32 33 34 35 A A C A D 36 37 38 39 40 A A D B D Section A 1 (a)(i) Tissue; reject: incorrect spelling max 1 1 (a)(ii) circular / round shape + label ‘chloroplast’; circular / round shape (larger than drawing of chloroplast) + label ‘nucleus’; large, central oblong shape + label ‘large central vacuole’; line around cell wall (inner) + label ‘cell surface membrane’ reject: incomplete line / broken line/ wrong proportional w.r.t other organelle drawn max 1 1 1 1 4 (a)(iii) Label a pair of guard cell; accept: one guard cell max 1 1 (b) Presence of thin film of moisture; Water evaporates from the thin film of moisture and moves into the intercellular air spaces; AW Presence of intercellular air spaces; 1 1 1

2 Accumulation of water vapour, creating a water vapour concentration gradient between leaf and the surrounding air; max 1 4 2 (a) Similarity: Lactic acid is produced as a by-product/ product ; AW Difference: Carbon dioxide is produced in bacteria but is not produced in muscle cell of human ; AW 1m ea max 1 1 2 (b) From t = 0 to t = 40h, concentration of lactose decreases gradually; AW From t = 40 to t = 48h, concentration of lactose remains unchanged; AW max 1 1 2 (c) Measure 2cm3 of milk and add equal amount of Benedict’s solution; Mix well and heat in a boiling water bath for 5 minutes; max 1 1 2 (d)(i) Mutation / Gene mutation ; There is a change in the allele / gene / base sequence / DNA ; This result in change in the 3- dimensional shape of active site of the enzyme; The substrate / lactose is unable to fit into the active site max 1 1 1 1 3 (d)(ii) Yes; Lactose concentration in yogurt is much low than milk; AW reject: no lactose max 1 1 2 3 (a)(i) Structure A: network of capillaries; Maintains the concentration gradient for the absorption of digested food sustances by the continual transport of digested food substances away; AW Structure B: one cell thick epithelium; Digested food substances take a shorter time to diffuse through, speed up the rate of absorption; max 1 1 1 1 4 (a)(ii) Alveolus / Alveoli; max 1 1 (b)(i) Excess amino acids are transported to the liver for deamination; The amino group will be removed and convert into urea; Urea will be transported to the kidney and excreted from the body in urine; The remaining deaminated amino acids will be convert into glucose. max 1 1 1 3 (b)(ii) Regulation of blood glucose concentration / carbohydrate metabolism; Production of bile / metabolism of fats; Detoxification / Break down alcohol; Break down of red blood cells/ iron storage; Protein synthesis