Biology > EXAM REVIEW > AQA-7401-2-W-MS-Jun 2019 (All)

AQA-7401-2-W-MS-Jun 2019

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Question Marking Guidance Mark Comments 1. (Reference to) hydrolysis of peptide bonds; 2. Endopeptidase act in the middle of protein/polypeptide OR Endopeptidase produces short(er) polypeptides/ increase number of ends; 3. Exopeptidases act at end of protein/polypeptide OR Exopeptidase produces dipeptides/amino acids; 4. Dipeptidase acts on dipeptide/between two amino acids OR Dipeptidase produces (single) amino acids; 4 Accept chain/chain of amino acids/peptide for polypeptide Accept digest/breakdown/ break for ‘act’ 01.1 Mark points 2, 3 and 4 reject answers where substrate or product is incorrect eg ‘Endopeptidase produces dipeptides’ Ignore references to source and location of enzymes 1. No significant difference (in protein absorption); 2. (because ± 2) SDs overlap; 3. (So mean) percentage absorbed not affected by percentage in diet; 4. Amount of protein (in diet) is not a limiting factor OR Something else is limiting factor eg amount of protease; 5. (But) small range of protein in diet OR (Should) Investigate wider range; 3 max Ignore reference to ‘significance’ unless qualified, eg ‘difference’ 01.2 2. Accept error bar for SD 01.3 1. More/remaining/undigested (protein) broken down; 2. (So more) amino acids absorbed; 3. (Because) protein/food passes again through stomach/ileum; 3 1. Accept all (protein) broken down TOTAL 10 Question Marking Guidance Mark Comments 02.1 1. Increases/more oxygen dissociation/unloading OR Deceases haemoglobin’s affinity for O2; 2. (By) decreasing (blood) pH/increasing acidity; 2 1. Accept more readily 1. Accept releases more O2 2. Reject if reference made to active site 1. High(er) affinity for O2 (than haemoglobin) OR 2 1. Accept holds O2 at lower ppO2 Dissociates oxygen less readily OR Associates more readily; 02.2 2. Allows (aerobic) respiration when diving/at 2. Accept acts as an low(er) pO2 OR oxygen store Provides oxygen when haemoglobin unloaded OR Delays anaerobic respiration/lactate production; 02.3 Correct answer for 2 marks 10.8 to 11 (mins) OR 10 minutes and 48 seconds = 2 marks;; Accept for 1 mark, 10.48 minutes OR Reference to 2057.7 to 2058 (10 700 ÷ 5.2, time oxygen would last if its mass was 1 kg) OR Reference to 56 to 56.3 (10700 ÷ 190, oxygen in 1 kg of seal) OR Reference to 988 (5.2 x 190, oxygen used min-1 by the seal) OR Incorrect answer with correct answer shown in working 2 ..................................................................CONTINUED................................................

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