AQA-7182-2-BIOLOGY MARKSCHEME PAPER 2 JUN 2021

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A-LEVEL BIOLOGYMARK SCHEME Practice Paper 2 1 (a)Prevents oxygen being taken up / entering / being absorbed;1 Accept: any idea of no contact with oxygen. Neutral: for anaerobic respiration / anaer... obic conditions. Neutral: prevents entry of air. Reject: prevents entry of oxygen and another named gas. (b)(i) 0.0155 / 0.016 = 2 marks;; 2 0.0775 / 0.077 / 0.078 / 0.08 = 1 mark / 0.62 = 1 mark (ii)Glucose decreases / is a limiting factor / increase in ethanol / yeast /1 cells die / toxins build up; Accept: glucose is used up. (iii)1. (Stays the) same / level / (relatively) constant; 2 2.Same volume / amount of oxygen uptake and carbon dioxide release; Note: if m.p.1 is awarded m.p 2 can be obtained withoutreferring to ‘same volume / amount’. (c)1.Oxygen is final / terminal (electron) acceptor / oxygen combines 2 with electrons and protons; 2.Oxidative phosphorylation / electron transport chain provides (most) ATP/ only glycolysis occurs without oxygen / no Krebs / no link reaction. [Show More]

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