AQA A LEVEL BIOLOGY PAPER 2023 QNS MARKING SCHEME, Exams of Nursing

Download AQA A LEVEL BIOLOGY PAPER 2023 QNS MARKING SCHEME and more Exams Nursing in PDF only on Docsity! AQA A LEVEL BIOLOGY PAPER 1 7402-1 2021 MARK SCHEME MS f a ig Z d dW ]W ] _ _h f bm Ẁ ` cZ*Y YdfW ^]%Zi ]faY W[vafwc`wcaWY%V[& A-level BIOLOGY 7402/1 Paper 1 Mark scheme June 2021 Version: 1.0 Final *216a7402/1/MS* MARK SCHEME – A-LEVEL BIOLOGY – 7402/1 – JUNE 2021 3.2 Marking procedure for calculations Full marks can be given for a correct numerical answer, without any working shown. However, if the answer is incorrect, mark(s) can usually be gained by correct substitution / working and this is shown in the ‘Comments’ column or by each stage of a longer calculation. 3.3 Interpretation of ‘it’ Answers using the word ‘it’ should be given credit only if it is clear that the ‘it’ refers to the correct subject. 3.4 Errors carried forward, consequential marking and arithmetic errors Allowances for errors carried forward are most likely to be restricted to calculation questions and should be shown by the abbreviation ECF or consequential in the mark scheme. An arithmetic error should be penalised for one mark only unless otherwise amplified in the mark scheme. Arithmetic errors may arise from a slip in a calculation or from an incorrect transfer of a numerical value from data given in a question. 3.5 Phonetic spelling The phonetic spelling of correct scientific terminology should be credited unless there is a possible confusion with another technical term. 3.6 Brackets (…..) are used to indicate information which is not essential for the mark to be awarded but is included to help the examiner identify the sense of the answer required. 3.7 Ignore / Insufficient / Do not allow Ignore or insufficient is used when the information given is irrelevant to the question or not enough to gain the marking point. Any further correct amplification could gain the marking point. Do not allow means that this is a wrong answer which, even if the correct answer is given, will still mean that the mark is not awarded. 4 MARK SCHEME – A-LEVEL BIOLOGY – 7402/1 – JUNE 2021 Question Marking Guidance Mark Comments 01.1 1. Substrate binds to the active site/enzyme OR Enzyme-substrate complex forms; 2. Active site changes shape (slightly) so it is complementary to substrate OR Active site changes shape (slightly) so distorting/breaking/forming bonds in the substrate; 3. Reduces activation energy; 3 1. Accept for ‘binds’, fits Question Marking Guidance Mark Comments 01.2 Adenosine diphosphate; 1 Question Marking Guidance Mark Comments 01.3 Mark in pairs, 1 and 2 OR 3 and 4 OR 5 and 6 1. Boil OR Add (strong) acid/alkali; 2. Denatures the enzyme/ATP synthase; OR 3. Put in ice/fridge/freezer; 4. Lower kinetic energy so no enzyme-substrate complexes form; OR 5. Add high concentration of inhibitor; 6. Enzyme-substrate complexes do not form; 1. Accept heat at > 50oC OR at very high temperatures 2. Accept for 'denatures', a description of denaturation 2 4. Accept ES for enzyme substrate complex 5 MARK SCHEME – A-LEVEL BIOLOGY – 7402/1 – JUNE 2021 Question Marking Guidance Mark Comments 01.4 1. (With) increasing Pi concentration, more enzyme-substrate complexes are formed; 2. At or above 40 (mmol dm-3) all active sites occupied OR At or above 40 (mmol dm-3) enzyme concentration is a limiting factor; 2 6 MARK SCHEME – A-LEVEL BIOLOGY – 7402/1 – JUNE 2021 Question Marking Guidance Mark Comments 03.1 1. tRNA brings specific amino acid (to ribosome); 2. Anticodon (on tRNA) binds to codon (on mRNA); 3. Amino acids join by condensation reaction (using ATP) OR Amino acids join to form a peptide bond (using ATP); 3 Question Marking Guidance Mark Comments 03.2 1. Hydrogen bonds form instead of ionic bonds; 2. Changes the tertiary structure (of the crystallin); 2 2. Ignore reference to active site Question Marking Guidance Mark Comments 03.3 3 correct = 2 marks;; 2 correct = 1 mark; 0 or 1 correct = 0 marks 2 9 mRNA codon for the non-mutant triplet AGG Mutated mRNA codon GGG Mutated DNA triplet CCC MARK SCHEME – A-LEVEL BIOLOGY – 7402/1 – JUNE 2021 Question Marking Guidance Mark Comments 04.1 1. Only use single lines/do not use sketching (lines)/ensure lines are continuous/connected; 2. Add labels/annotations/title; 3. Add magnification/scale (bar); 4. Draw all parts to same scale/relative size; 5. Do not use shading/hatching; 2 max Question Marking Guidance Mark Comments 04.2 1. Blood vessel X – artery/arteriole and Blood vessel Y – vein/venule; 2. (Difference in) lumen size OR (Difference in) wall thickness; 2 Ignore name of blood vessel, eg. (pulmonary) artery Question Marking Guidance Mark Comments 04.3 1. Carry/wash sharp instruments by holding handle OR Carry/wash sharp instruments by pointing away (from body)/down; 2. Disinfect instruments/surfaces; 3. Disinfect hands OR Wash hands with soap (and water); 4. Put organ/gloves/paper towels in a (separate) bag/bin/tray to dispose; 2 max 1. and 2. Accept for ‘instruments’, a suitable named example, eg. scalpel 2. and 3. Accept for ‘disinfect’, sanitise OR use antiseptic 10 MARK SCHEME – A-LEVEL BIOLOGY – 7402/1 – JUNE 2021 Question Marking Guidance Mark Comments 05.1 1. Break open cells/tissue and filter OR Grind/blend cells/tissue/leaves and filter; 2. In cold, same water potential/concentration, pH controlled solution; 3. Centrifuge/spin and remove nuclei/cell debris; 4. (Centrifuge/spin) at high(er) speed, chloroplasts settle out; 1. Accept homogenise and filter 4 2. Accept for ‘same water potential/ concentration’, isotonic 2. Accept for ‘pH controlled’, buffered Question Marking Guidance Mark Comments 05.2 Mark in pairs, 1 and 2 OR 3 and 4 1. DNA; 2. Is not associated with protein/histones but nuclear DNA is OR Is circular but nuclear DNA is linear OR Is shorter than nuclear DNA; 3. Ribosomes; 4. Are smaller than cytoplasmic ribosomes; 2 4. Accept: 70S ribosomes in chloroplast, but 80S ribosomes in cytoplasm 11 MARK SCHEME – A-LEVEL BIOLOGY – 7402/1 – JUNE 2021 Question Marking Guidance Mark Comments 07.1 1. Cell ingests/engulfs the antibody/ADC OR Cell membrane surrounds the antibody/ADC (to take it inside the cell); 2. Lysosomes fuse with vesicle/phagosome (containing ADC); 3. Lysozymes breakdown/digest the antibody/ADC to release the drug; 1. Accept endocytosis for ingest/engulf 3 3. Accept hydrolytic enzyme for lysozyme Question Marking Guidance Mark Comments 07.2 1. ADC will bind to non-tumour/healthy cells; 2. Cause death/damage of non-tumour/healthy cells OR Cause damage to other organs/systems; 2 1. Reject reference to active site Question Marking Guidance Mark Comments 07.3 Correct answer for 2 marks, 9.2 x 10 5‒ ;; Accept for 1 mark, 0.046 (correct mass injected into 23g mouse) 0.000092 (correct answer but not in standard form) 2 Question Marking Guidance Mark Comments 07.4 Mice died OR Not ethical to continue; 1 14 MARK SCHEME – A-LEVEL BIOLOGY – 7402/1 – JUNE 2021 Question Marking Guidance Mark Comments 07.5 1. Tested on other mammals to check for safety/side effects; 2. Tested on (healthy) humans to check for safety/side effects; 3. See if repeat doses stop the tumours regrowing (in Group J); 4. Investigate different concentrations of ADC to find suitable/safe dosage; 2 max 1. Accept named mammal, eg rat 2. Accept: Tested on (healthy) human tissue/cells to check for no side-effects 15 MARK SCHEME – A-LEVEL BIOLOGY – 7402/1 – JUNE 2021 Question Marking Guidance Mark Comments 08.1 1. One glycerol and three fatty acids; 2. Condensation (reactions) and removal of three molecules of water; 3. Ester bond(s) (formed); 3 Accept all marks in suitably labelled diagram OR in a balanced equation Question Marking Guidance Mark Comments 08.2 Palmitoleic acid is an unsaturated fatty acid represented by diagram K; 1 Question Marking Guidance Mark Comments 08.3 1. To increase accuracy/resolution because differences/lengths are small; 2.To increase accuracy because reduces risk of human error; 3.To increase accuracy because roots are less (likely to be) damaged; 4. To reduce error/uncertainty because differences/lengths are small; 1 max Ignore 'precision' 16 MARK SCHEME – A-LEVEL BIOLOGY – 7402/1 – JUNE 2021 OR Evidence of 1.172602723 (correct calculation of generations/ hour) OR Evidence of 51.16822503 (correct calculation of generation time in minutes) OR Evidence of 0.8528037505 (correct calculation of generation time in hours) Incorrect reading of graph, 106.4 and 109.3 OR 106.3 and 109.2 Accept for 1 mark, calculation carried out correctly Evidence of 9.633591475 (correct calculation of number of generations) OR Evidence of 1.204198934 (correct calculation of generations/ hour) OR Evidence of 49.82565445 (correct calculation of generation time in minutes) OR Evidence of 0.8304275742 (correct calculation of generation time in hours) OR Evidence of 0.83, with no other working 19 MARK SCHEME – A-LEVEL BIOLOGY – 7402/1 – JUNE 2021 Question Marking Guidance Mark Comments 09.3 1. (Model) Q and (Name) Semi-conservative (replication); Explanation 2. (Model) P (is unsupported because) There should be two peaks in generation 1 OR (Only) one peak is shown in generation 1 OR There should be 3:1 (ratio) of peaks in generation 2 OR There should not be an intermediate/15N 14N peak in generation 1/2/3 OR The original/generation 0/15N peak should be in generation 1/2/3; 3. (Model) R (is unsupported because) There should be >2 peaks in generation 2/3 OR There should be one wide/overlapping peak in generation 3; Accept answers 2. and 3. in either order Accept for ‘peak’, density OR distribution 3 3. Accept for ‘>2’, many OR several 20 MARK SCHEME – A-LEVEL BIOLOGY – 7402/1 – JUNE 2021 Question Marking Guidance Mark Comments 10.1 1. Polymer of nucleotides; 2. Each nucleotide formed from deoxyribose, a phosphate (group) and an organic/nitrogenous base; 3. Phosphodiester bonds (between nucleotides); 4. Double helix/2 strands held by hydrogen bonds; 5. (Hydrogen bonds/pairing) between adenine, thymine and cytosine, guanine; 5 1. Accept ‘Polynucleotide’ 1. Accept for ‘phosphate’. phosphoric acid Question Marking Guidance Mark Comments 10.2 1. (Simple) diffusion of small/non-polar molecules down a concentration gradient; 2. Facilitated diffusion down a concentration gradient via protein carrier/channel; 3. Osmosis of water down a water potential gradient; 4. Active transport against a concentration gradient via protein carrier using ATP; 5. Co-transport of 2 different substances using a carrier protein; For any answer accept a correct example 5 If no reference to 'small/ non-polar' for 1. accept this idea from 'large/charged' given in description of 2. 2. Reject if active rather than passive 5. For ‘carrier protein’ accept symport OR co- transport protein 21