Question Marking Guidance Mark Comments
03.1 1. tRNA brings specific amino acid (to ribosome);
2. Anticodon (on tRNA) binds to codon (on
... [Show More] 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
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
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
Question Marking Guidance Mark Comments
05.3 Correct answer for 1 mark, 36:1; 1
Question Marking Guidance Mark Comments
05.4 1. Less (thylakoid) membrane
OR
Fewer/smaller grana;
2. Smaller surface area (of membrane in chloroplast)/less chlorophyll;
3. (Less chlorophyll so) reduced light absorption;
4. (So) slower rate of photosynthesis;
3 max
4. Accept reduced rate of any named biochemical process in photosynthesis; eg. reduced production of ATP/reduced NADP
Question Marking Guidance Mark Comments
06.1 Correct answer for 2 marks, 1.286;; Accept for 1 mark,
1.28571429 (correct answer not to 3 decimal places)
OR
1.285 (incorrect rounding to 3 decimal places)
OR
Evidence of 0.02142857
OR
Evidence of 19 and 4 and 700
OR
Evidence of 15 and 1800 and 2500 OR
Evidence of 15 and 700
2
Question Marking Guidance Mark Comments
06.2 1. C = prophase and D = metaphase and E = anaphase;
2. (In) prophase, chromosomes condense;
3. (In) prophase OR metaphase, centromeres attach to spindle fibres;
4. (In) metaphase, chromosomes/pairs of chromatids at equator/centre of spindle/cell;
5. (In) anaphase, centromeres divide;
6. (In) anaphase, chromatids (from each pair) pulled to (opposite) poles/ends (of cell);
7. (In) prophase/metaphase/anaphase, spindle fibres shorten; If mark point 1 is not credited = 4 max
Do not carry forward error from 1.
Accept letters for stages as indicated in 1.
5 max 2. Accept chromatin for ‘chromosomes’ and for ‘condense’, shorten and thicken
6. Accept for ‘chromatids’, chromosomes but reject homologous chromosomes
7. Accept for ‘shorten’, contract
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
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
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'
Question Marking Guidance Mark Comments
08.4 1. Population 1 grew longer roots in warm temperatures and population 2 grew longer roots in cool temperatures;
2. Standard deviations do not overlap so difference (in mean) unlikely to be/not due to chance;
3. Population 1 (is better adapted to warm conditions because it) has more saturated fatty acids so more energy available (and more growth);
4. Population 2 (is better adapted to cool conditions because it) has more unsaturated/liquid fatty acids so more lipase activity (and more growth);
2. Accept: 'Standard deviations do not overlap showing difference (in mean likely to be) significant'
4
3. and 4. Accept for ‘fatty acids’, fat
Question Marking Guidance Mark Comments
08.5 Same species
OR
(If mated) can produce fertile offspring
OR
(It is) genus and species name;
1
Question Marking Guidance Mark Comments
09.1 4 rows correct = 2 marks;;
2 or 3 rows correct = 1 mark;
0 or 1 row correct = 0 marks
2
Question Marking Guidance Mark Comments
09.2 Correct answer for 2 marks, 0.8376308/0.84/0.8 (hours);;
Accept for 1 mark, Accept correct rounding to any number of decimal places
Evidence of 4 x 106 and 3 x 109 (written in any format, for correct readings from graph)
OR
Evidence of 9.550746785 (correct number of generations)
OR
Evidence of 1.1938443348 (correct generations/ hour)
2
OR
Evidence of 50.26 (correct generation time in minutes)
Incorrect reading of graph, 3 x 106 and 2 x 109
Accept for 1 mark, calculation carried out correctly
Evidence of 9.380821784 (correct calculation of number of generations)
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
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
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 [Show Less]