Mark Scheme – As Biology – 7401-1 – June 2022.

given, will still mean that the mark is not awarded. Question Marking Guidance Mark Comments 01.1 B: is hydrolysed in the ileum and a product of this hydrolysis is found in micelles; A: is formed by a condensation reaction between two α-glucose molecules; C: is formed by the action of DNA polymerase; B: gives a positive result in an emulsion test; 4 (4 x AO1) Question Marking Guidance Mark Comments 01.2 1. Facilitated diffusion of amino acid (into cell when higher concentration in lumen); 2. Co-transport; 3. Sodium ions actively transported from cell to blood/capillary/tissue fluid; 4. Creating sodium ion concentration/diffusion gradient; 5. Facilitated diffusion of amino acid into blood/capillary; 4 max (4 x AO1) 1. and 5. Accept diffusion via channel/carrier proteins for ‘facilitated diffusion’ 3. Accept ‘pumped’ for transported 3. and 4. Accept Na+ for sodium ion(s) 3. and 4. Max 1 if ions not mentioned Question Marking Guidance Mark Comments 02.1 1. RNA/rRNA; 2. Protein; 2 (2 x AO1) Reject tRNA and mRNA Ignore amino acids Question Marking Guidance Mark Comments 02.2 1. DNA has deoxyribose, mRNA has ribose; 2. DNA has thymine, mRNA has uracil; 3. DNA long, mRNA short; 4. DNA is double stranded, mRNA is single stranded; 5. DNA has hydrogen bonds, mRNA has no hydrogen bonds OR DNA has (complementary) base pairing, mRNA does not; 4 max (4 x AO1) Must be comparisons Ignore splicing/introns 4. Accept ‘double helix’ for ‘double stranded’ and ‘single helix’ for ‘single stranded’ Question Marking Guidance Mark Comments 03.1 Flagellum/flagella; 1 (AO1) Question Marking Guidance Mark Comments 03.2 1. 3D with SEM, but 2D with TEM OR (Only) surface visible with SEM, but internal structures visible with TEM; 2. (Because) electrons deflected/bounce off (using SEM) OR Electrons transmitted/pass through (using TEM); 2 (2 x AO1) 2. Accept Resolution is lower (with SEM) 03.3 Shorter wavelength between electrons OR Longer wavelength in light (rays); 1 (AO1) Accept ‘of electrons’ OR ‘of electron beam’ for ‘between electrons’ Reject Electron microscope has a shorter wavelength Reject Light microscope has a longer wavelength Question Marking Guidance Mark Comments Question Marking Guidance Mark Comments 03.4 Mark in pairs: 1 and 2 OR 3 and 4 1. Measure (length of structure) and divide by magnification; 2. Correct conversion from measured length to μm, either × 10 000 from cm OR × 1000 from mm; 3. Measure (length of structure) and divide by (image) length of scale bar; 4. Multiply by actual length of scale bar; 2 (2 x AO1) 1. Accept correct equation making reference to a measurement Question Marking Guidance Mark Comments 03.5 1. Circular DNA (molecule in cytoplasm); 2. Murein cell wall OR Peptidoglycan cell wall OR Glycoprotein cell wall; 3. Small(er)/70S ribosomes (in cytoplasm); 2 max (2 x AO1) Accept mesosome Question Marking Guidance Mark Comments 03.6 1. Capsid; 2. Reverse transcriptase; 3. RNA genome; 4. Envelope; 2 max (2 x AO1) 1. Accept capsomere 1. Ignore protein coat 3. Accept ‘genetic material’ OR ‘genes’ for ‘genome’ Question Marking Guidance Mark Comments 04.1 1. Enters by diffusion; 2. Down a concentration gradient OR From high to low pO2; 3. More/most across parts of body with gills; 4. Gills provide a larger surface area (for absorption); 5. 8.8 (kPa) over gills; 6. 2.4 (kPa - rest of body surface) / 1.9 (kPa - front end before gills) / 0.5 (kPa - rear end after gills); 4 max (4 x AO3) 1. Reject facilitated diffusion 1 and 2 ‘down a diffusion gradient’ = 2 marks 2. Reject ‘along’ for ‘down’ 2. Accept description of O2 is always higher in the water than the lugworm 4. Accept Gills increase SA:volume ratio 04.2 Correct answer for 3 marks, 9.3 × 10–6 / 0.000 0093;;; MP1 – correct reading from graph (1.5) MP2 – correct rearrangement of equation (CdO2 = 0.000 031 × their pO2) MP3 – their CdO2 × 0.2 OR their CdO2 ÷ 5 3 (3 x AO2) Accept correct rounding of 9.3 x 10–6