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1. (a) Glycerol / glyceride; 1 (b) (i) Phospholipid has (one) phosphate / Phosphoric acid; replacing fatty acid; 2 (ii) Saturated – all valencies of C filled / saturated with hydrogen / all (C–C) single bonds / no double bonds; fatty acid 1 is saturated/fatty acids 2 and 3 are unsaturated; 2 [5] 2. (a) Several/more than one polypeptide chain in molecule; 1 Evidence must only relate to 4º structure (b) (c) (d) (e) Chemical bonds formed between sulphur-containing groups/ R-groups/form disulphide bonds; Stronger bonds; Bind chain(s) to each other; max 2 Different number of amino acids; Different sequence of amino acids; Bonds in different places; Gives different shape; max 2 Outer layer of skin cells are dead; Do not respire/Do not contain mitochondria; Do not produce ATP/release energy; Cells do not have required proteins/carriers; max 3 1 TEM uses (beam of) electrons; 2 These have short wavelength; 3 Allow high resolution/greater resolution/Allow more detail to be seen/greater useful magnification; 4 Electrons scattered (by molecules in air); 5 Vacuum established; 6 Cannot examine living cells; 7 Lots of preparation/procedures used in preparing specimens / fixing/staining/sectioning; 8 May alter appearance/result in artefacts; max 6 [14] 3. (a) (i) (ii) Initial mass of cylinders not identiical; To be able to directly compare the results; 2 From 0.3 mol dm–3 to 0.1 mol dm–3 water moves into potato cells; By osmosis; So mass increases; More water has entered potato cells 0.1 mol dm–3 / converse; 4 West Bridgford School 1 (iii) (b) 0.35; No mass change/no net osmosis/ volume of water in = volume of water out; Range from –511 to –549 kPa; Reason e.g. Water moves from A to B, so must be lower than –510 and Water moves from B to C, so must be higher than –550; 2 2 [10] 4. (a) (b) A ribosome (RER neutral); 1 B vacuole; 1 C smooth ER / SER; 1 (i) (ii) (c) support / strength / shape / prevents osmotic lysis; (protection, permeability neutral) 1 photosynthesis / light energy → chemical energy; (makes food/sugar neutral) 1 0.2 – 0.24 gains 2 marks; ELSE evidence of observed measurement (5 – 6 mm / 0.5 – 0.6 cm) ÷ 25 000 gains one mark; 2 [7] 5. (i) cold - no / reduced enzyme action / e.g. stops autolysis; (reject “cell activity reduced”) isotonic - stops osmotic effects / description of effect on cells or organelles; buffer - prevents damage to enzymes / proteins; 3 (ii) break open the cells / release the cell contents; 1 (iii) supernatant / liquid above the pellet; spun at a high(er) speed; 2 (mark as independent points) [6] West Bridgford School 2 6. (a) (b) Condensation; removal of water molecule; from amino and carboxyl groups; forming peptide bonds; same amino acids in same sequence; bonds form between R-groups/side chains; e.g. sulphur-containing amino acids / ionic bonds / hydrogen bonds; bonds form in same place; max. 6 Allows passage of charged particles / ions; allows passage of water soluble / large molecules; channel proteins / proteins with pores; specificity related to diameter / charge; carrier proteins; specificity lined to shape of receptor sites; functions by changing shape / conformation; (c) facilitated diffusion with concentration gradient; active transport against concentration gradient; active transport requiring energy / ATP; max. 7 Glucagon has specific shape / structure; receptor molecules with specific receptor sites; concept of fitting; glucagon receptors only on liver cells; max. 4 [17] 7. (a) (i) (ii) (b) potato more negative water potential/hypertonic; (accept more concentrated) water enters by osmosis; cells extend/are turgid; 2 max little/no water remaining in potato/fully plasmolysed/all water has moved out; cell wall prevents further shrinkage/sucrose solution moves in; or, water potentials are equal/equilibrium/isotonic; no net movement of water/no further osmosis; 2 (i) faster rate (of decrease) in 0.8 mol dm–3; 1 (ii) bigger water potential gradient/greater difference in water potentials (between potato and surrounding solution); 1 West Bridgford School 3 (c) (i) (ii) water moved into the solution from the potato; solution diluted/becomes less concentrated; 2 no net movement of water (in or out); drops move up/less dense; or, no net movement of water (in or out); drop would not move/densities the same; 2 [10] West Bridgford School 4