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Question 1
(a)
GCE: Biology B – BYB1
January 2002
Biuret reagent / Add NaOH and CuSO4; (ignore heated) Positive result = violet/mauve/lilac/purple coloration; (NOT blue) 2 1 1
(b)
(i) (ii) (iii)
Nitrogen / N; (NOT N2) Condensation; Must have box correct (allow HN / NH, but must have C=O correct)
H H2N C H C O
H N C CH2 SH
O C OH
Total
5
Question 2
(a) (i) (ii) (b) X 6.2; Active transport / active uptake; Ref. to carrier/intrinsic/pore/gate/transport/pump proteins; Ref. to different numbers of carrier proteins; Ref. to specificity / different types of carrier proteins; Ref. to charge / size of ion; For respiration; Energy for active transport; Total 1 1
2 max
(c)
1 max 5
Question 3
(a) (b) (c) (i) A = Epithelium (ignore type of epithelium) / Endothelium; Muscle; X = Mitochondria; Y = Microvilli / brush border; X = Provide energy/for active uptake; Y = Increase surface area; Total 1 1
2
(ii)
2 6
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Question 4
(a) (b) 82%
GCE: Biology B – BYB1
January 2002
1
Concentration gradient maintained over whole lamella; Diffusion gradient maintained / oxygen taken up over whole lamella; Equilibrium never reached; ü ü
2 max
(c) ü 2 (d) Remove one mark for each incorrect tick to minimum mark of zero Decreases surface area; (Thick wall) slows down diffusion rate / increases diffusion pathway; (NOT less diffusion) Mask increases concentration gradient / difference; Total
3 8
Question 5
(a) Faster gas exchange / diffusion; Large / big / increased surface area / shorter pathway for gas exchange / Hb not too far from membrane; (NOT more / bigger / greater / easier / more efficient) OR Increases flexibility; To pass through capillaries; Protein synthesis / Cell division / Mitosis; (NOT Meiosis) (i) Monolayer; Tails up / heads in water; (NOT completely submerged or floating in air) 0.5 / ½; Phospholipids are arranged in a bilayer; Total
2 1
(b) (c)
2
(ii)
2 7
Question 6
(a) Osmosis transports water; Proteins / carrier molecules not used / occurs through phospholipid bilayer; Jam has a lower (more –ve) water potential than the bacterial cytoplasm; Water leaves the bacteria; Effect (of water loss) on bacteria e.g. killed / chemical reactions cannot occur; Total
2
(b)
3 5
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Question 7
(a) (b) Active site;
GCE: Biology B – BYB1
January 2002
1
Substrate enters active site; Complimentary shapes / Lock and Key; (Binding) to form enzyme-substrate complex; Lowering of activation energy; Conformational / shape change; Breaking of bonds in substrate; Products no longer fit active site and so are released; Molecule A binds at site away from active site / allosteric site; Causes enzyme / active site to change shape; Molecule B can enter / competes for active site; Prevents substrate from entering / no enzyme-substrate complex formed / active site blocked; (i) Secretes enzymes (for extra-cellular digestion); Absorbs products; Optimum pH is 7 / neutral / between 6 and 8 / between 7 and 8; Max rate = Distance / Time 11 / 4 11 4 x 60 ;
4
(c)
4
(d)
2 1
(ii) (iii)
2
[Correct answer = 2 marks (IGNORE units) e.g. 2.75 mm / hour, 0.046 mm/min, 4.6 x 10-3 mm/min 1 mm/ 21.8 mins, 23.76mm2/hour] Total 14
Both correct = 1mark ; Correct = second mark; B; Fragment 3 is the second biggest molecule and so will travel second least distance;
Rf = Distance travelled by spot ; 79 mm to 82 mm Distance travelled by front 129 mm 129mm = 0.61 - 0.64
2
2
(c)
2
MUST be 2DP Correct answer = 2 marks (d) (i) A; As there are two molecules composed of 5 aa / the same size / contains fragments 2 and 5; Use 2 way/2D chromatography / Rotate chromatogram 90o; Use a different solvent; Long chains of aa; Folding of chain into a coil / folds / helix / pleated sheet; Association of several polypeptide chains together; Formation of fibres / sheets explained; 2 1
2
(ii)
2
(e)
H bonds / Disulphide bonding (In context); Fibres provide strength (and flexibility); Sheets provide flexibility; Example e.g. keratin in hair, collagen in bone; (MUST be in context) Insoluble because external R-groups are non-polar; Total
