AQA A-level BIOLOGY (7402/1) Paper 1 Mark scheme 2021 SPECIMEN V1

AQA A-level BIOLOGY Describe how you would use a biochemical test to show that a solution contained a non-reducing sugar, such as sucrose. [3] - ,first reducing sugars test; boil with dilute HCl acid then Neutralise with NaHCǑ, add benedict and heat to 95 degrees C brick red ppt forms if reducing sugar is present Describe a chemical test you could carry out to show that a piece of coconut contains lipids. [3] - (Crush in) ethanol / alcohol; Add (to) water (Order of adding is critical for this point); Emulsion / white colour Explain what is meant by a polymer. [1] - Molecule) made up of many identical/similar molecules/monomers/ subunits; Name the reaction which occurs when starch is broken down into maltose. [1] - Hydrolysis What is the formula for lactose? [2] - C12 ; H22Ō1 Describe how β-glucose molecule differs from a molecule of α-glucose. [1] - H at top right end (instead of OH) / OH at bottom (carbon 1) Show two ways in which the structure of cellulose is different from the structure of starch. [2] - Starch 1,4 and 1,6 bonds / branching Cellulose 1,4 bonds / no 1,6 bonds / straight; starch All glucoses /monomers same way up cellulose Alternate glucoses upside down; starch Helix / coiled/compact cellulose Straight; Starch monomer Alpha glucose Cellulose monomer Beta glucose Describe the structure of starch and explain how its structure is related to its function. [3] - Formed from α glucose; Joined by condensation/ by the removal of a water molecule/ glycosidic bonds; Between (carbons) 1 and 4 (and 1 and 6); Coiled chain; compact; (Allows) storage of large amount in a small space; Insoluble so has no effect on osmosis/water potential; Branches; (Allows) rapid breakdown/release of glucose / hydrolysis; The structure of a phospholipid molecule is different from that of a triglyceride. Describe how. [2] - triglyceride has three fatty acids and phospholipid has two; no phosphate group present in triglyceride but present in phospholipid. What is an unsaturated fatty acid? [1] - Some / two carbons with only one hydrogen / (double bonds) between carbon atoms / not saturated with hydrogen; Describe the structure of cellulose and explain how its structure is related to its function. [3] - Alternate β-glucose rotated 180o, long straight chains, Many hydrogen bonds join