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AQA A-level Biology paper 1 Questions and Answers Latest (2023 / 2024) (Verified Answers)
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AQA A-level Biology paper 1 Questions and Answers Latest (2023 / 2024) (Verified Answers)
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AQA A-level Biology paper 11. large molecules often contain carbon. why?: they can readily form
bonds with other carbon atoms. this forms a 'backbone'. other atoms
can then attach.
2. describe benedicts test for reducing sugars: add equal volumes of the
sugar sample and benedicts reagent.
heat the mixture in a water bath for 5
minutes. brick red precipitate will form.
3. what is a reducing sugar?: a sugar that can reduce (give electrons to)
another chemical.
4. describe the benedicts test for non reducing sugars: with food sample,
add an equal volume of dilute hydrochloric acid in a test tube.
place test tube in water bath for 5
mins. add sodium
hydrogencarbonate solution.
heat resulting solution with an equal volume of benedicts. solution for
5 minutes. turns orange/brown.
5. what does dilute hydrochloric acid do in the benedicts test for non
reducing sugars?: it hydrolyses any disaccharide into monosaccharides,
,thus also forming reducing sugars.
6. describe the structure of starch: chains of alpha
glucose some chains are branched= amylopetcin
some chains are coiled= amylose
7. what purpose does the structure of amylose serve?: makes the
molecule compact so it is stored more easily.
8. what purpose does the structure of amylopectin serve?: more surface
area for enzymes to work on, thus glucose molecules can be released at
a much quicker rate.
9. how is the structure of starch suited to its function?: 1. starch is
insolube so it doesnt affect water potential
2. it is large enough that it doesnt diffuse out of cells
3. compact enough so that a lot of it can be stored in a small space
4. branched= each end can simultaneously be acted on by enzymes, so
glucose is quickly released
10. how is the structure of glycogen suited to its function?: 1. insoluble, so
no effect on water potential of cell
2. insoluble, so doesnt diffuse out of cells
3. compact, a lot of it can be stored in a small space
,4.very highly branched= each end can simultaneously be acted on by
enzymes, so glucose is quickly released
11.why do animals need highly branched glycogen?: because animals
meta- bolic rate is faster than plants and so needs glucose to be
released quicker.
, 12.describe the structure of cellulose: made up of straight chains of beta
glucose the chains are parallel to each other, so H bonds form cross-
linkages
all the H bonds together strengthens the
cellulose forms microfibrils
13. draw alpha and beta glucose:
14.how does the structure of triglycerides relate to their properties?: 1.
triglyc- erides have a high ratio of energy-storing carbon-hydrogen
bonds to carbon atoms, so its a good source of energy.
2. low mass to energy ratio, so theyre good energy storage molecules.
3. large and non-polar, therefore insoluble, therefore don't affec
osmosis.
4. high ratio of hydrogen to oxygen atoms, so can release water
when oxidised, hence provide a source of water
15. what are the roles of lipids?: 1. source of energy
2. waterproofing
3. insulation
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