AQA A-LEVEL BIOLOGY PAPER 1 QUESTIONS |
TESTED AND PROVEN ANSWERS | LATEST UPDATE
2024/2025 100% (GRADE A+)
large molecules often contain carbon. why?
Ans>> they can readily form bonds with other carbon atoms. this forms a 'backbone'. other
atoms can then attach.
describe benedicts test for reducing sugars
Ans>> 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.
what is a reducing sugar?
Ans>> a sugar that can reduce (give electrons to) another chemical.
describe the benedicts test for non reducing sugars
Ans>> with food sample, add an equal volume of dilute hydrochloric acid in a test tube.
1
,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.
what does dilute hydrochloric acid do in the benedicts test for non reducing sugars?
Ans>> it hydrolyses any disaccharide into monosaccharides, thus also forming reducing sugars.
describe the structure of starch
Ans>> chains of alpha glucose
some chains are branched= amylopetcin
some chains are coiled= amylose
what purpose does the structure of amylose serve?
Ans>> makes the molecule compact so it is stored more easily.
2
,what purpose does the structure of amylopectin serve?
Ans>> more surface area for enzymes to work on, thus glucose molecules can be released at a
much quicker rate.
how is the structure of starch suited to its function?
Ans>> 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
how is the structure of glycogen suited to its function?
Ans>> 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
3
, 4. very highly branched= each end can simultaneously be acted on by enzymes, so glucose is
quickly released
why do animals need highly branched glycogen?
Ans>> because animals metabolic rate is faster than plants and so needs glucose to be released
quicker.
describe the structure of cellulose
Ans>> 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
draw alpha and beta glucose
Ans>>
4
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