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AQA A-level Biology paper 1 Exam Questions and Answers June 2024
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AQA A-level Biology paper 1 Exam Questions and Answers June 2024
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AQA A-level Biology paper1 Exam Questions and
Answers June 2024
large molecules often contain carbon. why? - Answer>> they
can readily form bonds with other carbon atoms. this forms a
'backbone'. other atoms can then attach.
describe benedicts test for reducing sugars - Answer>> 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? - Answer>> a sugar that can reduce
(give electrons to) another chemical.
describe the benedicts test for non reducing sugars - Answer>>
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.
what does dilute hydrochloric acid do in the benedicts test for non
reducing sugars? - Answer>> it hydrolyses any disaccharide
into monosaccharides, thus also forming reducing sugars.
describe the structure of starch - Answer>> chains of alpha
glucose
,some chains are branched= amylopetcin
some chains are coiled= amylose
what purpose does the structure of amylose serve? - Answer>>
makes the molecule compact so it is stored more easily.
what purpose does the structure of amylopectin serve? -
Answer>> 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? - Answer>>
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? -
Answer>> 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
why do animals need highly branched glycogen? - Answer>>
because animals metabolic rate is faster than plants and so
needs glucose to be released quicker.
describe the structure of cellulose - Answer>> 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 - Answer>>
how does the structure of triglycerides relate to their properties? -
Answer>> 1. triglycerides 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 affect
osmosis.
4. high ratio of hydrogen to oxygen atoms, so can release water
when oxidised, hence provide a source of water
what are the roles of lipids? - Answer>> 1. source of energy
2. waterproofing
3. insulation
4. protection
how does the structure of phospholipids relate to their properties?
- Answer>> 1. polar, therefore will position itself to form a
bilayer
2. the structure allows them to form glycolipids by combining with
carbohydrates within the cell-surface membrane. these are
important in cell recognition.
draw the structure of an amino acid - Answer>>
draw how a dipeptide forms - Answer>>
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