AQA A-level Biology paper
1||LATEST EXAM
UPDATE||GRADED A+||STUDY
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large molecules often contain carbon. why? -CORRECT 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 -CORRECT 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? -CORRECT ANSWER a sugar that can reduce (give
electrons to) another chemical.
describe the benedicts test for non reducing sugars -CORRECT 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? -
CORRECT ANSWER it hydrolyses any disaccharide into monosaccharides, thus also
forming reducing sugars.
describe the structure of starch -CORRECT ANSWER chains of alpha glucose
some chains are branched= amylopetcin
some chains are coiled= amylose
what purpose does the structure of amylose serve? -CORRECT ANSWER makes the
molecule compact so it is stored more easily.
what purpose does the structure of amylopectin serve? -CORRECT 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? -CORRECT 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? -CORRECT 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? -CORRECT ANSWER because
animals metabolic rate is faster than plants and so needs glucose to be released
quicker.
describe the structure of cellulose -CORRECT 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 -CORRECT ANSWER
how does the structure of triglycerides relate to their properties? -CORRECT 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? -CORRECT ANSWER 1. source of energy
2. waterproofing
3. insulation
4. protection
how does the structure of phospholipids relate to their properties? -CORRECT
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 -CORRECT ANSWER
draw how a dipeptide forms -CORRECT ANSWER
1||LATEST EXAM
UPDATE||GRADED A+||STUDY
NOW||
large molecules often contain carbon. why? -CORRECT 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 -CORRECT 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? -CORRECT ANSWER a sugar that can reduce (give
electrons to) another chemical.
describe the benedicts test for non reducing sugars -CORRECT 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? -
CORRECT ANSWER it hydrolyses any disaccharide into monosaccharides, thus also
forming reducing sugars.
describe the structure of starch -CORRECT ANSWER chains of alpha glucose
some chains are branched= amylopetcin
some chains are coiled= amylose
what purpose does the structure of amylose serve? -CORRECT ANSWER makes the
molecule compact so it is stored more easily.
what purpose does the structure of amylopectin serve? -CORRECT 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? -CORRECT 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? -CORRECT 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? -CORRECT ANSWER because
animals metabolic rate is faster than plants and so needs glucose to be released
quicker.
describe the structure of cellulose -CORRECT 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 -CORRECT ANSWER
how does the structure of triglycerides relate to their properties? -CORRECT 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? -CORRECT ANSWER 1. source of energy
2. waterproofing
3. insulation
4. protection
how does the structure of phospholipids relate to their properties? -CORRECT
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 -CORRECT ANSWER
draw how a dipeptide forms -CORRECT ANSWER
