large molecules often contain carbon. why? - they can readily form bonds with other carbon
atoms. this forms a 'backbone'. other atoms can then attach.
describe benedicts test for reducing sugars - add equal volumes of the sugar sample and
benedicts reagent.
heat the mixture in a water bath for...
AQA A-level Biology paper 1
large molecules often contain carbon. why? - ✔✔✔they can readily form bonds with other carbon
atoms. this forms a 'backbone'. other atoms can then attach.
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.
what is a reducing sugar? - ✔✔✔a sugar that can reduce (give electrons to) another chemical.
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.
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.
describe the structure of starch - ✔✔✔chains of alpha glucose
some chains are branched= amylopetcin
some chains are coiled= amylose
,what purpose does the structure of amylose serve? - ✔✔✔makes the molecule compact so it is stored
more easily.
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.
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
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
why do animals need highly branched glycogen? - ✔✔✔because animals metabolic rate is faster than
plants and so needs glucose to be released quicker.
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
draw alpha and beta glucose - ✔✔✔
, how does the structure of triglycerides relate to their properties? - ✔✔✔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? - ✔✔✔1. source of energy
2. waterproofing
3. insulation
4. protection
how does the structure of phospholipids relate to their properties? - ✔✔✔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 - ✔✔✔
draw how a dipeptide forms - ✔✔✔
what is meant by 'primary sequence' of a protein - ✔✔✔The unique sequence of amino acids that
make up a protein or polypeptide chain
what is meant by 'secondary sequence' of a protein - ✔✔✔The way in which the primary structure of a
polypeptide chain folds e.g. alpha helix or beta pleated sheets. shape is held by H bonds.
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