AQA A-level Biology paper 1 questions
and answers
large molecules often contain carbon. why? - correct answersthey can readily form bonds with other
carbon atoms. this forms a 'backbone'. other atoms can then attach.
describe benedicts test for reducing sugars - correct answersadd 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 answersa sugar that can reduce (give electrons to) another chemical.
describe the benedicts test for non reducing sugars - correct answerswith 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 answersit
hydrolyses any disaccharide into monosaccharides, thus also forming reducing sugars.
describe the structure of starch - correct answerschains of alpha glucose
some chains are branched= amylopetcin
some chains are coiled= amylose
what purpose does the structure of amylose serve? - correct answersmakes the molecule compact so it
is stored more easily.
what purpose does the structure of amylopectin serve? - correct answersmore surface area for enzymes
to work on, thus glucose molecules can be released at a much quicker rate.
