AQA A-level Biology paper | Questions With 100% Correct Answers | Verified

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