Paper 1 recall

textbook answers

How to test for reducing sugars

• add Benedict’s reagent to sample (blue)

• heat in water bath (boiling)

• positive result: coloured ppt forms so reducing sugar present

• increasing conc. of reducing sugar determines colour: green>yellow>orange>brick red

How to test for non-reducing sugars

• heat sample with dilute HCL in water bath (boiling)

• neutralise with sodium hydrogen carbonate

• carry out Benedict’s test

How to test for starch

• add iodine dissolved in potassium iodide solution

• brown-orange to dark blue-black solution

How does the structure of cellulose relate to its function?

long unbranched chains each linked by hydrogen bonds to form microfibrils (strong fibres) - this provides structural support for cells

How does the structure of amylose relate to its function

long unbranched coiled structure (due to angle of glycosidic bonds) - makes it compact so good for storage and fits more glucose in a small space

how does the structure of amylopectin relate to its function

is long with side branches - allows enzyme to hydrolyse glycosidic bonds easily so molecule can be broken down and glucose released quicker

How does the structure of glycogen relate to its function

has long and many side branches - so can be broken down easily and glucose released quicker

compact - so good for storage