AS Biological molecules

Question 1

Give two ways in which the structure of starch is similar to cellulose

Answer 1

Are polymers / polysaccharides / are made of monomers / of
monosaccharides;
2. Contain glucose / carbon, hydrogen and oxygen;
3. Contain glycosidic bonds;
4. Have 1−4 links;
Neutral: references to ‘unbranched’, insoluble, formed by
condensation, flexible and rigid
Are made of the monomer glucose = MP 1 and 2 = 2 marks
5. Hydrogen bonding (within structure).
Ignore reference to H bonds between cellulose molecules

Question 2

Give two ways in which the structure of starch is different to cellulose

Answer 2

1. Contains α / alpha glucose;
Assume ‘it’ refers to starch
Accept: converse arguments only if linked directly to
cellulose
Accept: forms α glycosidic bonds
2. Helical / coiled / compact / branched / not straight;
3. 1,6 bonds / 1,6 branching;
4. Glucoses / monomers same way up;
5. No H-bonds between molecules;
6. No (micro / macro) fibres / fibrils.

Question 3

describe structure of glycogen

Answer 3

alpha 1-4 and 1-6 glycosidic bonds
highly branched
polymer of alpha glucose