BIO生物問題----中六

1. Similarity:
Both of them are polymer made up of glucose (monomer)
Both of them consist of glycosidic bond
Difference:
Starch consist of alpha-glucose while celluose consist of beta-glucose
Starch does not have cross-link in between the molecules but celluose have, giving cellulose a rigid structure
Amylose( one type of starch having alpha-1,4 and 1,6 glycosidic bond) is branched while cellulose fibres are always unbranched and parallel to each others

2. Starch does not have cross link in between, they can pack closely to each others. Therefore, they are a good storage substance in human body because they can save space. (Also, starch is osmotic inactive and insoluble to water, therefore they can be stored in human body without upsetting the osmotic potential insde our body)

Cellouse are rigid and since they are beta-glucose, they can only be digested by cellulase found in herbivores.They left in human bodies undigested, so that they can add bulk to other undigested materials and stimulate peristalsis, so as to prevent constipation.

3. Fat and oil are both lipid, both fat is in solid form while oil is in liquid form.

4 The physical properties of lipid is mostly determined by the fatty acids. The higher the degree of saturation, the less soluble the triglyceride is. Also, saturated fatty acids also have a higher melting point and are always in form of solid (fat) in room temperature.

hope this can help you!