Question 21M.2.HL.TZ2.3d
| Date | May 2021 | Marks available | [Maximum mark: 2] | Reference code | 21M.2.HL.TZ2.3d |
| Level | HL | Paper | 2 | Time zone | TZ2 |
| Command term | Compare and contrast | Question number | d | Adapted from | N/A |
A broad bean is the seed of a species, Vicia faba, in the Fabaceae, a family of flowering plants. This family contains many species that are used as sources of food.
Broad beans are rich in starch and cellulose. Compare and contrast the structure of starch and cellulose.
[2]
a. both polymers of glucose molecules / polysaccharides
OR
both form 1,4 glycosidic bond ✔
b. starch is formed by alpha glucose while cellulose is formed by beta glucose
OR
in starch C1 hydroxyl groups are found in same plane while in cellulose on different planes
OR
in cellulose, alternatively the beta glucose needs to be placed upside-down in order to have C1 hydroxyl groups on the same plane
OR
two types of starch (amylose and amylopectin) but one type of cellulose ✔
One similarity and one difference.
Comparison to cellulose needed.
Candidates seemed to find it difficult to find similarities and differences in structure between starch and cellulose, and many wrote about their functions, or simply mentioned that both were made of "glucose" without referencing that they are both polymers. There was limited recognition that there are two forms of starch: amylose and amylopectin that differ in their degree of branching.
