polysachharide

Question 1

The structure of cellulose is related to its role in plant cell walls. Explain how.

Answer 1

Long / straight / unbranched chains (of glucose joined by) hydrogen bonds;

Q Ignore reference to alpha glucose

Form (micro)fibrils / (macro)fibrils;

Provide rigidity / strength / support;

Question 2

Cotton is a plant fibre used to make cloth. Explain how cellulose gives cotton its strength.

Answer 2

long) straight / unbranched chains;
(idea of more than 1) chains lie side by side / form (micro)fibrils;
idea of H bonds holding chains together;

Question 3

In mammals, in the early stages of pregnancy, a developing embryo exchanges substances with its mother via cells in the lining of the uterus. At this stage, there is a high concentration of glycogen in cells lining the uterus.

(a) Describe the structure of glycogen.

Answer 3

Polysaccharide of α-glucose;

OR

polymer of α-glucose;

2. (Joined by) glycosidic bonds

OR

Branched structure;

Question 4

learn concs

Question 5

Apple farmers want to harvest their fruit when it is ripe enough for eating but also when it can be stored to sell later.

One method apple farmers use to decide when to harvest their fruit is to determine the starch content. As apples ripen, starch in the apple is converted into soluble sugars that make them taste sweet.

Scientists investigated the best time to harvest apples for storage before being sold.

To determine the starch content, they picked samples of apples. They cut each apple in half and covered the cut surface with iodine solution. They left it for 1 minute and then compared it with the diagram below to give it a starch index score between 1 and 10.

The cut surface of the apple covered with iodine solution is left for 1 minute before being compared to Figure 1.

Explain why each apple must be left for the same length of time.

Answer 5

Allow equal (time for) diffusion of iodine into apple cells;

2. For comparison between apples / between harvest dates;