1.4 - Starch, Glycogen & Cellulose

Question 1

Where is starch found

Answer 1

Plants - in seeds and storage organs, e.g. tubers

Question 2

How is the structure of starch suited to its function

Answer 2

1. Large - Doesnt diffuse out of cells
2. Insoluble - Doesnt change water potential, therefore it doesnt osmose out of cells
3. Compact - Lots can be stored in a small space
4. When hydrolysed, it forms alpha glucose which is easily transported and used in respiration
5. The branched form has many ends which enzymes can simultaneously act upon - releasing lots of glucose monomers

Question 3

Where is glycogen found

Answer 3

Animals - Found in the liver and muscles

Question 4

How is the structure of glycogen suited to its function

Answer 4

1. Insoluble - doesnt bring water in via osmosis
2. Compact, lots stored in a small space. The mass of carbs stored is small because fat is the main storage molecule in animals
3. More highly branched then starch, therefore more enzymes can act simultaneously and release more glucose. This is important because animals have a higher metabolic rate than plants.

Question 5

Where is cellulose found

Answer 5

Plants - Found in the cell wall to provide rigidity

Question 6

How is the structure of cellulose suited to its function

Answer 6

1. Beta glucose forms long, straight and unbranched chains
2. Cellulose chains run parallel and form cross-linkages via hydrogen bonding, adding to collective strength
3. Cellulose molecules form microfibrils which form fibres, providing more strength

Question 7

Differences between starch, glycogen and glucose.

Answer 7

1. Starch and Cellulose are found in plants, Glycogen is found in animals
2. Starch and cellulose are made of Alpha glucose, glycogen is made of Beta glucose
3. Glycogen is more highly branched than starch because the metabolic rate of animals is higher than plants
4. Cellulose is not branched