AQA AS BIOLOGY PAPER 2 QUESTION AND
ANSWERS
Glycogen and cellulose are both carbohydrates.
Describe two differences between the structure of a cellulose molecule and a glycogen molecule. -
ANSWER-1. Cellulose is made up of β-glucose (monomers) and glycogen is made up of α-glucose
(monomers)
2. Cellulose molecule has straight chain and glycogen is branched
3. Cellulose molecule has straight chain and glycogen is coiled
4. glycogen has 1,4- and 1,6- glycosidic bonds and cellulose has only 1,4- glycosidic bonds
QUESTION: Starch is a carbohydrate often stored in plant cells.
Describe and explain two features of starch that make it a good storage molecule. - ANSWER-1. Insoluble
(in water), so doesn't affect water
potential
2. Branched / coiled / (α-)helix, so makes molecule compact
, Or
Branched / coiled / (α-)helix so can fit many (molecules) in small area
3. Polymer of (α-)glucose so provides glucose for respiration
4. Branched / more ends for fast breakdown / enzyme action
5. Large (molecule), so can't cross the cell membrane
QUESTION: The cells of beetroot contain a red pigment. A student investigated the effect of temperature
on the loss of red pigment from beetroot. He put discs cut from beetroot into tubes containing water. He
maintained each tube at a different temperature. After 25 minutes, he measured the percentage of light
passing through the water in each tube
(i)
The student put the same volume of water in each tube.
Explain why it was important that he controlled this experimental variable.
(ii)
Describe a method the student could have used to monitor the temperature of the water in each tube. -
ANSWER-(i)
ANSWERS
Glycogen and cellulose are both carbohydrates.
Describe two differences between the structure of a cellulose molecule and a glycogen molecule. -
ANSWER-1. Cellulose is made up of β-glucose (monomers) and glycogen is made up of α-glucose
(monomers)
2. Cellulose molecule has straight chain and glycogen is branched
3. Cellulose molecule has straight chain and glycogen is coiled
4. glycogen has 1,4- and 1,6- glycosidic bonds and cellulose has only 1,4- glycosidic bonds
QUESTION: Starch is a carbohydrate often stored in plant cells.
Describe and explain two features of starch that make it a good storage molecule. - ANSWER-1. Insoluble
(in water), so doesn't affect water
potential
2. Branched / coiled / (α-)helix, so makes molecule compact
, Or
Branched / coiled / (α-)helix so can fit many (molecules) in small area
3. Polymer of (α-)glucose so provides glucose for respiration
4. Branched / more ends for fast breakdown / enzyme action
5. Large (molecule), so can't cross the cell membrane
QUESTION: The cells of beetroot contain a red pigment. A student investigated the effect of temperature
on the loss of red pigment from beetroot. He put discs cut from beetroot into tubes containing water. He
maintained each tube at a different temperature. After 25 minutes, he measured the percentage of light
passing through the water in each tube
(i)
The student put the same volume of water in each tube.
Explain why it was important that he controlled this experimental variable.
(ii)
Describe a method the student could have used to monitor the temperature of the water in each tube. -
ANSWER-(i)
