BIOLOGY paper 2 June
Endopeptidases and exopeptidases are involved in the hydrolysis of proteins. Name the
other type of enzyme required for the complete hydrolysis of proteins to amino acids. -
ANS-dipeptidases
Suggest and explain why the combined actions of endopeptidases and exopeptidases
are more efficient than exopeptidases on their own. - ANS-- endopeptidases hydrolyse
internal peptide bonds
- increase in surface area for exopeptidases
The addition of a respiratory inhibitor stops the absorption of amino acids. Explain why. -
ANS-- no ATP produced
- sodium ions aren't moved into and out of the cell
- no diffusion gradient for sodium to move into cell with amino acid
Suggest appropriate units the student should use to compare the distribution of stomata
on leaves. - ANS-stomata per mm^2
The pieces of leaf tissue examined were very thin. Explain why this was important. -
ANS-- single layer of cells
- so light can pass through
Give two reasons why it was important that the student counted the number of the
stomata in several parts of each piece of leaf tissue. - ANS-- distribution may not be
uniform
- to obtain a reliable mean
Other than the distribution of stomata, suggest and explain two xerophytic features the
leaves of this plant might have. - ANS-- curling of leaves to trap water vapour and water
potential gradient decreased
- thick waxy cuticle increases diffusion distance
Suggest two reasons why the rate of water uptake by a plant might not be the same as
the rate of transpiration. - ANS-- water is used in photosynthesis
Endopeptidases and exopeptidases are involved in the hydrolysis of proteins. Name the
other type of enzyme required for the complete hydrolysis of proteins to amino acids. -
ANS-dipeptidases
Suggest and explain why the combined actions of endopeptidases and exopeptidases
are more efficient than exopeptidases on their own. - ANS-- endopeptidases hydrolyse
internal peptide bonds
- increase in surface area for exopeptidases
The addition of a respiratory inhibitor stops the absorption of amino acids. Explain why. -
ANS-- no ATP produced
- sodium ions aren't moved into and out of the cell
- no diffusion gradient for sodium to move into cell with amino acid
Suggest appropriate units the student should use to compare the distribution of stomata
on leaves. - ANS-stomata per mm^2
The pieces of leaf tissue examined were very thin. Explain why this was important. -
ANS-- single layer of cells
- so light can pass through
Give two reasons why it was important that the student counted the number of the
stomata in several parts of each piece of leaf tissue. - ANS-- distribution may not be
uniform
- to obtain a reliable mean
Other than the distribution of stomata, suggest and explain two xerophytic features the
leaves of this plant might have. - ANS-- curling of leaves to trap water vapour and water
potential gradient decreased
- thick waxy cuticle increases diffusion distance
Suggest two reasons why the rate of water uptake by a plant might not be the same as
the rate of transpiration. - ANS-- water is used in photosynthesis
