Cambridge International A Level Biology Revision Guide

Cambridge International A Level Biology
7 a Explain why the energy value of lipid is more than twice that of carbohydrate. [2]
b Explain what is meant by respiratory quotient (RQ). [2]
c Copy and complete the table to show the respiratory substrates with each of the given RQs.
d
e
Respiratory substrate RQ
1.0
0.7
0.9
[3]
Measurements of oxygen uptake and carbon dioxide production by germinating seeds in a respirometer showed
that 25 cm 3 of oxygen was used and 17.5 cm 3 of carbon dioxide was produced over the same time period.
i Calculate the RQ for these seeds. [2]
ii Identify the respiratory substrate used by the seeds. [1]
Dahlia plants store a compound called inulin, which is a polymer of fructose. The structure of fructose is shown in
the diagram.
CH 2 OH
O
CH 2 OH
C
C
H
H
HO
OH
284
C
C
OH
H
Calculate the RQ when inulin is hydrolysed and then respired aerobically. [2]
[Total: 12]
8 Copy and complete the following passage describing the adaptations of rice for growing with its roots
submerged in water.
The stems and leaves of rice plants have very large ............. in tissue called ............., which allow oxygen to pass
from the air to the ............. . The roots are very shallow, giving them access to the higher concentration of .............
in surface water. When oxygen concentrations fall, the roots can oxidise glucose through ............. ............. .
This produces ............., which is toxic. However, the root cells are tolerant of higher concentrations of this
than are most cells and they also contain high concentrations of the enzyme ............. to break it down. [7]