1. A2 Respiration test
Total marks [40]

2. The diagram below shows some of the stages in glycolysis:
Glucose
Hexose phosphate
Hexose biphosphate
Triose phosphate
Pyruvate X Y Z
Reduced Z
State precisely where this process occurs ………………………………………[1]
Identify substance X ……………………………………………..…………………[1]
Identify substance Y ………………………………………………………………..[1]
Briefly outline the fate of substance ‘reduced Z’ …………………………………
………………………………………………………………………………….. ……
………………………………………………………………………………………..[2]
in the cytoplasm
ATP/phosphate group from ATP
hydrogen
Enters mitochondria; is (re-)oxidised; in the electron transport chain;

3. Carefully read the following account of aerobic respiration and then fill in the blanks:
In the first stages of respiration which occurs in the ……………………………………….. of the cell, glucose is ……………………………….. to pyruvic acid. Glycolysis yields ………………………….
and a reduced coenzyme.
The pyruvic acid then combines with coenzyme A to form …………………………………….. which enters the Kreb’s cycle which occurs in the …………………………………………. of the ………………………………………………..
During these reactions hydrogen atoms are removed from a series of intermediate compounds by enzymes called …………………………………… . The hydrogen atoms are passed to carriers such as ……………………………………… .
In the third stage of aerobic respiration, the carriers are alternately reduced and …………………….
as they gain and lose …………………………. . Energy is released and used to phosphorylate ADP, forming ………………………. . The hydrogen atoms finally combine with……………………….. to form …………………………… [13]
cytoplasm
oxidised
ATP
acetyl CoA
matrix
mitochondria
dehydrogenases
NAD/FAD
oxidised
electrons
ATP
oxygen
water

4. Below is a diagram of a mitochondrion
Add labels where indicated. [5]
matrix
cristae
b) any point on the
inner membrane
inner membrane
outer membrane
intermembrane space
Indicate on the diagram the precise site of the electron transport chain [1]

5. The same amount of ADP was added each time.
An experiment was carried out to measure the rate at which a sample of mitochondria used oxygen under different conditions.
The mitochondria were placed in a well oxygenated liquid with a water potential equal to the water potential of their contents.
At time A, an end-product of glycolysis was added to the liquid. At times B, C and D, ADP was added.
The same amount of ADP was added each time.
The results of this experiment are shown in the graph below:
Time (mins)
Oxygen concentration in the liquid A B D C

6. ………………………………………………………………………………………………………… [2]
a) Explain why the liquid used in the experiment should have the same water potential as the contents of the mitochondria
………………………………………………………………………………………………………………………………………………………………………………………………………
………………………………………………………………………………………………………… [2]
to ensure there is no net movement of water/osmosis
that would cause a dilution/concentration of the matrix contents
or damage to mitochondria/bursting of organelle

7. b) (i) State the name of the substance that was added at A
……………………………………………………………… [1]
(ii) Name the two stages of the respiratory process that take place in the mitochondria
……………………………………………………………
………………………………………………………….
[2]
(iii) State the role of oxygen in these respiratory processes
………………………………………………………………
……………………………………………………..……….
[1]
pyruvate/pyruvic acid
link reaction; Kreb’s cycle; ETC; oxidative phosphorylation
to reoxidise the last substance/last cytochrome in the ETC

8. Oxygen concentration in the liquid
c) Explain the result of adding ADP at the following points on the graph;
B and C
……………………………………………………………………………
………………………………………………………………………..… [3]
oxidative phosphorylation can occur/ADP converted to ATP
which requires oxygen
to react with hydrogen to form water
less occurs at C than B because amount of reduced coenzymes is less/ORA
Time (mins)
Oxygen concentration in the liquid A B D C

9. Oxygen concentration in the liquid
(ii) D
……………………………………………………………………..………
[2]
no reaction occurs
due to lack of reduced NAD/FAD
which means lack of hydrogen ions/electrons for ETC
Time (mins)
Oxygen concentration in the liquid A B D C

10. because glycolysis occurs that requires additional ADP
Yeast cells can respire anaerobically using glucose as a substrate.
(i) State the end products formed from the glucose if oxygen is not available to the yeast cells
………………………………………………………………………………………………
……………………………………………………………………………………………… [2]
(ii) Explain why ADP is required in anaerobic conditions
[3]
ethanol/ethanal
carbon dioxide
to form ATP
because glycolysis occurs
that requires additional ADP
to give a net gain of 2 ATP molecules