A2%20Respiration%20test

1
A2 Respiration test

• Total marks 40

2
The diagram below shows some of the stages in
glycolysis
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
cytoplasm

• 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 Krebs
  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

oxidised
ATP
acetyl CoA
matrix
mitochondria
dehydrogenases
NAD/FAD
oxidised
electrons
ATP
oxygen
water
4
Below is a diagram of a mitochondrion

1. Add labels where indicated. 5

matrix
cristae
b) any point on the inner membrane
inner membrane
outer membrane
intermembrane space

1. Indicate on the diagram the precise site of the
   electron transport chain 1

5

• 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

6

• 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 Krebs cycle ETC oxidative
phosphorylation
to reoxidise the last substance/last cytochrome
in the ETC
8

• 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

9

• (ii) D ................................
  ..................................................
  ............................
• 
  ..
• 2

• no reaction occurs
• due to lack of reduced NAD/FAD
• which means lack of hydrogen ions/electrons for
  ETC

10

• 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