L Energy and Respiration I PDF
L Energy and Respiration I PDF
L Energy and Respiration I PDF
[2]
[2]
[2]
[2]
(N01/P3/Q5)
2. Oxidative phosphorylation in mitochondria is fuelled not only by the pyruvate produced from glucose
by glycolysis but also by fatty acids. The fatty acids are then broken down in a series of enzyme
controlled steps, in the matrix of mitochondria, which release 2C fragments after they form acetyl
coenzyme A.
a.
Explain what happens to the 2C fragments after they form acetyl coenzyme A.
[3]
b.
State the two main products of oxidative phosphorylation.
[2]
c.
Describe the role of oxygen in oxidative phosphorylation.
[2]
(N00/P3/Q5)
3. a. Outline the main features of the Krebs Cycle.
b. Describe the role of NAD in aerobic respiration.
c. Explain the small yield of ATP from anaerobic respiration.
[8]
[6]
[6]
(N02/P2/Q7)
[9]
[6]
(J08/P4/Q9)
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b.
c.
d.
7. Fig. 2.1 is an electron micrograph showing the main structural features of a mitochondrion in section.
a.
b.
Describe two ways in which the structure of the mitochondrion is adapted for oxidative
phosphorylation.
[2]
[4]
c.
Explain how the lack of oxygen will affect the respiratory processes in the mitochondria.
References to processes in the cytoplasm are not required.
[3]
(J04/P4/Q2)
Waleed Ahmad Khan
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a.
b.
c.
[3]
[3]
[4]
(J05/P4/Q1)
9. The metabolic pathway in which a hexose sugar, such as glucose, is broken down in respiration by
cells starts with glycolysis. Fig. 1.1 outlines the key stages of glycolysis.
a.
b.
c.
d.
[1]
[1]
[2]
[4]
(J06/P4/Q1)
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10. (a) The respiratory quotient (RQ) is used to show what substrates are being metabolised in
respiration. The RQ of a substrate may be calculated using the formula below:
When the unsaturated fatty acid linoleic acid is respired aerobically the equation is:
CO2 + 16H2O + energy
C18H32O2 + 25O2
(i) Calculate how many molecules of carbon dioxide are produced when one molecule of linoleic acid is
respired aerobically.
[1]
(ii) Calculate the RQ for linoleic acid.
[1]
(b) Hummingbirds feed on nectar from flowers only during daylight hours. Nectar is rich in sugars.
Fig. 1.1 shows a hummingbird.
A study of aerobic respiration in captive hummingbirds was carried out. The hummingbirds were allowed
to feed freely and then made to fast for four hours in constant conditions. During this time their RQ values
were calculated every 40 minutes. Fig. 1.2 shows the results from this study.
[4]
(c) Hummingbirds regulate their body temperature whereas butterflies do not regulate their body
temperature. Explain briefly the effect of an increase in temperature on the rate of respiration of a
butterfly.
[2]
(J09/P4/Q1)
Waleed Ahmad Khan
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11. (a) The initial stages of respiration convert one molecule of glucose into two molecules of a 3C
compound.
State
(i) the name given to these initial stages
[1]
(ii) where these stages occur in cells
[1]
(iii) the total number of ATP molecules formed during these stages.
[1]
(b) Most of the ATP formed in respiration is produced within the mitochondria by oxidative
phosphorylation.
(i) State the location, in the mitochondrion, of oxidative phosphorylation.
(ii) Outline the process of oxidative phosphorylation.
[1]
[5]
(c) In an investigation, mammalian liver cells were homogenised (broken up) and the resulting
homogenate centrifuged. Samples of the complete homogenate and samples containing only nuclei, only
ribosomes, only mitochondria or only the remaining cytosol were incubated with:
1 glucose
2 pyruvate
3 glucose and cyanide
4 pyruvate and cyanide
Cyanide inhibits oxidative phosphorylation.
After incubation the presence or absence of carbon dioxide and lactate in each sample was determined.
The results are summarised in Table 7.1.
(i) With reference to Table 7.1, name the two organelles not involved in respiration.
[1]
(ii) Explain why carbon dioxide is produced when mitochondria are incubated with pyruvate but not when
they are incubated with glucose.
[3]
(iii) Explain why, in the presence of cyanide, lactate is produced but carbon dioxide is not.
[3]
(J10/P41/Q7)
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12. Fig. 7.1 is an outline diagram of the Krebs cycle. A two carbon acetyl group enters the cycle by
combining with a molecule of oxaloacetate. A molecule of citrate is formed which is decarboxylated
and dehydrogenated to regenerate the oxaloacetate. The letters P to V are steps in the cycle.
[2]
(ii) Using the letters in the cycle, state where decarboxylation is taking place.
[1]
(b) Fig. 7.1 shows that fatty acids can be converted into acetyl coenzyme A (acetyl CoA) by a process
known as oxidation. Both this process and the Krebs cycle require NAD. The hydrogen atoms released
reduce the NAD molecules.
(i) State the number of reduced NAD molecules that are formed in the Krebs cycle from one acetyl group
that enters the cycle from acetyl CoA.
[1]
(ii) State where the reduced NAD molecules are re-oxidised and describe what happens to the hydrogen
atoms.
[5]
(c) Describe the role of reduced NAD in respiring yeast cells in the absence of oxygen.
[4]
(d) Describe how the production of lactate in muscle tissue differs from anaerobic respiration in yeast.
[3]
(J10/P42/Q7)
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Two stages of respiration occur in mitochondria. These are the Krebs cycle and oxidative
phosphorylation.
(a) Complete the table below by naming the structures labelled A and B and stating which of the stages
of respiration occur in each.
(b) Describe how the structure of a mitochondrion is adapted to carry out these two processes. [3]
(c) Describe briefly the role of NAD in respiration.
[3]
(d) Describe how photophosphorylation differs from oxidative phosphorylation.
[3]
(N02/P4/Q2)
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14. Fig. 2.1 shows the reduction of NAD that occurs during respiration.
(a) State two specific places in the eukaryotic cell where NAD is reduced.
[2]
(b) Describe the role of NAD in cellular respiration.
[3]
(c) Explain why NAD cannot be regenerated from reduced NAD in mitochondria in the absence of
oxygen.
[3]
(d) Yeast can respire aerobically and anaerobically. When there is insufficient oxygen, yeast cells switch
from aerobic to anaerobic respiration. This results in a significant increase in the rate of glucose uptake
and glycolysis in the yeast cells. Suggest why the rate of glycolysis increases significantly when yeasts
cells switch from aerobic to anaerobic respiration.
[2]
(N03/P4/Q2)
15. Fig. 1.1 shows the Krebs cycle and the reactions preceding it.
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[3]
Aerobic respiration uses oxygen and produces carbon dioxide as a waste substance. Animal cell
metabolism can be analysed using the respiratory quotient, RQ. The RQ is the volume of the carbon
dioxide produced divided by the volume of the oxygen consumed.
(b) State typical RQ values for carbohydrates and lipids.
carbohydrate .....................................
lipid .....................................................
[2]
The Siberian hamster, a small rodent like a mouse, had its RQ measured at different air temperatures.
Fig. 1.1 shows the results of this experiment.
(c) Using the information in Fig. 1.1, describe and explain the relationship between RQ and air
temperature.
[4]
(d) State a circumstance under which the RQ value would rise to over 1.0.
[1]
(N06/P4/Q1)
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(a)
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[1]
[2]
(c) Outline how this apparatus is used to measure the rate of oxygen uptake by a known mass of
germinating seeds.
[4]
(d) Explain how the apparatus could be modified to measure the RQ of the germinating seeds.
[2]
(e) Explain why an increase in temperature from 15 C to 25 C will increase the rate of oxygen uptake in
germinating seeds.
[2]
(J02/P4/Q2)
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[8]
(J07/P4/Q2)
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