Practice Questions: Cellular respiration and Photosyntheis
Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.
1. Which of the following processes most likely does not involve anaerobic conditions?
A. yeast causing bread dough to rise B. bacteria working in an aeration tank at a sewage plant C. bacteria in
the soil help in composting D. alcohol is produced in fermentation E. sewage breaks down in a septic tank
2. During aerobic cellular respiration, which of the following is the most common type of reaction to take place
in the cell?
A. hydrolysis B. condensation C. neutralization D. redox E. dehydration
3. The reactants in cellular respiration, glucose, and oxygen are stable compounds. How do these substances
react?
A. the activation energy is reduced by a higher pressure inside the cell B. the activation energy is reduced by
a higher temperature inside the mitochondrion C. the activation energy is reduced by enzymes D. the
activation energy is reduced by inorganic catalysts E. none of the above
4. The following molecules can be found at various stages during cellular respiration:
I. acetyl-CoA
II. carbon dioxide
III. glucose
IV. glyceraldehyde
V. pyruvate
Which of the following sequences represents the above molecules in order from the largest to the smallest
amount of chemical energy?
A. II, I, V, IV, III B. III, IV, V, I, II C. III, IV, I, V, II D. III, I, V, IV, II E. IV, III, II, I, V
5. Aerobic respiration involves which one of the following?
A. the input of energy into cells without sufficient oxygen B. the release of energy in cells without sufficient
oxygen C. the sequence of events in fermentation D. breathing very rapidly, getting too much oxygen into
the blood E. the release of energy in cells with an adequate supply of oxygen
6. Glycolysis can best be described as which of the following kinds of pathways?
A. catabolic and synthetic B. glycolytic and aerobic C. aerobic and catabolic D. anaerobic and catabolic
E. anaerobic and anabolic
7. What is the function of water in oxidative phosphorylation?
A. accept electrons during Krebs cycle B. hydrolyze carbohydrates C. add hydrogen ions to pyruvate at the
end of glycolysis D. supply hydrogen ions E. supply electrons for the reduction of NADP
8. Where in the electron transport chain does the energy come from for the synthesis of ATP?
A. the combination of hydrogen ions, electrons, and oxygen to form water B. the breakdown of water
C. the cytochromes D. an electrochemical gradient across the inner mitochondrial membrane E. oxygen
9. At the end of the electron transport chain, the final product is which of the following?
A. cytochrome oxidase B. pyruvate C. co-enzyme A D. ATP E. water
10. Oxygen that is consumed during cellular respiration is returned to the environment once it has been combined
with which of the following substances?
A. ATP or inorganic phosphates B. elemental carbon C. nitrates or sulfates D. glucose or nitrogen
E. carbon or hydrogen
11. Glucose is slightly modified at the beginning of glycolysis. Which of the following modifications takes place?
A. addition of an atom of oxygen B. addition of a phosphate group C. removal of an atom of oxygen
D. addition of a hydrogen E. removal of a molecule of water
12. The final product from the electron transport chain that contains most of the electrons is which of the
following?
A. cytochrome oxidase B. oxygen C. chlorophyll D. ATP E. water
13. During aerobic cellular respiration, which of the following molecules activates Krebs cycle?
A. citrate B. pyruvate C. cytochrome oxidase D. acetyl coenzyme A E. carbon dioxide
14. Anaerobic respiration is less efficient than aerobic respiration for which of the following reasons?
A. less ATP is produced in anaerobic respiration B. aerobic respiration allows for rapid oxidation during
strenuous exercise C. blood carries more than enough oxygen to support aerobic respiration D. only
bacteria and yeast use anaerobic respiration E. most animals have to breathe air in order to survive
15. The major advantage of aerobic respiration to humans is that we
A. cannot obtain more usable energy from food by aerobic respiration B. must always use anaerobic
respiration for movement C. obtain more usable energy by aerobic respiration D. must always use aerobic
respiration for movement E. cannot release energy from food by anaerobic respiration
16. At the end of glycolysis, most of the energy originally found in glucose is located in molecules of
A. phosphoglyceraldehyde (PGAL) B. reduced NAD C. pyruvate D. ATP E. lactate
17. When glucose undergoes combustion in the presence of air, it releases heat rapidly. In cellular respiration
A. all of the energy is converted to ATP B. enzymes make the reaction take place in small steps C. water
prevents uncontrolled combustion D. no oxygen is needed E. no heat is released
18. When muscles cells do work under anaerobic conditions, the muscle cells
A. use lactate to synthesize glycogen for glycolysis B. use the pyruvate-acetyl-CoA shunt as an alternative
energy source C. get their energy from oxidative phosphorylation instead D. produce lactate and release
energy that way E. stop functioning, which results in cramping
19. From the following list, which is the best definition of anaerobic respiration?
A. respiration by a particular species of yeast B. cellular metabolism with adequate oxygen C. cellular
metabolism in the absence of oxygen D. metabolism in the presence of ample oxygen E. a form of
respiration making use of cytochromes
20. Anaerobic and aerobic respiration are similar in all but one of the following ways. Which one is the
exception?
A. NAD+ is reduced B. carbon dioxide is a product C. ADP is combined with inorganic phosphate to form
ATP D. acetaldehyde is converted into ethanol E. both can release energy from glucose
21. Fatty acids can enter Krebs cycle as which of the following?
A. acetyl-Coenzyme A B. pyruvate C. -ketoglutarate D. phosphoglyceraldehyde (PGAL)
E. oxaloacetate
22. Amino acids can enter cellular respiration, but first they have to be
A. deaminated B. hydrolyzed C. phosphorylated D. converted to glucose E. converted into protein
23. Ethanol fermentation at a brewery is most likely limited by
A. the availability of a carbohydrate source B. the availability of ATP C. the build up of carbon dioxide
D. the build up of alcohol E. the availability of reductant
24. Which of the following most accurately describes the location of chloroplasts in the leaves of most plants?
A. the palisade mesophyll tissue only B. the palisade and spongy mesophyll tissue only C. the upper
epidermis and palisade mesophyll tissues only D. the upper epidermis, palisade, and spongy mesophyll
tissues only E. the palisade and spongy mesophyll tissues, and the guard cells of epidermal tissue
25. Grana are formed from
A. stroma B. photosystem C. lamellae D. thylakoids E. reaction centres
26. Which of the following will affect stomatal opening and closing?
I. air temperature
II. amount to water in the soil
III. brightness of ambient light
IV. turgor pressure of the guard cells
V. humidity
A. I, III and V only B. IV and V only C. I, IV and V only D. I, III, IV and V E. I, II, III, IV and V
27. When photosynthetic membranes are stacked in a chloroplast they are called which of the following?
A. stroma B. lamellae C. grana D. cristae E. vesicles
28. When isolated chlorophyll re-emits light as fluorescence, this shows which of the following?
A. When electron transport is disrupted, electron energy is released as light. B. Chlorophyll must work with
molecules like ATP to trap lig. C. Whole chloroplasts are needed in order for photosynthesis to take place.
D. The light emitted is the same wavelength as the light used to illuminate the chlorophyll. E. Isolated
chlorophyll can convert light energy to chemical energy.
29. In terms of the spectrum of white light, which of the following is the most effective for photosynthesis?
A. geen light B. red light C. blue light D. yellow light E. violet light
30. Which of the following elements is found in a molecule of chlorophyll?
A. iron B. magnesium C. sodium D. sulphur E. manganese
31. The fact that 18O is found in the oxygen produced by photosynthesis, but not in the carbohydrate products,
when photosynthesizing organisms are water labelled with 18O leads to which of the following conclusions?
A. the oxygen in the carbohydrate may come from carbon dioxide B. both water and carbon dioxide are
sources of gaseous oxygen C. carbon dioxide is a possible source of oxygen gas D. oxygen from water ends
up in the carbohydrates E. water is the only possible source of oxygen gas
32. Land plants get the CO2 they need for photosynthesis mostly from
A. breakdown of starch B. carbonates in the soil C. the atmosphere D. carbon fixation in the roots
E. water via the roots
33. Water is lost from plants by the process of
A. translation B. transportation C. transpiration D. translocation E. transcription
34. Which one of the following is not a characteristic of the light reactions?
A. electrons are displaced B. carbon fixation happens C. reduction happens D. energy is converted from a
physical to a chemical form E. they take place in the thylakoids of chloroplasts
35. Which of the following statements concerning the Calvin cycle is true?
I. ATP molecules are needed to keep the reactions going
II. the process makes NADPH + H+
III. reduction occurs
IV. oxygen is a product
V. photophosphorylation occurs
VI. carbon fixation occurs
VII. takes place in the thylakoids of chloroplasts
A. IV, V and VII B. I, VI, and VII C. I, III, and VI D. II, IV, and V E. I, II, III and VI
36. Which of the following events of photosynthesis is concerned immediately with light?
A. production of ATP B. fixation of carbon dioxide C. transfer of energy from chlorophyll to carbon
dioxide D. excitation of chlorophyll E. regeneration of chlorophyll
37. A kind of herbicide works by disrupting the structure of the internal membranes of a chloroplast. Which
segment of photosynthesis would be the most affected?
A. activation of the photosystems B. reduction of chlorophyll C. absorption of light D. manufacture of
ATP E. evolution of oxygen
38. Photophosphorylation specifically refers to the
A. synthesis of glucose via carbon fixation B. splitting water as a result of light C. synthesis of ATP by
photolysis D. reduction of NADPH by electron transport E. synthesis of ATP using light
39. The source of energy for photophosphorylation is
A. light and oxidative phosphorylation B. substrate level and oxidative phosphorylation C. oxidative
phosphorylation D. light E. substrate level phosphorylation
40. Electrons released as a result of photolysis
A. combine with H+ ions and oxygen to form water B. are used directly in the fixation of carbon during the
Calvin cycle C. reduce photosystem I chlorophyll molecules D. reduce photosystem II chlorophyll
molecules E. oxidize NADP+
41. Ultimately, the light reactions
A. make G-3-P and carbon dioxide B. split water and carbon dioxide C. form ATP and absorb carbon
dioxide D. form ATP and NADPH + H+ E. breakdown ATP and water
42. Photophosphorylation involves which of the following?
A. chlorophyll B. a proton gradient across the thylakoids C. production of ATP D. photons E. all of the
above
43. Which of the following statements concerning photolysis is correct?
I. it can take place during the fixation of carbon
II. it involves NADP
III. it occurs in the thylakoid of the chloroplast
IV. oxygen gas is produced
V. in involves at least one carbon-containing compound
A. I and III only B. II and IV only C. I, II, and III only D. III and IV only E. none of the above
44. When photosynthesis occurs, the oxygen that is released comes from
A. chlorophyll B. an intermediate of the Calvin cycle C. a carbohydrate D. water E. carbon dioxide
45. In photosynthesis, the function of water is to
A. supply free electrons B. supply oxygen C. activate chlorophyll D. supply hydrogen ions E. buffer pH
46. What does carbon dioxide combine with during photosynthesis?
A. G3P B. ribulose bisphosphate C. ribulose D. NAD+ E. water
47. Ribulose bisphosphate is converted to 3-phosphoglycerate (PGA) with the addition of
A. oxygen B. G3P and carbon dioxide C. carbon dioxide and water D. oxygen and G3P E. oxygen and
glucose
48. During carbon fixation, which of the following is a product?
A. ATP B. 3-phosphoglycerate C. NADPH D. carbon dioxide E. oxygen
49. What is the name of the first enzyme in the C4 pathway?
A. ribulose bisphosphate carboxylase/oxygenase (rubisco) B. phosphoenolpyruvate carboxylase (PEP
carboxylase) C. oxaloacetate carboxylase (OAA carboxylase) D. succinate dehydrogenase E. pyruvate
kinase
50. Photorespiration occurs principally because of
A. elevated carbon dioxide levels in the leaves due to photosynthesis B. elevated oxygen levels in the leaves
due to cellular respiration C. an increase in oxygenase activity relative to carboxylase activity as temperature
increases D. an increase in light intensity E. none of the above
51. C4 refers to
A. Canada, Chile, China and Cambodia, the countries trying to reduce their CO2 emissions B. the number of
carbons is takes to produce one molecule of PGA C. the number of different types of cells needed to run the
Calvin cycle D. the number of carbons in the first product of the Calvin cycle E. the number of carbons
joined together when PEP is carboxylated
52. Spatial separation refers to
A. the Calvin cycle B. the C4 pathway C. the CAM pathway D. cellular respiration E. oxidative
phosphorylation
53. Temporal separation refers to
A. the Calvin cycle B. the C4 pathway C. the CAM pathway D. cellular respiration E. oxidative
phosphorylation
54. There is a cost associated with the C4/CAM pathways. This cost consists of
A. NADPH B. NADH C. cytochrome oxidation D. ATP E. none of the above
55. In green plants, respiration takes place
A. only during the day time B. only during the night time C. all of the time D. only in cells with no
chlorophyll E. only when photosynthesis stops
Completion
Complete each sentence or statement.
56. Energy transfer in a cell occurs largely through phosphorylating events. The two distinctly different energytransfer mechanisms in cells are called (1) ______________________________ and (2)
______________________________. In (1), the ATP is formed directly in an enzyme-catalyzed reaction.
____________________ ATP molecules are formed this way in glycolysis and another
____________________ ATP in the Krebs cycle. In (2), ATP is formed indirectly. This process involves
many ____________________ reactions with ____________________ being the final electron acceptor. It is
a more complex process than (1) and yields more ATP/glucose. The process mentioned in (2) begins when (3)
____________________ removes two hydrogen atoms from a portion of the original glucose molecule. This
will reduce (3) to (4) ____________________. This is catalyzed by a
___________________________________ enzyme. This reactions occurs ____________________ in
glycolysis and ____________________ times in the Krebs cycle. The molecule mentioned in (4) and its
cousin, FADH2 eventually convert their energy into ATP via ___________________________________.
57. The process of glycolysis occurs in the ____________________ and begins with a molecule of
____________________. Glycolysis is a(n) ____________________ process, as it does not require oxygen.
Glycolysis is a ten step process the highlights of which involve ____________________ molecules of ATP
being used to "prime" the beginning portion of the pathway. Fructose 1,6-bisphosphate is split into
____________________ carbon units. Each of these units reacts in the same way and
____________________ NADH are produced in total. ATP production involves a total of
____________________ molecules from substrate level phosphorylation for a net production from glycolysis
of ____________________ ATP.
58. Mitochondria are round or sausage-shaped organelles that are found throughout the cytoplasm of a cell and
specialize the production of ____________________. This process cannot occur in the absence of
____________________. There are three stages of aerobic cellular respiration that take place within
mitochondria: ____________________ oxidation, the ____________________ cycle, and
____________________ phosphorylation. Only ____________________ cells have mitochondria.
____________________ cells only carry out cellular respiration in their cytoplasm. Mitochondria have a
double membrane; the inner one being highly convoluted, the folds of which are called
____________________. The inner membrane has many proteins and enzymes attached to its inner surface.
The inner membrane also creates two compartments within the mitochondrion. The ____________________
is the inner most space and the ______________________________ lies between the two membranes.
59. NAD+ is a limiting factor in glycolysis. In the absence of ____________________ the conversion of (1)
____________________ to NAD+ via the ______________________________ is prevented from happening.
In eukaryotes, the hydrogen atoms of the molecules mentioned in (1) are transferred to certain organic
molecules in one of two methods: (2) ___________________________________ as can occur in yeast and
___________________________________ as can occur in human cells. In the process mentioned in (2), the
hydrogen atoms are passed to ____________________, which is then converted to a molecule of ethanol.
During this a molecule of ____________________ is oxidized to a molecule of ____________________,
which allows glycolysis to continue on.
60. Photosynthesis is carried out by a number of different organisms, including plants, algae, some protists, and
cyanobacteria. These organisms all contain the green-coloured pigment called (1) ____________________.
This molecule absorbs ____________________ energy and begins the process of photosynthesis. The
molecule mentioned in (1) consists of a ____________________ ring and long ____________________ tail.
This ring contains a ____________________ atom at its centre, surrounded by a ring with
____________________ single and double bonds. The tail of the molecule associates with the
____________________ region of the phospholipid bilayer and helps to ____________________ the
molecule in the membrane.
61. Photosynthesis takes place within ____________________ in three stages: (a) ____________________ light
energy, (b) synthesizing ____________________ and ____________________ and (c) the
____________________ cycle. Stages (a) and (b) comprise the ____________________ reactions, while
carbon dioxide is fixed into carbohydrates in stage (c), which can also be referred to as the
______________________________ reactions. Overall, the process of photosynthesis can be expressed as:
carbon dioxide + water + light ____________________ + water + oxygen
62. Light is a form of ____________________ that travels in wave packets called ____________________.
____________________, embedded in the ____________________ membranes, absorb light of particular
____________________ and through the light reactions, transfer their energy to form
____________________ and ____________________. The reactions of ____________________ fixation
depend on the light reactions for a supply of energy and reductant. (1) ____________________ is the only
pigment that can transfer the energy of light to the carbon fixation reactions of photosynthesis.
____________________ and the carotenoids act as ____________________ pigments, transferring their
energy to (1).
63. The ____________________ reactions begin when ____________________ strike a photosynthetic
membrane. Chlorophyll emits ____________________ light when its excited electrons return to their
____________________ state. A ____________________ contains chlorophyll molecules,
____________________ pigments, and proteins embedded in a (1) ____________________ membrane. The
____________________ complex of a photosystem is composed of a number of ____________________
molecules and ____________________ pigments set in a ____________________ matrix and embedded in
the (1) membrane. An ____________________ pigment absorbs a ____________________ and transfers the
energy from pigment to pigment until it reaches a ____________________ molecule in an area called the (2)
____________________ centre. A(n) ____________________ of the (2) centre chlorophyll molecule absorbs
the transferred energy and is raised to a ____________________ energy level. A ____________________
reaction transfers the excited electron to the primary electron acceptor. Chloroplast membranes contain
____________________ types of photosystems. Photosystem ____________________ is called P700
because its (3) ____________________ spectrum peaks at a wavelength of 700 nm. The chlorophyll a
molecule in the reaction centre of photosystem ____________________ is called P680 because its (3)
spectrum peaks at a wavelength of 680 nm.
64. In the dark, or light-independent reactions, ____________________ is fixed in the ____________________
cycle by the enzyme ____________________, which is located in the (1) ____________________ of the
chloroplast. The primary end product of this cycle is ___________________________________, which may
be converted into glucose and polymerized into ____________________ within the (1), or it can be
transported to the cytoplasm and used to produce glucose and ____________________, which is the main
carbohydrate transported from ____________________ cells of the leaf to other cells of the plant.
65. Rubisco is an ____________________ that is capable of performing either a carboxylation reaction at the
beginning of the Calvin cycle or an ____________________ reaction as in the process of
____________________, so named because it occurs in the presence of ____________________. When this
process occurs, instead of the usual 2 PGA molecules being formed in the Calvin cycle, one molecule of PGA
is formed and one molecule of (1) ____________________. This molecule (1) undergoes subsequent
metabolism such that it results in the release of a molecule of ____________________. This process is seen
as wasteful since around ____________________% of all carbon fixed is lost. This problem is made worse as
the temperature of the environment in which the plant is in ____________________.
66. Two ways in which plants have evolved to reduce the amount of photorespiration that can occur are the C4
and CAM pathways of photosynthesis. Both of these make use of the enzyme _________________________,
which fixes carbon dioxide into a four carbon molecule. In the case of C4 plants, these molecules are made
during the day in the _________________________ cells of the plant and then transferred to the
_________________________ cells where it is decarboxylated to release _________________________,
which then enters the Calvin cycle. The C4 mode of photosynthesis represents a
_________________________ separation of the main events of photosynthesis. In CAM photosynthesis
carbon dioxide is fixed during the _________________________ and stored as an organic acid in the
_________________________. During the day, when the stomata are _________________________, the
organic acids are decarboxylated and the Calvin cycle continues. The CAM mode of photosynthesis
represents a _________________________ separation of the main events of photosynthesis.
67. On a light-response curve, the point at which the rate of photosynthetic carbon dioxide uptake exactly equals
the rate of respiratory carbon dioxide evolution is called the ______________________________. The light
intensity at which the carbon fixation reactions reach a maximum overall rate is the
______________________________. The carbon dioxide-limited phase of the light-response curve is a
plateau because the carbon dioxide availability, not ______________________________, limits the overall
rate of photosynthesis. An increase in temperature has virtually no effect on the overall rate of photosynthesis
within the ______________________________, but causes marked increase in rate within the
______________________________ phase. In general, photosynthesis rates are lower at
____________________ oxygen concentrations. Photosynthetic efficiency of a plant is the net amount of
______________________________ uptake per unit of light energy absorbed. Plants that fix carbon dioxide
by the C4 pathway generally exhibit higher ______________________________ rates at higher temperatures
than do C3 plants. In general, photorespiration rates ____________________ with increasing temperatures in
C3 plants, whereas loss of carbon dioxide by photorespiration is virtually ____________________ in C4
plants.
68. In comparing the structure and function of the mitochondrion and chloroplast, the following can be noted. The
mitochondrion has an inner membrane called the ____________________. One of the functions of this inner
membrane is ___________________________________. The hydrogen ion reservoir is located in the
______________________________ and ATP is synthesized in the ____________________. In the
chloroplast, electron transport takes place on membranes of the ____________________, and one of its
functions is ________________________________________. The hydrogen ion reservoir is located in the
____________________ and ATP synthesis occurs in the ____________________. In order to facilitate
reproduction, independent of cell division, both of these organelles have _________________________ and
_________________________.
69. In a general, overall comparison of the reactions that occur during cellular respiration and photosynthesis, it
can be said that the main reactant in respiration is ____________________, while in photosynthesis it is
______________________________ and _________________________. In contrast to this, the main
products of cellular respiration are _________________________ and _________________________, while
in photosynthesis the main product is ____________________ with an interesting waste product
____________________ that is very useful to many creatures on Earth. Cellular respiration is a process that
____________________ energy , while photosynthesis ____________________ energy.
Short Answer
70. Outline the major events that occur in the breakdown of a molecule of glucose to carbon dioxide and water.
71. Briefly explain how ATP is formed by oxidative phosphorylation of NADH.
g
Answer Section
MULTIPLE CHOICE
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
41.
B
D
C
B
E
D
D
D
E
E
B
E
D
A
C
C
B
D
C
D
A
A
D
E
D
E
C
A
C
B
A
C
C
B
C
D
D
E
D
D
D
42.
43.
44.
45.
46.
47.
48.
49.
50.
51.
52.
53.
54.
55.
E
D
D
A
B
C
B
B
C
D
B
C
D
C
COMPLETION
56. substrate level phosphorylation
oxidative phosphorylation
4
2
redox
oxygen
NAD+
NADH
dehydrogenase
once
3
the electron transport chain
57. cytoplasm
glucose
anaerobic
2
two 3
2
4
2
58. ATP
oxygen
pyruvate
Krebs
oxidative
eukaryotic
Prokaryotic
cristae
matrix
intermembrane space
59. oxygen
NADH
60.
61.
62.
63.
electron transport chain
ethanol fermentation
lactate (lactic acid) fermentation
acetaldehyde
NADH
NAD+
chlorophyll
light
porphyrin
hydrocarbon
magnesium
alternating
hydrophobic
anchor/stabilize
chloroplasts
capturing
ATP/NADPH
NADPH/ATP
Calvin
light
dark or light-independent
glucose
energy
photons
Photosystems
thylakoid
wavelengths
ATP/NADPH
NADPH/ATP
carbon
chlorophyll a
chlorophyll b
accessory
light
photons
red
ground
photosystem
accessory
thylakoid
antenna
chlorophyll
accessory
protein
antenna
photon
chlorophyll a
reaction
electron
higher
64.
65.
66.
67.
68.
redox
two
I
absorption
II
carbon dioxide
Calvin
rubisco
stroma
G3P (glyceraldehyde-3-phosphate)
starch
sucrose
mesophyll
enzyme
oxidation
photorespiration
light
glycolate
carbon dioxide
20
increases
PEP carboxylase
mesophyll
bundle sheath
carbon dioxide
spatial
night
vacuole
closed
temporal
light-compensation point
light-saturation point
light intensity
light-limited phase
carbon dioxide-limited
higher
carbon dioxide
photosynthetic
increase
zero/nil
cristae (pl.), crista (s.)
electron transport / H+ ion transport / ATP synthesis
intermembrane space
matrix
thylakoid(s)
electron transport / H+ ion transport / ATP synthesis
thylakoid interior
stroma
DNA / ribosomes
ribosomes / DNA
69. glucose
carbon dioxide/water
water/carbon dioxide
carbon dioxide/water
water/carbon dioxide
glucose
oxygen
releases
stores
SHORT ANSWER
70. - Glucose enters the cell and enters glycolysis, an enzyme catalyzed reaction that occurs in the cytoplasm,
and results in the production of ATP, NADH, and pyruvate.
- The pyruvate is oxidatively decarboxylated into acetyl-CoA with the further production of pyruvate. This
occurs on the inner mitochondrial membrane.
- The acetyl-CoA enters the Krebs cycle in the matrix of the mitochondria and produces NADH, FADH2,
GTP, and CO2.
- The NADH and FADH2 are oxidized and each lose hydrogen and associated electrons.
- The hydrogen (now a proton) helps to form a proton gradient across the inner mitochondrial membrane.
- The electrons enter the electron transport chain and participate in a series of redox reactions that ends with
oxygen combining with the electrons and some hydrogen to form water.
- The proton gradient drives the synthesis of ATP as the protons re-enter the mitochondrial matrix via special
transport molecules.
71. Electrons from NADH are passed to the enzyme NADH dehydrogenase, which is embedded in the inner
mitochondrial membrane. The hydrogen that is released from the NADH is pumped to the inter membrane
space, thus establishing a proton and pH gradient. The electrons move from electron carrier to electron carrier
in the inner mitochondrial membrane in a series of redox reactions and ultimately combine with oxygen and
protons at the cytochrome oxidase complex to form water. As electrons move along this pathway more
protons, from the dissociation of water, are pumped from the matrix to the intermembrane space adding to the
proton and pH gradient. The protons from the intermembrane space return to the matrix via special ATP
synthase molecules embedded in the inner mitochondrial membrane. As they do, they help to catalyze the
formation of ATP from ADP and Pi.