C H A P T E R
3
Summary of Expectations
Briefly explain each of the following points.
• Stages of aerobic cellular respiration include
glycolysis, transition reaction, the Krebs Cycle,
and the electron transport chain. (3.1)
• Glycolysis occurs in the cytoplasm of all cells
and produces two pyruvate molecules and two
ATP molecules. (3.1)
• Substrate-level phosphorylation involves the
transfer of a phosphate group to ADP to form
ATP. (3.1)
• The transition reaction links the processes of
glycolysis and the Krebs cycle. (3.2)
• The Krebs cycle is a cyclical metabolic
pathway that oxidizes acetyl-CoA to carbon
dioxide and water, forming two molecules of
ATP. (3.2)
• The electron transport occurs in the cristae
of the mitochondrion and involves a series of
electron carriers and multienzyme complexes.
(3.2)
• Oxidative phosphorylation requires oxygen in
order to form ATP molecules. (3.2)
• Most ATP molecule production takes place
during the reactions of the electron transport
chain. (3.2)
• Chemiosmosis involves the production of ATP
molecules when a hydrogen ion gradient is
formed across a membrane by an electron
transport chain. (3.2)
• When oxygen is not present, cells use
anaerobic cellular respiration to produce
ATP molecules. (3.2)
• Photosystems are made up of a network of
chlorophyll pigments. (3.3)
• In cyclic photophosphorylation, electrons are
cycled back into the photosystem. (3.3)
• ATP synthesis occurs within the thylakoids.
(3.3)
• The Calvin cycle has three distinct stages —
fixation of CO2 , reduction of CO2 , and
re-formation of the molecule RuBP. (3.3)
R E V I E W
• The Calvin cycle produces one molecule of
PGAL for every three molecules of CO2 that
enter the cycle. (3.3)
• There are three methods of carbon dioxide
fixation in plants — C3 , C4 , and CAM fixation.
(3.3)
Language of Biology
Write a sentence including each of the following
words or terms. Use any six terms in a concept map
to show your understanding of how they are related.
• aerobic cellular
respiration
• aerobic
• glycolysis
• anaerobic
• pyruvate
• fermentation
• transition reaction
• acetyl-CoA
• Krebs cycle
• electron transport chain
• oxidative phosphorylation
• chemiosmosis
• substrate-level
phosphorylation
• PGAL
• PGAP
• PGA
• PEP
• porin
• cardiolipin
• pyruvate dehydrogenase
complex
• ATP synthase complex
• NADH dehydrogenase
complex
• cytochromes
• proton pumps
• anaerobic cellular
respiration
• deamination
• β-oxidation
• photosynthesis
• chloroplast
• thylakoids
• chlorophylls
• photosystem
• antenna pigment
• reaction centre
• photosynthetic unit
• electron acceptor
• electron transport
system
• cyclic
photophosphorylation
• non-cyclic
photophosphorylation
• photolysis
• Calvin cycle
• carbon fixation
• RuBP carboxylase
• photorespiration
• PGAP
UNDE RSTAN DIN G CON CEPTS
1. Why do cells use energy?
2. What are the four steps of aerobic cellular
respiration?
3. Which of the four steps of cellular respiration
acts on glucose?
4. Which of the four steps of cellular respiration
take place in the mitochondrion?
5. Where is pyruvate produced?
6. Glycolysis I involves substrate-level
phosphorylation.
(a) What is substrate-level phosphorylation?
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(b) Which molecules gain phosphate groups
in glycolysis I?
19. Which product of the Krebs cycle has the most
energy? Explain.
7. How is NADH formed during glycolysis?
8. List the key products of the transition reaction.
20. What is the role of oxygen in aerobic
respiration?
21. If oxygen is not available for the electron
transport chain, how is the Krebs cycle
affected?
9. Where in the mitochondrion does the Krebs
Cycle take place?
10. Acetyl Co-A is produced by the transition
reaction. What happens to each part (acetyl
and Co-enzyme A)?
22. Pyruvate moves into a mitochondrion if
the concentration of pyruvate inside the
mitochondrion is lower than the concentration
outside. What conditions will prevent the net
movement of pyruvate into a mitochondrion?
11. What is meant by the term decarboxylation?
12. List the key products of the Krebs cycle.
13. The Krebs cycle uses matter efficiently. How
is this useful to the cell?
23. Compare the net gain of ATP for glycolysis to
the net gain of ATP for fermentation. How is
fermentation more efficient for cells?
14. Is the Krebs cycle an aerobic or anaerobic
process?
15. Which molecules dissolved in the matrix are
essential in the reactions in the Krebs cycle?
24. Muscle cells can switch to lactic acid
fermentation if oxygen levels are very low.
How is this useful to the body?
16. What are the roles of NADH and FADH2 in the
mitochondrion?
25. Where does the light-dependent reaction take
place?
17. What is chemiosmosis? Where does it take
place?
26. What is photolysis and why is it important for
photosynthesis?
18. (a) Where is the high concentration of
hydrogen ions (H+ ) located in the
mitochondrion?
(b) How did the hydrogen ions get there?
27. What is the product of the Calvin cycle?
28. The Calvin cycle is not very efficient. Explain
this statement.
IN QU IRY
29. Mature human red blood cells do not have any
mitochondria, yet they live for weeks. Predict
which respiration processes red blood cells
most likely use. What metabolic products
would you expect to find in red blood cells
that would support your prediction?
30. Which type of molecule can act as a limiting
factor for reactions that take place within the
mitochondrion? Assume you have access to a
specific toxin that can bind with this molecule
and make it inactive. Predict how the toxin
would affect metabolic processes. What key
product (or absence of product) would support
your prediction?
31. Special centrifuges can be used to separate
various components found in mitochondria
and chloroplasts. The components separate in
a centrifuge tube. For each organelle, which
component is likely to be at the bottom of the
centrifuge tube (because it is the heaviest
component)? Assume that the process of
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MHR • Unit 1 Metabolic Processes
separating these components has not disrupted
the enzyme structures involved in the different
metabolic reactions. Identify ways to verify
your answer.
32. During carbon fixation in the Calvin cycle, CO2
combines with RuBP. Oxygen can also combine
with RuBP, and can prevent CO2 from reacting.
If the ambient temperature is increased, will
this increase or reduce glucose production?
Make a data chart to indicate factors important
to consider when investigating this question.
33. Photosynthesis is an endothermic reaction.
Consider that the temperature in the
environment affects this process. Develop
a testable hypothesis that explores how
temperature affects photosynthesis.
34. Which process produces more thermal energy:
photosynthesis or respiration? Design an
experiment to explore this question.
COMMU N ICATIN G
energy
35. Glycolysis is a series of reactions. Some of
these reactions are endothermic and some of
these reactions are exothermic. Endothermic
reactions form products have more energy
than the reactants. Exothermic reactions
form products that have less energy than the
reactants. Show the relative energy of each of
the following molecules on the energy graph
provided: glucose, fructose-diphosphate,
PGAL, PGA, pyruvate.
reaction progress
36. Make a diagram of the cell showing the cell
membrane, nucleus, cytosol and at least one
mitochondrion. Use one colour to show the
path of one molecule of glucose into the cell,
through glycolysis and into the mitochondrion
for respiration. Use a second colour to show
where energy is used to drive cellular
respiration. Use a third colour to show where
energy is released by cellular respiration.
37. Glycolysis describes the process of breaking
glucose into two pyruvate molecules. Use
words and diagrams to describe this process
in terms of stored energy, free energy and
thermal energy.
38. Acetyl Co-A is a crucial component of cellular
respiration. Use diagrams and captions to
explain how the cell uses acetyl Co-A
efficiently.
39. Make a diagram to show the movement of
hydrogen ions (H+ ) into the intermembrane
space of a mitochondrion. Also show how the
energy from the hydrogen ions is used to make
ATP. Indicate the movement of electrons along
the electron transport chain of a crista. Show
how water is made as a final product of aerobic
cellular respiration.
40. Make a diagram of a mitochondrion and a
chloroplast. Indicate which reactions take
place on membranes and which reactions take
place dissolved in solution. Indicate how the
following molecules move between the two
organelles: glucose, CO2 , O2 , H2O.
41. Make a rough diagram of a cell. Label locations
of cell processes that use ATP. Label locations
where glycolysis produces ATP. Label locations
where aerobic cellular respiration produces
ATP. Explain how a cell can increase the
efficient transfer of ATP within the cell.
42. Use diagrams to show how non-cyclic
photophosphorylation is different from cyclic
photophosphorylation. Explain how one
system uses matter and energy more efficiently.
M A KIN G CON N ECTION S
43. Cells require energy in the form of ATP
molecules. As you have learned, cellular
respiration describes a metabolic pathway
for the carbohydrate glucose. How does
decreasing carbohydrate (glucose) intake
affect cellular energy?
44. In a multicellular organism, different organ
systems, tissues, and specialized cells contribute
to maintaining the health of the body.
(a) List three molecules that must enter cells to
support cellular metabolism.
(b) List three molecules that must be produced
inside cells to support cellular metabolism.
(c) Add the following to the list you made for
part (b), and give reasons for their
inclusion: PGAL, fructose-phosphate,
oxaloacetate, and coenzyme A.
(d) Which substance given in (c) would you
consider adding to your breakfast? Explain.
45. Pyruvate is available as a dietary supplement.
Explain the possible results of adding pyruvate
to your diet.
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