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CHAPTER 9
CELLULAR RESPIRATION
1. _____________________ and ________________ are
catabolic, energy-yielding pathways
Catabolic processes
Complex molecule Enzyme Simpler molecule + heat + energy
(High energy)
(Low energy)
2 common types
1. ________________- to be discussed later
•Organic compounds
CO2 + H2O + Energy
2. ____________________•Organic compounds + O2
Note:
CO2 + H2O + Energy
• This process uses _________.
• This occurs in the _______________
• An example of cellular respiration- _____________ of
glucose
CGlucose
6H12O6 + 6O2
6CO2 + 6H2O + Energy (ATP + heat)
• An ________________reaction
D G = - 686 kcal per mole of glucose.
• Drives the generation of ATP from ADP
ATP then ____________________ other molecules, allowing
them to do work
2. _______ reactions release ___________ when
electrons move closer to _____________ atoms
• _______ (reduction-oxidation) reactions- transfer of
electrons from one reactant to another or changes bond
type (single to double).
• The loss of electrons is called _____________.
• The addition of electrons is called _____________.
• Example:
• NaCl
Na+ + Cl-
• sodium is ____________and chlorine is ____________
• Na is the ____________________ and reduces Cl.
• Cl is the _____________________ and oxidizes Na.
3. Electrons “fall” from organic molecules
to ________ during cellular respiration
• In the summary equation of cellular respiration:
C6H12O6 + 6O2
6CO2 + 6H2O
• Glucose is ___________, oxygen is ____________,
and electrons loose potential energy.
•At key steps, hydrogen atoms are stripped from glucose
and passed first to a coenzyme, like NAD+ (nicotinamide
adenine dinucleotide).
• Dehydrogenase enzymes strip two hydrogen atoms
from the fuel (e.g., glucose), pass _______________
________to NAD+ (to make NADH) and release H+.
• H-C-OH + NAD+ -> C=O + NADH + H+
•NAD + functions as the __________________ in many of the
redox steps during the catabolism of glucose.
Fig. 9.4
•Energy is tapped to
synthesize ATP as
electrons “fall” from
__________ to oxygen.
• The________
___________
_______ breaks
the fall of
electrons to __
into several
steps.
Fig. 9.5
• ________ shuttles electrons to the “top” of the chain.
• At the “bottom”, oxygen captures the ___________ and
___ to form water.
• The free energy change from “top” to “bottom” is ___
kcal/mole of NADH.
Energy used to make ATP!
1. Respiration involves glycolysis, the Krebs
cycle, and electron transport
2. ______________
(in mitochondrial matrix)
1. __________
(In cytoplasm)
3. ___________
____________
(In inner
mitochondrial
membrane)
Fig. 9.6
End result: ATP is generated
2 ADP
Glucose
__________
2 NAD+
__________
__________
2 ATP
6 ADP
2 ADP
2 Pyruvate
_________
_____
2 ATP
______
8 NAD+
2 FAD+
28 ADP
6 CO2
8 NADH
2 FADH2
_________
Add up total ATP generated : 2+2+6+28=___
• In the electron transport chain• the _________ move from molecule to molecule until
they combine with oxygen and hydrogen ions to form
__________.
• As they are passed along the chain, the energy carried
by these electrons is stored in the mitochondrion in a
form that can be used to synthesize ATP via
_____________________________________.
• Oxidative phosphorylation produces almost ____ of
the ATP generated by respiration.
These are generated by ______________________________
2 ADP
Glucose
2 ATP
2 ADP
2 ATP
2 Pyruvate
What is substrate level phosphorylation?
•An _______ transfers a
phosphate group from an
organic molecule (the
substrate) to ____, forming
____.
6 CO2
Enzyme
2. Glycolysis
• Glucose, a six-carbon sugar, is split into two, 3-carbon
sugars then into ________.
• Each of ___ steps in glycolysis is catalyzed by a specific
_________.
Divided into two phases:
1. an _______________
__________
• 2 ATP used
2. an _____________
_________.
• 4 ATP + 2 NADH
produced
Net = 2 ATP + 2 NADH
Glycolysis
Energy investment phase
1st Phosphate group
added
Fig. 9.9a
2nd Phosphate group
added
Two 3-carbon molecules, each with one phosphate
Energy payoff phase
2 PO4
1 PO4
0 PO4
Fig. 9.9b
3. The Krebs cycle completes the energyyielding __________ of organic molecules
2 ADP
Glucose
2 ATP
Glycolysis
2 ADP
2 Pyruvate
Krebs
2 ATP
6 CO2
• If ___________ is present, pyruvate enters the
_________________ where enzymes of the Krebs
cycle complete the ______________ of the organic
fuel to carbon dioxide.
What happens to pyruvate?
• Answer- Pyruvate is modified to ____________
which enters the Krebs cycle in the matrix.
• 1. A _______________ group is removed as CO2.
• 2. A pair of ______________ is transferred from the
remaining two-carbon fragment to NAD+ to form
NADH.
• 3. The oxidized
fragment, acetate,
combines with
coenzyme A to
form ___________
Fig. 9.10
• The Krebs
cycle consists
of ____ steps.
Named after Hans
Kreb – 1930s
• Each cycle
produces
• one ATP by
_____________
_____________
• three ________
• and one ______
Fig. 9.12
• The conversion of
pyruvate and the
Krebs cycle
produces large
quantities of
_______________.
Note the Krebs
cycle is never
depleted of
________: 2 in, 2
out
Fig. 9.11
2 carbon
atoms enter
2 carbon atoms
released as
CO2
4. The inner mitochondrial membrane
couples _____________ to ATP synthesis
• Only __ of __ ATP produced by respiration of
glucose are derived from ________________
________________________.
• The vast majority of the ATP comes from the energy in the
________ carried by ______ (and ________).
• Thousands of copies of the electron transport chain
are found in the _________ (the inner membrane
of the mitochondrion).
• Electrons drop in _____________ as they pass
down the electron transport chain.
• Electrons carried by
__________ are transferred
to the first molecule in the
electron transport chain,
_____________________.
• The electrons continue along
the chain which includes
several ____________
proteins and one lipid
carrier.
• The electrons carried by _____
have lower free energy and are
added to a later point in the chain.
•Electrons from NADH or FADH2
Note: ultimately pass to oxygen.
•The electron transport chain Fig. 9.13
generates no ATP directly.
Then where does the ATP come from??
• A protein complex, ___
_______, in the cristae actually
makes ATP from ADP and Pi.
• ATP uses the energy of
a _____________ (from the
electron transport chain) to
power ATP synthesis.
• This __________________
develops between the
intermembrane space
and the ________.
• Termed _______________
______________________
Fig. 9.14
• This coupling of the redox reactions of the electron transport
chain to ______________ is called _____________________.
Fig. 9.15
•In plants- light supplies the ____________
•In bacteria, the H+ gradient is across the plasma membrane
5. Cellular respiration generates many ___
molecules for each _____ molecule it
_________: a review
• Most energy is from __________________________
glucose NADH
ET chain proton-motive force ATP
• A one six-carbon glucose molecule is oxidized to six CO2
molecules.
• Some ATP is produced by substrate-level phosphorylation
Fig. 9.16
Maximum yield is 38 ATP
• How efficient is respiration in generating ATP?
• Complete oxidation of glucose = _______ kcal/mole.
• Formation of each ATP requires = _____ kcal/mole.
• Efficiency of respiration is
• ____ kcal/mole x ___ ATP/glucose
= ___%.
686 kcal/mole glucose
• The other approximately 60% is lost as ______.
• Cellular respiration is remarkably efficient in
energy conversion.
6. _____________ enables some cells to
produce ATP without the use of _______
• Oxidation refers to the loss of
_______to any electron
acceptor, not just to oxygen.
Fig. 9.17a
• In glycolysis, NAD+ is the
________ agent, not O2.
• Glycolysis generates _____
whether oxygen is present
(aerobic) or not (anaerobic).
Problem- Fermentation (anaerobic catabolism) still
requires NAD+ to accept electrons.
Solution-In _______________, NAD+ comes from the conversion
of pyruvate to _________
• A second solution to the NAD+ problem:
• __________________________
• ( pyruvate is reduced directly by NADH to form
___________)
• Muscle cells switch from _________respiration to lactic
acid ___________ to generate ATP when __ is scarce.
• The waste product,
lactate causes
muscle fatigue but
ultimately it is
converted back to
pyruvate in the liver.
Fig. 9.17b
Compare respiration and fermentation
Similarities
•Both use glycolysis to generate _______
•Both use NAD+ as an _________________.
Type
NAD+
regeneration
Energy
yield
Respiration
Fermentation
Aerobic
Anaerobic
___
___ ATP
Organic molecules
__ ATP
• At a cellular level, human
_________ cells can behave
as facultative anaerobes,
but ________ cells cannot.
• For facultative _________,
pyruvate is a fork in the
metabolic road that leads
to two alternative routes.
Fig. 9.18
7. How do other ________________ fit into
glycolysis and the Kreb cycle??
Answer- ____________
_____________ can all
enter the pathway
•________ are degraded to
amino acids, then
deaminated (nitrogen
secreted as urea, ammonia)
•______________are
broken down to glucose.
•______must be digested to
glycerol and fatty acids.
• Intermediaries in glycolysis and the Krebs cycle
can be diverted to _____________ pathways.
• Examples:
• a human cell can synthesize about ______ the 20
different amino acids by modifying compounds from
the _____________.
• ___________ can be synthesized from pyruvate and
fatty acids from acetyl CoA.
• Excess carbohydrates and proteins can be
converted to _______ through intermediaries of
glycolysis and the Krebs cycle.
8. _____________________ control cellular
respiration
• Basic principles of ____________________ regulate
the metabolic economy.
• If a cell has an excess of a certain amino acid, it typically
uses feedback inhibition to prevent the diversion of more
intermediary molecules from the Krebs cycle to the
synthesis pathway of that amino acid.
• The rate of catabolism is also regulated, typically by
the level of _________ in the cell.
• If ATP levels drop, catabolism speeds up to produce more
ATP.
• Control of catabolism is based
mainly on regulating the activity
of __________ at strategic points
in the catabolic pathway.
• One strategic point occurs in the
third step of glycolysis, catalyzed
by ______________________
•When ATP levels are high,
inhibition of this enzyme slows
________________.
•_____________, the first
product of the Krebs cycle, is
also an inhibitor of
phosphofructokinase.
Fig. 9.20