Citric Acid Cycle
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Acetyl CoA is now ready to feed its acetyl group into the
citric acid cycle for further oxidation. The cycle generates
one ATP per turn by substrate-level phosphorylation. Most
of the chemical energy is transferred to NAD+ and a related
electron carrier, the coenzyme FAD, during the redox
reactions. The reduced coenzymes, NADH and FADH2,
transfer high-energy electrons to the electron transport
chain.
Cell respiration occurs in 4 stages: electron transport chain
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, The fourth stage of respiration, the electron transport chain accepts
electrons from the NADH and FADH2 generated in the 1st three steps. In
eukaryotic cells, the inner membrane of the mitochondrion is the site of
electron transport and chemiosmosis, the processes that together
constitute oxidative phosphorylation. In prokaryotes, these processes take
place in the plasma membrane.
Net yield of Glycolysis
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The net yield form glycolysis is 2 ATP and 2 NADH per glucose
No CO2 is produced during glycolysis
The "fall" of electrons during respiration is stepwise, via NAD+ and an electron
transport chain
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Cellular respiration does not oxidize glucose in a single
step that transfers all the hydrogen in the fuel to oxygen at
one time. Rather, glucose and other fuels are broken down
in a series of steps, each catalyzed by a specific enzyme. At
key steps, electrons are stripped from the glucose.
As an electron acceptor, NAD+ functions as an oxidizing
agent during respiration.
Lactic acid fermentation
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During lactic acid fermentation, pyruvate is reduced directly
by NADH to form lactate (the ionized form of lactic acid)
without the release of CO2.
-Lactic acid fermentation by some fungi and bacteria is
used to make cheese and yogurt.
Human muscle cells switch from aerobic respiration to
lactic acid fermentation to generate ATP when O2 is scarce.
This may occur in the early stages of strenuous exercise.
-The waste product, lactate, was previously thought to
cause muscle fatigue and pain, but recent research
suggests instead that increased levels of potassium ions
(K+) may be to blame; lactate appears to enhance muscle
performance.
An overview of cellular respiration
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Cells harvest the chemical energy stored in organic molecules and use it to
regenerate ATP, the molecule that drives most cellular work.
Respiration has four key pathways: glycolysis, pyruvate oxidation, the citric
acid cycle, and oxidative phosphorylation.
The overall catabolic process is:
organic compounds + O2 --> CO2 + H2O + energy (ATP + heat).
Carbohydrates, fats, and proteins can all be used as the fuel, but it is most
useful to consider glucose:
C6H12O6 + 6O2 --> 6CO2 + 6H2O + energy (A TP + heat)
The catabolism of glucose is exergonic, with ΔG = −686 kcal per mole of
glucose.
Give this one a try later!
Acetyl CoA is now ready to feed its acetyl group into the
citric acid cycle for further oxidation. The cycle generates
one ATP per turn by substrate-level phosphorylation. Most
of the chemical energy is transferred to NAD+ and a related
electron carrier, the coenzyme FAD, during the redox
reactions. The reduced coenzymes, NADH and FADH2,
transfer high-energy electrons to the electron transport
chain.
Cell respiration occurs in 4 stages: electron transport chain
Give this one a try later!
, The fourth stage of respiration, the electron transport chain accepts
electrons from the NADH and FADH2 generated in the 1st three steps. In
eukaryotic cells, the inner membrane of the mitochondrion is the site of
electron transport and chemiosmosis, the processes that together
constitute oxidative phosphorylation. In prokaryotes, these processes take
place in the plasma membrane.
Net yield of Glycolysis
Give this one a try later!
The net yield form glycolysis is 2 ATP and 2 NADH per glucose
No CO2 is produced during glycolysis
The "fall" of electrons during respiration is stepwise, via NAD+ and an electron
transport chain
Give this one a try later!
Cellular respiration does not oxidize glucose in a single
step that transfers all the hydrogen in the fuel to oxygen at
one time. Rather, glucose and other fuels are broken down
in a series of steps, each catalyzed by a specific enzyme. At
key steps, electrons are stripped from the glucose.
As an electron acceptor, NAD+ functions as an oxidizing
agent during respiration.
Lactic acid fermentation
, Give this one a try later!
During lactic acid fermentation, pyruvate is reduced directly
by NADH to form lactate (the ionized form of lactic acid)
without the release of CO2.
-Lactic acid fermentation by some fungi and bacteria is
used to make cheese and yogurt.
Human muscle cells switch from aerobic respiration to
lactic acid fermentation to generate ATP when O2 is scarce.
This may occur in the early stages of strenuous exercise.
-The waste product, lactate, was previously thought to
cause muscle fatigue and pain, but recent research
suggests instead that increased levels of potassium ions
(K+) may be to blame; lactate appears to enhance muscle
performance.
An overview of cellular respiration
Give this one a try later!
Cells harvest the chemical energy stored in organic molecules and use it to
regenerate ATP, the molecule that drives most cellular work.
Respiration has four key pathways: glycolysis, pyruvate oxidation, the citric
acid cycle, and oxidative phosphorylation.
The overall catabolic process is:
organic compounds + O2 --> CO2 + H2O + energy (ATP + heat).
Carbohydrates, fats, and proteins can all be used as the fuel, but it is most
useful to consider glucose:
C6H12O6 + 6O2 --> 6CO2 + 6H2O + energy (A TP + heat)
The catabolism of glucose is exergonic, with ΔG = −686 kcal per mole of
glucose.
