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Chapter 9
Cellular
Respiration
Cellular Respiration
• Used to extract
energy from
organic molecules
Two categories of cellular
respiration
• Aerobic
Cellular
Respiration
• Anaerobic
Cellular
Respiration
Two categories of cellular
respiration
• Aerobic–requires
O2
Large organisms
use aerobic; may
use other
pathways for
short periods
Two categories of cellular
respiration
• Anaerobic–respiration
without oxygen
Used by less active
organisms, and shortterm by others
e.g. Lactic Acid
Fermentation
Aerobic Respiration
• Glycolysis
– first step if glucose is used for
energy
– Occurs in cytoplasm
– Releases 2 ATP
– Glucose is split into 2 molecules
of pyruvic acid
Glycolysis in Aerobic Respiration
• Uses 2 ATP, produces 2 molecules of
the more reactive, higher energy
PGAL
2 ATP
Glucose
PGAL
6C
2 ADP
2
3C
Glycolysis in Aerobic Respiration
• PGAL is now converted to Pyruvate,
releasing energy and electrons
2 NAD(ox)
2 NADH(re)
2 PGAL
3C
4 ADP
2 Pyruvate
3C
4 ATP
Glycolysis in Aerobic Respiration
• Net Results
1 Glucose + 2 NAD + 2 ADP
2 Pyruvate + 2 NADH + 2 ATP
Transition Reaction follows
Glycolysis
• Occurs in the mitochondria
• A preparatory reaction for the Krebs
Cycle
2 NAD(ox)
2 Pyruvate
2 NADH(re)
2 Acetyl CoA + 2 CO2
Citric Acid (Krebs) Cycle
• Occurs in matrix of
mitochondria
• Releases most of the
carbon dioxide
• Makes 6 NADH, 2
FADH2, 2 ATP
• Initial reaction
involves OAA;
regenerates OAA
Citric Acid (Krebs) Cycle
Electron Transport Chain
• Occurs on cristae in
mitochondria
• Uses NADH and
FADH2 to generate
ATP
3 ATP / NADH
2 ATP / FADH2
• Uses oxygen in final
step
Chemiosmosis
during Electron Transport System
• Operation of the system pumps H
ions across cristae into
intermembrane space
• H ion gradient is used as a source of
power
• Enzyme ATP synthase synthesizes
ATP
using the H ion gradient
Chemiosmosis
Chemiosmosis
Summary of Aerobic
Respiration
GLYCOLYSIS
Glucose
2 Pyruvate + 2 ATP + 2 NADH
TRANSITION REACTION
2 Pyruvate
2 Acetyl CoA + 2 CO2 + 2 NADH
KREBS CYCLE
2 Acetyl CoA
4 CO2 + 2 ATP + 6 NADH + 2 FADH2
ELECTRON TRANSPORT SYSTEM
NADH
3 ATP
FADH2
2 ATP
Summary of Aerobic
Respiration
GLYCOLYSIS
Glucose
2 ATP + 2 NADH
TRANSITION REACTION
2 NADH
2 Pyruvate
KREBS CYCLE
2 Acetyl CoA
2 ATP + 6 NADH + 2 FADH2
x3
x2
4 ATP
30 ATP
4 ATP
Total 36 – 38 ATP / Glucose
Anaerobic Respiration
• Lactic Acid
Fermentation
• Alcoholic
Fermentation
• Acetic Acid
Fermentation
Anaerobic Respiration
• Lactic Acid
Fermentation
Glycolysis
then
Pyruvate converted
to Lactic Acid
instead of Acetyl
CoA
Glycolysis in Lactic Acid
Fermentation
• Exactly the same as in Aerobic
Respiration
2 NAD(ox)
Glucose
2 ATP
2 NADH(re)
2 Pyruvate
2 PGAL
2 ADP
4 ADP
4 ATP
Conversion of Pyruvate to Lactic
Acid
2 NADH(re)
2 Pyruvate
2 NAD(ox)
2 Lactic Acid
Net gain of only 2 ATP (from Glycolysis) –
No additional ATP is produced.
Why does the cell bother to produce Lactic Acid?
Lactic Acid Fermentation
2 ADP
Glucose
2 ATP
2 Pyruvate
2 NAD(ox)
2 Lactic Acid
2 NADH(re) 2 NADH(re) 2 NAD(ox)
NAD(ox) is required in glycolysis
Lactic Acid Fermentation
• Why switch to Lactic Acid
Fermentation?
• Why can’t you continue with Lactic
Acid Fermentation for an extended
period of time?
• Why cool down slowly after vigorous
exercise?
Anaerobic Respiration
• Alcoholic Acid
Fermentation
Glycolysis is the first step
then
Pyruvate is converted to Ethyl
Alcohol instead of Acetyl CoA
Glycolysis in Alcoholic
Fermentation
• Exactly the same as in Aerobic
Respiration
2 NAD(ox)
Glucose
2 ATP
2 NADH(re)
2 Pyruvate
2 PGAL
2 ADP
4 ADP
4 ATP
Conversion of Pyruvate to
Ethyl Alcohol
2 NADH(re)
2 Pyruvate
2 NAD(ox)
2 Ethyl Alcohol + 2 CO2
Net gain of only 2 ATP (from Glycolysis) –
No additional ATP is produced.
Why does the cell bother to produce Alcohol?
Alcoholic Fermentation
2 ADP
Glucose
2 ATP
2 Pyruvate
Ethyl
2 Alcohol + 2 CO2
2 NAD(ox) 2 NADH(re) 2 NADH(re) 2 NAD(ox)