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Chapter 4 Cells and Energy
Cellular Respiration
Cellular respiration
Process by which food molecules are broken down to release energy
Glucose and other 6-carbon sugars are major sources of energy
Aerobic processes require oxygen Anaerobic processes don’t need oxygen
Releasing energy with O2
process involves 4 steps Glycolysis Converting pyruvic acid to acetic acid Citric acid cycle (Kreb’s cycle) Electron transport chain
Glycolysis
6-carbon glucose breaks down to 2 molecules of pyruvic acid (each with 3-carbons)
No oxygen required Also produces 2H+ ions and 2electrons
that are picked up by 2NAD+ Uses 2ATP and produces 4ATP (net
production of 2ATP) Occurs in cytoplasm
GlycolysisGlycolysis
Glucose
2ATP2ADP
2PGAL
4ADP + 4P
2NAD+
2NADH + 2H+
4ATP
2 Pyruvic acid
Fermentation
Lactic Acid Pyruvic acid from glycolysis is converted to
lactic acid NADH + H+ is recycled to NAD+
Alcoholic Pyruvic acid from glycolysis is converted to
ethyl alcohol and carbon dioxide NADH + H+ is recycled to NAD+
Fermentation
Lactic acid fermentation occurs in cytoplasm of muscle cells (causes muscle soreness)
Alcoholic fermentation occurs in bacteria and yeast
Both forms occur in the cytoplasm WITHOUT oxygen
Pyruvic acid to acetic acid
2 Pyruvic acids moves from the cytoplasm into the mitochondria
Each pyruvic acid loses a C to CO2 to make acetic acid
2 Acetic acids are combined with coenzyme A to make 2 acetyl-CoA
2H+ and 2 electrons are picked up by NAD+
Pyruvic acid
Outside the mitochondrion
Mitochondrial membrane
Inside the mitochondrion
Pyruvic acid
Intermediate by-product NAD+
NADH + H+
CO2
Coenzyme A
- CoAAcetyl-CoA
Pyruvic AcidPyruvic Acid
Citric acid cycle (Kreb’s cycle)
Each acetyl-CoA enters the cycle and combines with the 4-carbon oxaloacetic acid to make citric acid
Citric acid loses a C to CO2 and releases H+ to NAD+ to become ketoglutaric acid
Ketoglutaric acid loses a C to CO2, stores energy in an ATP and releases H+ and electrons to NAD+ to make succinic acid
Kreb’s continued
Succinic acid releases H+ and electrons to NAD+ and FAD and converted back to oxaloacetic acid
Products of Kreb’s cycle 4 CO2
2 ATP 6 NADH + H+ 2 FADH
The Citric Acid CycleThe Citric Acid Cycle
(Acetyl-CoA)
Citric acid NAD+
NADH + H+
O= =O(CO2)
NAD+
O= =O
(CO2)ADP +
ATP
FADFADH2
Citric Acid Cycle
NAD+
NADH + H+ Oxaloacetic acid
The mitochondria host the citric acid cycle.
NADH + H+
Electron Transport Chain
All NADH + H+ and FADH produced go to the electron transport chain
Each NADH + H+ produces 3 ATP (30 ATP)
Each FADH produces 2 ATP (4 ATP) Electron transport chain produces a total
of 34 ATP
The electron transport chainThe electron transport chain
EnzymeElectron carrier proteins
e -
NADH
FADH2
NAD+
FAD
Electron pathway
4H+ + O2
+ 4 electrons
H2O
H2O
ADP + ATP
Inner membrane
Center of mitochondrion
Space between inner and outer
membranes
Total ATP production
Net ATP in glycolysis is 2 ATP production in Kreb’s is 2 ATP production in ETC is 34
Total = 38 ATP