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All living things derive and use energy by common mechanisms
Making ATP, NADH and Building Blocks from Glucose
Lecture Outline No. 7
Combustion of Carbon Compounds: "In general, respiration is nothing but slow
combustion of carbon and hydrogen, which is entirely similar to what occurs in a lamp or
lighted candle" Antoine Lavoisier, 1789
A) In nonbiological oxidation of methane, two reactions are involved:
(1)Separation of Carbon and Hydrogen to form 4 H2
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H2 |
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H2 |
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H2 |
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H2 |
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CH4 |
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CH3OH |
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CH2O |
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HCOO- |
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O=C=O + Energy |
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H2O |
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H2O |
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Net Reaction 1: CH4 + 2 H2O ® 4 H2 + CO2 + Energy
(2)The combination of Hydrogen and Oxygen to form water.
Net Reaction 2: 4 H2 + 2 O2 ®
4 H2O + Energy
(1) + (2)
CH4 +
2 O2 ® CO2 + 2 H2O
+ Energy
B) In biological oxidations of the above reactions, NAD is the H2
acceptor and the energy released in the reactions is used to make ATP.
NAD is the H2 acceptor in Reaction 1 and 2:
(1) CH4 + 2 H2O + 4 NAD ® 4
NAD:H2 + CO2 + Energy
(2) 4 NAD:H2 + 2 O2
® 4 H2O + 4 NAD + Energy
ATP is made with the energy from reactions 1 and 2.
(1) CH4 + 2 H2O + 4 NAD + Pi + ADP ®
4 NAD:H2 + CO2 + ATP
(2) 4 NAD:H2 + 2 O2 + Pi + ADP ®
4 H2O + 4 NAD + ATP
C) The ATP and NADH cycles.
| ATP |
NAD:H2 |
| Endergonic Ý
ß Exergonic |
Reduction Ý
ß
Oxidation |
| ADP + Pi |
NAD |
D) Common oxidation of glucose in all five Biological Kingdoms!
(1) Separation of Carbons and Hydrogen using NAD as H2 acceptor
C6H12O6 + 6 H2 O + 12 NAD ® 6 CO2 + 12 NAD:H2 + Energy
(2) Combination of H2 with oxygen.
12 NAD:H2 + 6 O2 ® 12 H2O
+ 12 NAD + Energy
(3) ATP is made by coupling to
reactions (1) and (2).
C6H12O6 + 6 O2 + 38 ADP + 38 Pi ® 6 CO2 + 6 H2 O + 38 ATP
E) The Dual Role of Glucose Metabolism: Making Energy and Building Blocks
(1) The complete process is carried
out in about twenty separate reactions. Glycolysis occurs in the cytoplasm of the
cell; others (enclosed in the box below) occur in the mitochondria (Pyruvate oxidation
and Krebs Cycle). Every reaction is catalyzed by a specific enzyme..
Energy Metabolism
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Making Building Blocks |
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Glucose [C6 + 12 :H2]
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Glucose ®
Ribose |
Glycolysis
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ß
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2 ATP ¬ ß ® 2
NAD:H2 ® 4 ATP |
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Triose ® Glycerol,
Fats |
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ß Phospholipids
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2 Pyruvate [C3 + 5 :H2]
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Pyruvate ® Amino Acids |
2 CO2
¬ ß ®
2 NAD:H2® 6 ATP |
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ß
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2 Acetyl-CoA [C2 + 4 :H2]
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Acetyl-CoA® Fatty
acids |
Krebs cycle
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Cholesterol
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2 ATP ¬ ß ® 6
NAD:H2® 18 ATP |
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ß
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ß ®
2 FAD:H2® 4 ATP
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Krebs Acids® Amino
Acids |
4 CO2
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Heme |
(2) The Krebs cycle:
Oxidation of acetyl-CoA via biosynthetic intermediates.
(C4) Oxaloacetate |
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(C4) Oxaloacetate
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¯
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(C2) Acetyl-CoA®
(C6) Citrate® |
(C5)Glutarate®
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(C4) Succinate®
(C4)Malate |
ß
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ß |
ß
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Fatty acids
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Amino Acids |
Amino Acids |
Triglycerides
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Proteins |
Proteins |
Phospholipids
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Heme |
Cholesterol
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