|
Objective 3:
AMP v. ADP v. ATP
Objective 4:
Enzymes
Induced Fit (Carboxypeptidase)
Objective 5:
The Active Site of Carboxypetidase
(for more see below)
Objective 10:
Chemiosmosis Video
Chemiosmosis handout
Objective 12:
Chemiosmosis Video
F1 complex (12c)
Objective 13:
Why do our muscles hurt after exercise? (optional)
Objective 14:
ATP challenge: 6-carbon fatty acid
vs. glucose
Objective 16:
Endothermic v. ectothermic
Hot-weather
Hibernators (optional)
Objective 17:
Temperature, size, and metabolic
rate
For
All Creatures Great and Small, One Model Predicts Metabolic Rate
(optional)
Optional Supplementary Material:
More on carboxypeptidase 1,
2
Where do all those ATP come from?
Energy changes in endergonic reactions
Enzymes promote catalysis
by different mechanisms
NADH AND FADH are generated
during the oxidation of glucose
Why are 2.5 ATP produced from
each NADH...?
|
Where do all those ATP come from?
For years the complete oxidation of glucose to CO2 and H2O was thought to
produce a total of 36 ATP, but now the number has been reduced to 30. Why is
this so? The number of ATP produced in glycolysis and the Krebs Cycle by substrate
level phosphorylation is unequivocally known because it is determined by the
stoichiometries of chemical reactions. In contrast, the ATP yield of chemiosmotic
synthesis is less certain because the mechanics of proton pumping, metabolite
transport processes, and ATP synthesis do not require whole numbers or even
have fixed values.
The synthesis of an ATP is driven by the flow of about 3 H+ through ATP synthetase,
but an additional H+ is consumed in transporting ATP from the matrix back
into the cytosol. Hence, about 2.5 ATP are generated as a result of the
flow of
a pair of electrons from NADH to O2. For electrons that enter at carrier
Q, the yield is about 1.5 ATP per electron pair. Hence, as you can see
in the
summary table below, about 30 ATP are formed when glucose is completely
oxidized to CO2; this value supersedes that traditional value of 36 ATP
(and the number
of 32 ATP given in your textbook). You are not responsible for the details
presented in the table, though you should remember that 26 out of the 30
ATP come from chemiosmotic synthesis.
| Reaction Sequence |
ATP yield per glucose |
|
| Glycolysis: Glucose into 2 pyruvic acid (in the cytosol) |
|
| Phosphorylation of glucose |
|
| Phosphorylation of fructose-6-phosphate |
– 1 |
| Synthesis of 2 ATP |
– 1 |
| Synthesis of 2ATP |
+2 |
| 2 NADH are formed |
+2 |
|
| Conversion of pyruvic acid into acetyl CoA (inside mitochondria) |
|
| 2 NADH are formed |
|
|
| Krebs Cycle (inside mitochondria) |
|
| 2 molecules of ATP are formed by substrate level phosphorylation |
+2 |
| 6 NADH are formed |
|
| 2 FADH2 are formed |
|
|
| Chemiosmotic synthesis of ATP (inside mitochondrion) |
|
| 2 NADH formed in glycolysis; each yields 1.5 ATP |
+3 |
| 2 NADH formed in stage II, the oxidation of pyruvic acid; each yields
2.5 ATP |
+5 |
| 6 NADH formed in the Krebs cycle; each yields 2.5 ATP |
+15 |
2 FADH2 formed in the Krebs cycle; each yields 1.5 ATP |
+3 |
|
Total |
+30 |
|
