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About Glucose Oxidation Respiratory Balance Sheet

Respiratory balance sheet is a mathematical calculation of net ATP produced by cellular respiration during glucose oxidation which includes Glycolysis, Krebs Cycle and Oxidative Phosphorylation under aerobic condition utilizing one glucose molecule.

Features of Glucose Oxidation Respiratory Balance Sheet

Certain assumptions were considered while forming the balance sheet:

1. For an oxidizing Glucose molecule, it must follow the cellular respiration process in a sequence such that glucose must follow every step of glycolysis to form 2 molecules of pyruvate.

Pyruvate must enter Krebs Cycle to produce reducing equivalents.

The reducing equivalents from Glycolysis and Krebs cycle must enter Electron Transport Chain where they get converted into ATP.

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2. Reducing equivalents such as the NADH must carried to Electron Transport Chain in mitochondria

3. The intermediates formed during the oxidization of glucose should not participate in any biosynthesis process to form other products such as Amino acids, Purines pyrimidines or porphyrins.

4. The cellular respiratory substrate must only be GLUCOSE other substrates must not be considered.

Considering the dynamic nature of our cell and living system the above assumptions do not apply practically for a working cell. The balance sheet assumptions are theoretically accepted and followed.

Glucose Oxidation Respiratory Balance Sheet

When NADH produces 3 ATP and FADH2 produces 2 ATP

Respiration ProcessDirect SynthesisIn ETCATP ConsumedNet Gain
Krebs Cycle318+4Nil24
Acetyl CoA FormationNil6+NilNil6
Total Gain630+4-238

When NADH produces 2.5 ATP and FADH2 produces 1.5 ATP

Respiration ProcessDirect SynthesisIn ETCATP ConsumedNet Gain
Krebs Cycle215+3Nil20
Acetyl CoA Formation Nil5+NilNil5
Total Gain625+3-232

Under Anaerobic respiration, the pyruvic acid converts to lactic acid producing only 6 ATP.

The list of reactions which produced direct ATP synthesis and reduced equivalents are given below:

Glucose Oxidation: Glycolysis

1. Glyceraldehyde 3 Phosphate + NAD → 1,3 – diphosphoglycerate + NADH

Enzyme: Glyceraldehyde – 3 phosphate dehydrogenases

2. 1,3 diphosphoglycerate +ADP + Pi → 3 – phosphoglycerate + ATP

Enzyme: Phosphoglycerate Kinase

3. Phosphoenol pyruvate + ADP + Pi → Pyruvate + ATP

Enzyme: Pyruvate Kinase

These 3 reactions take place twice therefore they produce 4 ATP + 2 NADPH = 4 + 2 (3) = 10

Two other reaction consumes ATP

1. Glucose + ATP → Glucose 6 phosphate + ADP + Pi

Enzyme: Hexokinase

2. Fructose 6 Phosphate + ATP → Fructose1,6 diphosphate + ADP + Pi

Enzyme: Phosphofructokinase

ATP consumed is 2. Therefore, Glycolysis as a whole provides 8 ATP.

Under Anaerobic condition:

2Pyruvate + 2NAD → 2Lactate/ethanol + 2NADH → 6 ATP

Glucose Oxidation: Citric Acid Cycle

1. 2 Pyruvate + 2 NAD → 2 Acetyl Co – A + 2 NADH

Enzyme: Pyruvate Dehydrogenase

2. 2 Isocitrate + 2 NAD → 2 Oxalosuccinate + 2 NADH

Enzyme: Isocitrate Dehydrogenase

3. 2 α – ketoglutarate + 2 NAD → 2 Succinyl Co – A + 2 NADH

Enzyme: α – ketoglutarate Dehydrogenase

4. 2 Succinyl Co – A + 2GDP + 2Pi → 2 Succinate + 2GTP

Enzyme: Succinate Thiokinase

5. 2 Succinate + 2FAD → 2Fumarate + 2FADH2

Enzyme: Succinate Dehydrogenase

6. 2 Malate + 2 NAD → 2 oxaloacetate + 2 NADH

Enzyme: Malate Dehydrogenase

2 pyruvate molecules undergo complete oxidation and provide 30 ATP molecules.

Glucose Oxidation Citations


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