From The Student Room

TSR Wiki > Study Help > Subjects and Revision > Revision Notes > Biology > Anaerobic Respiration

---

Contents 1 Glycolysis 1 glucose molecule 2 Link Reaction Pyruvate Oxidation 3 Krebs Cycle 4 Electron Transport System 5 Comments

Glycolysis 1 glucose molecule

• 2 molecules of ATP (4 created-2 used)

• 2 molecules of NAD⁺ reduced to 2NAD +2H⁺ (transferred to electron transport system).

• 2 molecules of pyruvate 2x3carbons (they enter Link Reaction)

Link Reaction Pyruvate Oxidation

• Occurs in the matrix of mitochondria.

• Pyruvate combines with coenzyme A to form acetyl coenzyme A.

In the process a molecule of CO₂ and 2H are removed.

The hydrogen atoms are transferred to the Electron Transport System.

The 2C acetyl coenzyme A disassociates forming coenzyme A acetate which enters the Krebs Cycle.

Krebs Cycle

Acetyl coenzyme A from Link Reaction is used to make:

• 3 molecules of NAD⁺ reduced to NADH + H⁺

• 1 molecule of FAD reduced to FADH₂

• 2 molecules of CO₂

• 1 molecule of ATP by phosphorylation

• Oxaloacetate is regenerated to start cycle again.

The most important part of the Krebs Cycle is the release of hydrogen ions to be used in the Electron Transport System for generation of ATP.

Electron Transport System

• Occurs on the inner membrane of mitochondrion

• Converts energy in form of hydrogen to ATP.

The hydrogen ions received from the Krebs Cycle are attached to hydrogen carriers (NAD and FAD) which are reduced.

As reduced NAD and FAD are passed along the electron transport chain, the hydrogens are removed and the hydrogen atoms split into:

• Hydrogen ion H⁺ (proton)

• Electron e^-

At the end of the system the hydrogen ions and electrons recombine and are then used to reduce oxygen to form water.

The formation of ATP through the oxidation of hydrogen atoms is called Oxidative Phosphorylation.

• 2 molecules of ATP are produced from each FADH2 molecule

• 3 molecules of ATP are produced from each NADH + H⁺ molecule

Stage in Aerobic Respiration	ATP Produced	ATP Used	NADH + H+ produced	FADH2 produced
Glycolysis	4	2	2	0
Link Reaction	0	0	2	0
Krebs Cycle	2	0	6	2
Electron Transport System	30(NADH +H+) 4(FADH2)	-	-	-
Total	40	2	10	2

Comments