Revision:Anaerobic Respiration

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Glycolysis of 1 glucose molecule

• occurs in the cytoplasm

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

• 2 molecules of NAD⁺ reduced to 2NADH + H⁺

(transferred to electron transport system; in cardiac muscle and liver cells, it is first accepted by the the electron acceptor , NAD⁺ when it enters the ETS and in 3 points of the ETS, energy released by oxidation is sufficient to create ATP molecule from oxidative phosphorylation. This explains why in cardiac muscle and liver cells, only 36 ATP are produced instead of 38 ; in skeletal muscle and nervous tissues, it is first accepted electron acceptor in ETS, Coenzmye Q and only in 2 points where the energy released by oxidation is sufficient to create ATP molecule from oxidative phosphorylation. This explains why in skeletal muscle and nervous tissue, 38 ATP are produced). NADH + H⁺ produced in glycolysis has to be transferred to the mitochondrion to enter ETS from cytoplasm. This is where it differs from the NADH + H⁺ produced in Link's reaction and Kreb's cycle where they directly enter the ETS with each producing 3 ATPs.

• 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 substrate-level phosphorylation (the substrate is GTP which transfers one of its phosphate groups to ADP)

• 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 (formation of ATP that uses energy released from oxidation of NADH + H⁺ and FADH2.

• 2 molecules of ATP are produced from each FADH2 molecule

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

• Net number of ATP molecules produced is 38 ATP for each glucose molecule.

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