From The Student Room

TSR Wiki > Study Help > Subjects and Revision > Revision Notes > Biology > Digestion Revision Questions (A Level)

Glycolysis is an anaerobic process that occurs in the cytoplasm.

Glucose (6C) is split into two molecules of pyruvic acid (2 x 3C).

The hydrogen released during glycolysis binds to the coenzyme (hydrogen acceptor or carrier) NAD (nicotinamide adenine dinucleotide) to form NADH2.

The NADH2 is available for ATP production in the final stage of cellular respiration.

Two molecules of ATP are required to convert glucose to pyruvic acid. Four molecules of ATP are produced by glycolysis (a net gain of two ATP molecules).

The Krebs cycle is an aerobic process that occurs in the matrix of the mitochondrion.

Pyruvic acid (3C) is initially converted to acetyl CoA (2C), with the release of CO2.

NADH2 is also produced, and is available for ATP production in the next stage of cellular respiration.

Acetyl CoA binds to an intermediate 4C molecule to form citric acid (6C).

Citric acid is converted through a series of enzyme-catalysed reactions back into the 4C molecule.

In the process, both carbon (in the form of carbon dioxide) and hydrogen are released.

Hydrogen becomes bound to NAD to form NADH2. This will be used in the next stage of respiration for ATP production.

Hydrogen transfer through the cytochrome system is an aerobic process and occurs on the surface of the cristae of the mitochondrion.

The hydrogen from NADH2 is transferred to the cytochrome system where energy is released and used in the production of ATP (oxidative phosphorylation).

Three molecules of ATP are made from each molecule of NADH2.

Oxidative phosphorylation results in the formation of 36 ATP molecules from one molecule of glucose.

Oxygen is the final hydrogen acceptor in the cytochrome system, forming water.

The bold parts relate to ATP, and the italic bold parts are specifically to do with the number produced.

Comments

These notes were originally written by Reverie. in this thread on TSR Forums.