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Respiration is the process by which chemical energy stored in glucose is converted to chemical energy
stored in ATP.

Glucose + Oxygen Carbon Dioxide + Water
C6H12O6 + O2 CO2 + H2O

The Mitochondria

Much of respiration takes place in the mitochondria.

Mitochondria have a double membrane: the outer

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Glycolysis is the initial stage of both aerobic and anaerobic respiration.

It occurs in the cytoplasm of all living cells and is the process by which a hexose sugar, usually glucose,
is split into two molecules of the 3-carbon molecule, pyruvate.

There are four stages:

Activation of glucose by…

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The pyruvate molecules produced during glycolysis possess potential energy that can only be
released using oxygen in a process called the Krebs cycle.

Before they enter the Krebs cycle, these pyruvate molecules must first be oxidised in a procedure
known as the link reaction take place exclusively inside mitochondria.


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The Krebs cycle involves a series of oxidation-reduction reactions that take place in the matrix of the

1. A 2 carbon acetylcoenzyme A from the link reaction combines with a 4 carbon molecule to produce
a 6 carbon molecule

2. This 6 carbon molecule loses carbon dioxide and hydrogen…

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Hydrogen atoms and the electrons they possess are a valuable source of energy.
These hydrogen atoms are carried by coenzymes NAD and FAD into the next stage of the process: the
electron transport chain.

This is the mechanism by which the energy of the electrons within the hydrogen atoms is…

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If there is no oxygen (anaerobic conditions) then the final reaction to make water cannot take place.
Electrons can't leave the respiratory chain, and so NADH cannot unload any hydrogens to the
respiratory chain.

This means that there is no NAD in the cell; it's all in the form of…

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Summary of respiration to see how much ATP is made from each glucose molecule.
ATP is made in two different ways:

· Some ATP molecules are made directly by the enzymes in glycolysis or the Krebs cycle. This is called
substrate level phosphorylation (since ADP is being phosphorylated to form…


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