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RESPIRATION
Glycolysis
There are two different forms of cellular respiration depending on whether oxygen is
involved or not:
● Aerobic respiration- requires oxygen and produces carbon dioxide, water and
much ATP
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Aerobic respiration can be divided into 4 stages:
1
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Link reaction- the 3 –carbon pyruvate molecules enter into a series of
reactions which lead to a formation of acteylcoenzyme A, a 2-carbon
molecule
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Krebs cycle- the introduction of acetylcoenzyme A into a cycle of
oxidation-reducton reactions that forms some ATP and a large quantity of
reduced NAD and FAD
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Oxidative ohosphorylation- the use of electrons, associated with reduced
NAD and FAD, released from Krebs cycle to synthesis ATP with water
produced as a by-product
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Does not need oxygen to take place- so
it is an anaerobic process
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glucose is phosphorylated using a phosphate from a molecule of ATP, which
hydrolysis into ADP and phosphate
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This provides energy to activate glucose and lowers activation energy (Ea)
3
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Triose phosphate loses hydrogen and forms 2 molecules of pyruvate
2
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4 ATP produced, but 2 were used up in stage one, so there is a net gain of
2ATP
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● The pyruvate is oxidised to acetate
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These hydrogens are accepted by
NAD to for reduced NAD
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Pyruvate+ NAD+ CoA→acetyl CoA+ reduced NAD +CO​2

The Krebs cycle
It takes place in the matrix of mitochondria
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Fatty acids-broken down to acetates anter the krebs cycle via CoA
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● The 2 carbon acetylcoenzyme A from a link reaction combines with a 4carbon molecule to produce a 6-carbon molecule
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Coenzymes
A coenzyme is a molecule that aids the function of an enzyme
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● NAD, WHICH IS IMPORTANT THROUGHOUT RESPIRATION
● FAD, WHICH IS IMPORTANT IN THE KREBS CYCLE
● NADP, WHICH IS IMPORTANT IN PHOTOSYNTHESIS
The significance of Krebs cycle
● It breaks down macromolecules into smaller molecules such as pyruvate or
carbon dioxide
● Manufacture of other products such as fatty acids, amino acids and
chlorophyll
● It produces hydrogen atoms that are carried by NAD to the electron transfer
chain and provide energy for oxidative phosphorylation
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Oxidative phosphorylation
1
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The H atoms split into protons (H+) and electrons
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The electrons move down the electron transport chain, losing energy at each
electron carrier
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This energy is used by the electron carriers to pump protons fro the matrix into
the intermembrane space
4
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5
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ATP forms
6
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This means oxygen is the
final electron acceptor
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Lipids are first hydrolysed to glycerol and fatty acids
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The fatty
acids are broken down into two carbon fragments which are converted to acetyl CoA
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Because a lot of H-atoms are produced which are used to make ATP
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Protein is hydrolysed into amino acids
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