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Respiration requires organic molecules to be used as fuelThe starting molecule is usually glucoseIt is broken down in a series of stepsThis will give potential chemical energy
In the first step glucose is split
This stage is called glycolysis
In a series of enzyme controlled reactions two molecules of pyruvate are made
Pyruvate can stay in the cytoplasm and enter into the anaerobic pathway
This occurs in the absence of oxygen
If oxygen is present pyruvate enters the mitochondrionIt is converted to Acetyl CoA in the Link reaction
This molecule now enters the Krebs Cycle where NAD and FAD are reducedMost of the CO2 is made at this stage
The reduced molecules carry Hydrogen to the Electron transfer ChainThis generates ATP The final hydrogen acceptor is oxygen
Hydrogen Carrier Molecules
There are two of these in respiration
NADNicotinamide Adenine DinucleotideThis is a co-enzymeThis can accept electrons and hydrogen and become reduced
FADFlavin adenine dinucleotideIt is derived from Vitamin B2 (riboflavin)
FAD is more complex – all you need to know is it will carry hydrogen to the final stage of respiration
This is the splitting of sugar or more specifically glucoseIt takes place in the cytoplasm
6 Carbon glucose is split into 3 Carbon Pyruvate in a series of steps
ATP is used in the first steps but generated in the last few steps
NAD is reduced
In the first steps of glycolysis glucose has 2 phosphates attached
We say glucose is phosphorylated These are transferred from ATPSo two ATP molecules are usedA hexose biphosphate is made
We will tally the NAD reduced made here
We will keep tally of ATP here
This hexose phosphate is split into TWO triose (3C) phosphates
So from her onwards everything must be X2 for each molecule of glucose
Each triose phosphate then have a hydrogen removedThis is attached to NAD which becomes NADreduced
This is an energy yielding step – ADP is phosphorylated to ATP