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Transcript
anaerobic respiration
Why?
At the start of intense exercise, oxygen demand inevitably exceeds oxygen provision.
Therefore, with O2 to accept the hydrogen and the electrons at
the culmination of the electron transport chain, oxidative phosphorylation ceases and the NADH + H+ produced by glycolysis,
the link reaction and the Krebs cycle isn’t oxidized. Without this
oxidation, which provides NAD, the respiration reactions cannot
continue.
The work around
The NADH + H+ from glycolysis can be oxidized without O2 to create! This is achieved by the reduction of pyruvate to lactate, which
allows the oxidation of the NADH + H+ to NAD.
However, although this allows respiration to continue without O2,
it is very inefficient, creating just 2 molecules of ATP per glucose
molecule, as opposed to the 38 allowed by aerobic respiration.
The result
The build up of lactate leads to the creation of lactic acid, which
leads to the pH of the cell falling dramatically. This inhibits enzyme
catalysed reactions- including glycolysis, as the positive H+ ­ions
gum up the negatively charged groups in the active site of the
enzyme.
Therefore, an oxygen debt has been created; also known as
post-exercise oxygen consumption. After exercise, oxygen
is used to convert the lactate back to pyruvate, where it is
oxidised into CO2 and water via the krebs cycle, releasing ATP.
Some lactate may also be converted into glycogen and stored
in the liver.
ATP/PC system
This is what is actually used initially in any sort of exercise; it
only lasts for 6-10 seconds. It avoids respiration entirely by using creatine phosphate (or phosphocreatine, PC) to regenerate ATP:
Creatine phosphate --> creatine + pi
ADP + Pi --> ATP
Therefore :
ADP + Creatine Phosphate --> ATP
This is known as the ATP/PC system, and is used for very
short, intense periods of exercise such as throwing, lifting or
sprinting. The creatine phosphate stores are then regenerated
later, when the body is at rest.
Therefore, we have three energy systems acting at different
times:
1. ATP/PC system provides ATP for the first 10 seconds
2. Anaerobic respiration (glycolysis) will keep you going for
another couple of minutes
3. Aerobic respiration is the main contributor in sports which
require more than a few minutes of continuous exertion.
Archy de Berker
date: