Transcript anaerobic-resp

Higher Biology
Anaerobic Respiration &
Alternative Substrates
Anaerobic respiration
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In animal cells:
In the absence of oxygen
Glucose (6C)
pyruvic acid (3C)
Krebs cycle
O2 debt repaid
Lactic acid (3C)
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This reaction is reversible since there is no loss of
carbons (as CO2).
Anaerobic respiration
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In plant and yeast cells:
In the absence of oxygen
Glucose (6C)
pyruvic acid (3C)
ethanol (2C) + CO2
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This reaction is irreversible since there is a loss of
carbons (as CO2).
This process is also called fermentation.
Anaerobic respiration
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In the absence of oxygen there is only
partial breakdown of glucose and less
energy produced.
For 1 molecule of glucose only 2 ATP are
released (compared to 38 ATP in aerobic
respiration)
Anaerobic respiration is much less
efficient than aerobic respiration.
View the ANIMATION 5.5
Alternative Substrates
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A respiratory substrate is any substrate that can
be broken down to release energy.
Fatty acids are formed from the digestion of fat in
food.
They can be converted into Acetyl CoA in the
matrix of the mitochondria.
The Acetyl CoA then enters the Krebs cycle.
The use of fatty acids results in twice the energy
compared to the same quantity of carbohydrate.
Alternative Substrates
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Excess Amino acids (from proteins) are broken
down in the liver.
The amine group is converted into urea and
excreted by the kidney.
The remaining carbon skeleton can be used as a
respiratory substrate.
It can be converted into pyruvic acid which is then
converted into Acetyl CoA.
The Acetyl CoA then enters the Krebs cycle.
Excess protein from the diet always provides a
certain amount of energy.
Only in extreme conditions, such as starvation, is
tissue protein used as an energy source.
Alternative Substrates
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On your Respiration Summary mark where
fatty acids and amino acids would enter
the process.
Measuring the rate of respiration
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Practice Questions
From the Torrance textbook:
1. TYK page 30 Q2 & 3
2. AYK page 30 Q1, 3, 5 & 6.