Download Anaerobic Respiration

Anaerobic Respiration
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“anaerobic” = without oxygen
a way to obtain energy from nutrients without oxygen
this is done by repeating glycolysis and continuously making 2 net ATP (much less than
aerobic respiration which makes 36 net ATP)
During glycolysis…
GLUCOSE
2 NAD+
2 NADH
2 ADPto
2 ATP
- the cell does not directly require O2 for glycolysis,
- however, NAD+, needs to be regenerated for glycolysis
to continue.
- NADH is turned back into NAD+ when NADH gives its
electrons to the glycerol-phosphate shuttle to make
FADH2 in the matrix
2 PYRUVATE
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O2 is the final electron acceptor of the electron transport chain. It accepts electrons to
make H2O
If there is no O2 then, the ETC will become clogged with electrons because there won’t
be a molecule to accept the electrons
As a result, the ETC will not be free to oxidize the coenzymes NADH and FADH2
o Thus protons will not be pumped into the innermembrane space and thus a
proton motive force will not be created to produce ATP
o and FAD will not be regenerated to pick up the electrons from the NADH made
in glycolysis
o as a result, the NADH in the cytoplasm will not be turned back into NAD+, and so
glycolysis won’t continue.
Organisms have evolved a way of recycling NAD+ and continuing glycolysis without O2
Electrons of NADH will be transferred to organic molecules instead of the ETC.
The process is called FERMENTATION
o 1. ethanol formation
o 2. lactic acid formation
1) Ethanol Fermentation
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NADH transfers hydrogen atoms to acetaldehyde
Acetaldehyde is converted into ethanol and in the process NADH is oxidized to NAD+ so
glycolysis can continue
In this way, 2 ATP is continuously made to meet energy needs
Ethanol fermentation is carried out by yeast
Yeast: unicellular fungus that is found in habitats where glucose/sugars are available
o Can undergo anaerobic or aerobic respiration.
o Used to make breads, pastries, wine, beer, liquor, soy sauce, bioethanol….
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Ex: Baking Bread
o Live yeast cells are mixed with starches (in flour) as the dough is kneaded
o Yeast will break down the glucose in start through cellular respiration
o Any oxygen in the dough will be used up in aerobic respiration
o Now without O2, the yeast ferments the glucose in starch to make CO2 and
ethanol
o The CO2 produced will not be able to escape and thus will form bubbles making
the bread rise
o The ethanol evaporates when bread is baked
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Ex: beer, wine making
o Yeast ferments sugars in fruit juices
o Fermentation ends when ethanol concentration is ~12% because this
concentration will kill the yeast cells.
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Ex: Bioethanol
o Bioethanol: Ethanol produced by living organisms as a renewable energy source.
o Yeast can be used to produce bioethanol from sugar cane and maize
o After the ethanol is produced, it is purified by distillation and other methods to
remove the water
o Bioethanol can be used as a fuel in vehicles
2.) Lactic Acid Fermentation
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during strenuous exercise, breakdown glucose faster than O2 can be supplied
lactate fermentation takes over
Lactic Acid Fermentation allows for ATP to be made very rapidly for a short period of
time.
NADH gives its electrons to pyruvate to make lactate (lactic acid)
Lactic acid is actually poisonous to our cells.
There is a limit to how much our cells can withstand which limits how much anaerobic
respiration the body can do.
The accumulation of lactic acid in muscles cause stiffness, soreness, and fatigue.
When exercise stops, lactate is converted back to pyruvate for aerobic respiration by the
liver.
VO2 Max and the Lactate Threshold
Aerobic Fitness: a measure of the ability of the heart, lungs, and blood stream to supply O2
to the cells of the body during physical activity.
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Muscle cells need ATP to contract
ATP production should increase if more O2 absorbed
VO2 max = maximum oxygen consumption.
- It’s a measurement of the body’s capacity to generate energy required for physical
activity.
- Maximum volume of O2 in mL the cells of the body can remove from the blood
stream In 1 minute per kilogram of body mass.
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Individuals with a high VO2 max values are considered more aerobically fit.
Average VO2 max for North Americans ~ 35mL/kg/min
Average VO2 max for athletes ~70mL/kg/min
VO2 max values may be increased with exercise and training but is also affected by
genetics.
Values with decrease with age.
There isn’t always a correlation between VO2 max and athletic performance.
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As you exercise, lactate increases because O2 is not available for all the cells.
As exercise intensity increases, lactate levels increase
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Lactate Threshold
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Value of exercise intensity at which [blood lactate] increases sharply because lactate
production is greater that lactate removal.
Exercising below this intensity can be maintained for hours (such when someone is
running a marathon)
However, beyond this may limit duration b/c of pain, stiffness, fatigue
Athletic training improves blood circulation an increases the efficiency of O2 delivery to
body cells
This results in an increase in lactate production during exercise and an increase in the
lactate threshold.
 can sustain greater exercise intensities.
Lactate Threshold for Untrained athletes: 60%
VO2 max
Lactate Threshold for Elite athletes: 80% VO2
max