RESPIRATION-(higher
level)
Glycolysis Glycolysis Animations
The
Krebs Cycle Electron
Transport Aerobic Respiration Animations
Using
ATP Anaerobic
Respiration Lactic Acid
Alcohol
Fermentation Anaerobic Respiration Summary
Biotechnology Immobilised Cells
Please
read through the Respiration-ordinary
level web page to get an introduction to this topic.
Glycolysis takes place
in the cytosol.
The cytosol is the clear portion
of the cytoplasm. Here is where the enzymes needed for stage 1 are located. This process does not need oxygen.
The process of
glycolysis functions to split a glucose molecule into two 3-carbon molecules called pyruvic
acid (C3H4O3). Pyruvic acid is a neutral particle. It may also be found as a negatively charged ion called pyruvate. The energy released
is used to form 2 ATP molecules + water + 2 NADH molecules.
As stated previously
in the ordinary level web page, if there is no oxygen available then anaerobic
respiration takes place.
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IF OXYGEN
IS PRESENT:
If oxygen is
present the pyruvic acid enters the mitochondria. (Recall that glycolysis
occurs in the cytosol of the cell.)
Here it loses a carbon dioxide molecule and forms a 2-carbon molecule called acetyl coenzyme A (CoA). While forming
acetyl CoA it loses two high energy electrons and a proton. These are used to
form NADH. The NADH then goes to the
electron transport system. (will be
discussed later) If oxygen is not
present anaerobic respiration takes place.
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Click
here to view an interactive animation of glycolysis
Click
here to view animation #1 of glycolysis
Click
here to view animation #2 of glycolysis
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The acetyl CoA
now undergoes changes called the Krebs
Cycle. The acetyl CoA is broken down to carbon
dioxide
and protons (H+). The energy
contained in the acetyl CoA is released in the form of high energy electrons.
The
electrons and protons are picked up by NAD+ to form NADH. The NADH goes
into the electron transport system.
(will be discussed later) Also phosphorylation
occurs where a phosphate group is added to ADP to form ATP.
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STAGE 2- THE
ELECTRON TRANSPORT SYSTEM
The electron transport
system happens in the inner membrane
of the mitochondria. Remember that Stage
1 (glycolysis) occurs in the cytosol of the cell.
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The
electron transport system is
composed of a series of proteins that transfer
NADH from protein to protein.
With each transfer to a new protein some of the energy in the NADH is released to form ATP. This is done by oxidative phosphorylation. Refer to the
Energy
for Life web page to review oxidative phosphorylation.
At the end of the electron transport system electrons are used to combine hydrogen with oxygen to form water.
If there is no oxygen present the electron transport system cannot operate and
therefore the organism will die as a
result of the lack of energy (ATP) production.
3 Animations of electron transport
in Mitochondria:
Animation 1:
1. Protons are moved across the membrane,
from the cytosol to the intermembrane space.
2. Electrons are transported along the
membrane, through a series of protein carriers depicted as “Q” and “cyt C” in the
diagram.
3. Oxygen is the final electron acceptor,
combining with electrons and H+ ions to produce water.
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Animation 2:
Recall
that a molecule is reduced when it
gains and electron and it is oxydized when
it loses an electron.
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Animation 3:
NADH and carries protons (H+) and electrons
(e-) to the electron transport chain located in the membrane. At the
end of the electron transport system, two protons, two electrons, and half of
an oxygen molecule combine to form water.
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Animation of ATP formation
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ADP combines with a phosphate group to form ATP.
The ATP Synthase is the enzyme
used in this process.
Click
here to view an animation of electron transfer and ATP formation
To obtain
energy to do cellular work, the cell enzymatically removes the third phosphate
from ATP thus releasing the stored energy and forming ADP and phosphate once
again.
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Aerobic Respiration Links
ANAEROBIC RESPIRATION (ordinary level)
In anaerobic respiration
oxygen is not needed although it can take place in the presence of oxygen. In
anaerobic respiration glycolysis
takes place. The 3-carbon molecules (pyruvic acid) are then converted into
other products. Anaerobic respiration is also known as fermentation.
Two products of anaerobic respiration
are lactic acid and alcohol.
Lactic acid is produced in
some bacteria, fungi, and muscle tissue.
Pyruvic Acid is changed into lactic
acid + small amount of energy
Pyruvic Acid is changed
to Lactic Acid + energy (ATP)
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Examples of Lactic Acid:
Bacteria causing milk to sour
Bacteria change cabbage to sauerkraut
Bacteria changing dairy products to cheese and yoghurt
Build up of lactic acid in muscles (because of lack of oxygen)
causing cramps and stiffness
Alcohol fermentation occurs in
some bacteria, yeasts, and in plants deprived of oxygen. Again the pyruvic acid
formed by glycolysis is changed. Here it is changed into ethanol ethyl alcohol) and carbondioxide.
Pyruvic Acid is changed into ethanol +
small amount of energy
Pyruvic Acid is changed to Alcohol +
Carbon Dioxide + energy (ATP)
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Uses of Alcohol Fermentation
Baking:
the carbon dioxide causes the dough to rise
Beer
and Wine production
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(See batch
processing and continuous flow processing by clicking on the Bacteria
Webpage on the Homepage)
Just as enzymes are immobilised for
commercial uses bacteria, fungi, and yeasts are also immobilised for production
of products. See the enzyme webpage to review
immobilisation techniques.