Hydrolysis of Fats|
Glycerol to Acetyl CoA
Fatty Acid Spiral
Citric Acid Cycle
Electron Transport System
Metabolism of Fats
In this section we will consider one of the primary aspects of the metabolism of
fats--their use as a source of energy.
Oxidation of Fats
|The overall reaction can be summarized by this equation.
O2 + fat CO2 + H2O +
|In it oxygen combines with the fats to make carbon dioxide
and water and release the energy that is needed by our bodies or any living thing to do
the things that it needs to do. However, the process is much more involved than that.
|Consider that a particular fat molecule may have 58 carbons, 112 hydrogens
and 6 oxygen atoms in it.
O2 + C58H112O6
CO2 + H2O
|Also consider what has to happen in order to convert that fat
molecule into carbon dioxide and water. You must separate those 58 carbons from one
another. You must separate the hydrogens from the carbon atoms. You must break the oxygen
molecule apart. Then you must to recombine all those atoms to make CO2 and H2O.
It shouldn't be a surprise that a process like that might take hundreds of smaller
individual reaction steps.
Even though you do now know quite a bit of chemistry, you will not be held responsible
for knowing all of those steps. However, you should be able to make sense of them and be
able to identify the kinds of reactions that are involved in each of those steps, when you
are shown what those steps are.
Let me give you an overview of the process that occurs in taking fats to carbon dioxide
and water. (This is also shown in Example 8 in your workbook.)
|The fats are broken down by hydrolysis reaction to form glycerol
and fatty acids. Glycerol is oxidized to form pyruvic acid
(both have three carbon atoms). The pyruvic acid is converted to a compound called acetyl
CoA, which only has two carbon atoms in the acetyl part thus giving off carbon
dioxide. In the process of losing a carbon atom, the pyruvic acid also combines with
something called coenzyme A.
|Meanwhile, the fatty acids are also
converted into acetyl CoA by means of a series of chemical reactions. The
acetyl CoA is then combined with another chemical called oxaloacetic acid to form citric
acid. Then a sequence of reactions occurs in which the oxaloacetic acid is
regenerated and then converted back in to citric acid by more acetyl CoA. This cyclic
process is known by several names: the citric acid cycle, the Krebs
cycle, the tricarboxylic acid (TCA) cycle.
At a couple different steps in this process, carbon dioxide is generated. Also, at
several different steps, hydrogen atoms are removed from the molecules and those hydrogen
atoms are then subsequently allowed to react with oxygen to form water. So in the process
of the oxidation of fats, the oxygen actually comes into the process quite late.
Next, let's consider each of the portions of the overall process in turn: hydrolysis
of fats, glycerol to acetyl CoA, fatty acid spiral
(to acetyl CoA), citric acid cycle, and electron transport system
(oxygen finally gets the electrons).
Top of Page
19600 South Molalla Avenue
Oregon City, OR 97045
(503) 657-6958 x 2778
TDD (503) 650-6649
Distance Learning questions
Clackamas Community College
©2001, 2003 Clackamas Community College, Hal Bender