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Anabolism
Simpler molecules combining to form complex compounds is the
process involved in anabolism. Cells combine amino acids to form
structural proteins and functional proteins. Structural proteins
help repair and replace tissues. Enzymes, antibodies and hormones
are functional proteins that respectively catalyze chemical
reactions, help fight disease and regulate body processes.
During anabolism, cells convert glucose and
fatty acids to energy storage compounds. For instance, cells in the
liver and the muscles combine molecules of glucose to form a storage
compound known as glycogen. And cells in the fatty tissues combine
with fatty acids with glycerol to form body fat. Body fat can result
from a complex series of reactions involving excess glucose and
amino acids.
Catabolism
The breaking down of glucose, fatty acids and amino acids for
obtaining energy and heat is the process called catabolism. Here the
newly digested food, storage glycogen or body protein are the
compounds involved. The breaking down of fatty acids takes place
into two steps. In the first step, enzymes convert fatty acids into
acetyl coenzymes A. In the second step, the Acetyl-CoA enters a
series of chemical reactions known as Krebs cycle.
Similarly, glucose catabolism too goes
through two stages. The first step is called glycolysis. Glycolysis
works without oxygen. Glucose is broken down into pyruvic acid. A
small amount of energy is also released. If oxygen is present, the
pyruvic acid is converted to Acetyl CoA. The second stage then takes
place. This is the stage of the Krebs cycle. Here, a series of
chemical reactions combines Acetyl-CoA with oxygen to produce carbon
dioxide, water and energy.
Energy produced during catabolism
Around sixty per cent of the energy produced during catabolism
is heat. The remaining forty per cent is stored in the chemical
bonds that link atoms in a compound commonly referred to as ATP
(adenosine triphosphate). When required by the body, the energy
stored is broken and released by enzymes. |
