Answer to Question #9081 in Biochemistry for Daisy

Question

Explain how an animal that persists on a diet composed of 90% protein, 7% fat, and 3% carbohydrate utilizes food of this composition to maintain itself and grow

Answer 1

This diet is unusual for animals and results in numerous changes
in
metabolism. Carbohydrates (a usual source of energy for animal)
are
very few in this diet, thus carbohydrates cannot serve as a
major
energy source. Thus, energy is extracted from proteins. 1g of
protein
contain almost the same amount of energy as 1g of
carbohydrates,
however digestion of proteins is much more difficult. In the
stomach
and intestine proteins are split to aminoacids; this aminoacids go
to
every cell of the organism through the blood. Decomposing of
aminoacids
involves complicated system of chemical reactions, the
central part of this
reactions is citric acid cycle. Most of
aminoacids are splitted to acetyl-CoA
and during this process give
energy in form of ATP and NAD(P)H. Next,
acetyl-CoA molecules can
serve as a source of energy (in the citric acid
cycle) or can be used
as building blocks for creating lipids and
carbohydrates that are
necessary for organism. Thus, in this case proteins
perform functions
normally attributed to carbohydrates and lipids. Finally,
lipids from
food become building blocks for steroid hormones, eicosanoids
and
specific intra-cellular lipids.