(3) Conversion of galactose and fructose. The liver is capable of converting
galactose and fructose to glucose. This is an important function, as the greater
proportion of the glucose that is formed by this method is usually released to the blood
by the liver and almost no other cells in the body can convert galactose to glucose.
b. Protein Metabolism. Protein metabolism is the most important metabolic
function carried on by the liver. If protein metabolism were to cease functioning, death
would occur within 48 hours.
(1) Deamination (breakdown) of amino acids. The deamination of amino
acids is necessary before they can be utilized either for energy or for conversion into
fats or carbohydrates. A very small amount of deamination occurs in the kidneys but it
is almost negligible. Almost all deamination required by the body is carried out by the
(2) Formation of urea for the removal of ammonia from body fluids. Large
amounts of ammonia are formed in the process of deamination. Without the formation
of urea by the liver for the removal of ammonia, the plasma ammonia concentration
would rise very rapidly and the result would be hepatic coma and death.
(3) Formation of plasma proteins. With the exception of part of the gamma
globulins, almost all of the plasma proteins are formed by the hepatic cells. Over 95
percent of the plasma proteins are produced by the liver. Plasma proteins can be
formed by the liver at a maximum rate of 50 to 100 grams per day.
c. Lipid Metabolism. Although fat (lipid) metabolism can take place in almost
all the cells in the body, it occurs so much more rapidly in the live. More than 60
percent of all fat metabolism occurs in the liver.
d. Vitamin Metabolism. The liver has the ability to store vitamins and to store
some of them in extremely large quantities. The vitamin stored in the largest quantity in
the liver is vitamin A. Sufficient amounts of vitamin A can be stored in the liver to
prevent a vitamin A deficiency for one or two years. Large quantities of vitamin D and
vitamin B12 are also stored in the liver.
213. HEMATOLOGIC FUNCTIONS
a. Fetal Blood Formation. During the third through the fifth month of
embryonic life, the liver forms most of the red blood cells and is, therefore, the principal
organ of erythropoiesis (red blood cell production). The liver begins to acquire this
function in the second month of fetal life and is totally functional by the third month.
From the third through the fifth month the liver produces nonnucleated red blood cells
which are of normal size. During the last three months of fetal life, red blood cells are
formed almost entirely by the bone marrow.