Summary of Chapter 5 – Proteins and Amino Acids
Chemically speaking, proteins are more complex than carbohydrates or lipids; proteins are made of some 20 different amino acids, 9 of
which the body cannot make (they are essential). Each amino acid contains a central carbon atom with an amino group, an acid group, a
hydrogen atom, and a unique side group attached to it. The distinctive sequence of amino acids in each protein determines its shape and
function.
Functions of proteins in the body include:

Enzymes. Proteins facilitate chemical reactions.

Fluid and electrolyte balance. Proteins help to maintain the distribution and composition of various body fluids.

Acid-base balance. Proteins help maintain the acid-base balance of body fluids by acting as buffers.

Antibodies. Proteins act against disease agents to fight diseases.

Hormones. Proteins regulate body processes. Some, but not all, hormones are made of protein.

Transportation. Proteins transport substances such as lipids, minerals, and oxygen around the body.

Growth and maintenance. Proteins form integral parts of most body structures such as skin, tendons, ligaments, membranes,
muscles, organs, and bones. As such, they support the growth and repair of body tissues.

Energy. Proteins provide some fuel for the body’s energy needs.
This list of protein functions is by no means exhaustive. Nevertheless, it does give some sense of the immense variety of proteins and
their importance in the body.
Protein deficiencies arise from both energy-poor and protein-poor diets and lead to the devastating diseases of marasmus and
kwashiorkor. Together, these diseases are known as PEM (protein-energy malnutrition), a major form of malnutrition causing death in
children worldwide. Excesses of protein offer no advantage; in fact, overconsumption of protein-rich foods may incur health problems as
well.
Normal, healthy people do not need amino acid or protein supplements. Optimally, an adult’s diet will be adequate in energy from
carbohydrate and fat and will deliver at least 0.8 grams of protein per kilogram of healthy body weight each day.
A diet inadequate in any of the essential amino acids limits protein synthesis. The best guarantee of amino acid adequacy is to eat foods
containing high-quality proteins or combinations of foods containing complementary proteins so that each can supply the amino acids
missing in the other. Vegetarians who consume no foods of animal origin can meet their protein needs by eating a variety of whole
grains, legumes, seeds, nuts, and vegetables.