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Protein
Protein is any of a large group of naturally occurring
complex organic molecules containing nitrogen. A
molecule is a combination of atoms. An atom is the
smallest part of a substance that can exist alone or
in combination with something else. The word
"organic" means that the compound contains carbon,
a very common type of non-metallic element.
Nitrogen is a type of gaseous non-metallic element.
Protein is about 75% of the dry weight of most cell
matter.
Protein sources in food.
DESCRIBE PROTEIN STRUCTURE
Proteins are made of large combinations of amino acids (smaller types of chemicals),
usually 50 or more. As noted above, proteins contain nitrogen and carbon. Proteins also
contain other elements that are essential parts of human cells such as oxygen,
hydrogen, and occasionally sulfur, iron, iodine, and phosphorous.
WHY ARE PROTEINS & AMINO ACIDS IMPORTANT?
Protein can act as a source of energy and plays an important role in muscle
contractions, the response of the body's immune (defense) system, and other essential
life functions. Protein is the major source of building material for blood, muscles, hair,
skin, nails, and internal organs. Protein is also needed for the formation of many
hormones, antibodies, and enzymes. Hormones are types of chemicals in the body that
affect other cells. Antibodies are types of proteins that are formed by the body to destroy
foreign proteins known as antigens. Enzymes are types of proteins that help produce
chemical reactions in the body.
There are 22 amino acids known to be essential for proper growth, development, and
health maintenance. Remember that amino acids form proteins. The body can naturally
produce 13 amino acids, which is why these are called non-essential amino acids. The
other 9 amino acids are called essential amino acids because the body cannot produce
them and they must be obtained from diet.
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WHAT ARE GOOD PROTEIN FOOD SOURCES?
Good sources of protein are meat, poultry
(e.g., chicken), fish, milk, eggs, and cheese. Proteins
from these sources are known as complete proteins
because they complete the 9 essential amino acids (see
prior section). Incomplete proteins are those that do not
contain an adequate amount of all essential amino acids.
Sources of incomplete proteins include nuts, legumes
(e.g., beans), split-peas, and chick peas. Sources of
incomplete proteins include nuts, legumes (e.g., beans),
split-peas, and chick peas.
WHAT HAPPENS IF YOU CONSUME TOO LITTLE PROTEIN?
In children, too little protein results in abnormal growth and development of tissues, leading to
kwashiorkor (a type of malnutrition disease). In adults, too little protein results in fatigue and lack of
stamina, weakness, depression, slowed healing of wounds, poor resistance to infection, and slow
recovery from disease.
WHAT HAPPENS IF YOU CONSUME TOO MUCH PROTEIN?
In some conditions, consuming too much protein can result in fluid imbalance.
HOW IS PROTEIN ABBREVIATED?
Protein is sometimes abbreviated with a lowercase "p."
WHY IS IT CALLED PROTEIN?
Protein comes from the Greek word "proteios" meaning "first rank."