Proteins are essential components that are required for growth, repair, and maintenance of tissues. They are made up of amino acids, including eight essential amino acids that must be obtained through diet. Proteins are classified based on their amino acid content as complete, partially complete, or incomplete. Complete proteins from animal sources contain all essential amino acids, while plant proteins are typically partially complete or incomplete. Consuming complementary plant proteins can improve their nutritional value. Proteins are needed for many important bodily functions and a deficiency can lead to health issues.

1. Created By
PRABAL MUKHERJEE
LECTURER
INDIAN HOTEL
ACADEMY

2. PROTEIN
Protein has been derived from a Greek word meaning to take first place, as it is the most abundant component of
protoplasm presents in all cells.
All the amino acids are essential units for the synthesis of the protein molecule. However, the body can produce many
amino acids if it has an adequate nitrogen source, but cannot produce certain others in adequate amounts to meet body
needs. These amino acids, which can not be synthesised in required amount by the body. From the nutrition stand point,
they form the critical components of the dietary protein.
There are eight essential amino acids required by adults. These are Methionine, Tryptophan, Threonine, Valine, Isoleucine,
Leucine, Lysine, Phenylalanine and Histidine.

3. PROTEIN
CLASSIFICATION OF PROTEINS
Proteins are classified on the basis of their amino acid contents, which determines their quality.
 Complete [proteins are first class proteins : These proteins contain all essential amino acids in proportion capable of
promoting growth when they are the only source of protein in the diet. They are also known as high biological value
proteins. All animal proteins except gelatine are complete proteins.
 Partially Complete or second class proteins : These generally lack in one to few of the essential amino acids. In
contrast to complete proteins, if these are used as the sole source of protein in the diet, they will not provide all the
essential amino acids necessary for the synthesis of body proteins. Most vegetable proteins fall in this category.

4. PROTEIN
 Incomplete proteins or third class proteins : These proteins are not capable of
allowing even repair and maintenance of the body tissues. Gelatine is the main
example. Proteins are extremely complex compounds of carbon, hydrogen,
oxygen and nitrogen and may contain elements like iron, sulphur, zinc, iodine,
copper, phosphorus etc. These elements are present in the protein in the form of
building units, known as amino acids. Food protein contains about twenty
amino acids.

5. PROTEIN
Protein Quality
The quality of protein depends on the number and extent of essential amino acids present in it. If a protein contents
all essential amino acids iin sufficient quantities to maintain body tissues and to promote a normal rate of growth, it
is known as good quality protein. Animal proteins are first class proteins but all are not equally good in meeting
growth requirements, although none of them is totally lacking in essential amino acids.
Plant proteins are partially complete in nature., as they may contain all essential amino acids but have a relatively
small amount as compared to its requirements and such amino acids are called limiting amino acids.

6. PROTEIN
These proteins can allow maintenance of body tissue, but they do not have enough essential amino acid to promote growth. The various examples
are proteins present in cereals as lysine, which is the limiting amino acid. In cereals, pulses and nuts, the limiting amino acid is methionine.
Supplementary value of proteins :
It means of improving the quality of mixed protein in the diet. If two suitable vegetable proteins are taken together, they will complement one
another, for example a combination of wheat lacking in lysine, but plentiful of methionine and a pulse limiting in methionine but containing lysine
would provide a mixture containing all essential amino acids. This is also known as mutual supplementation.

7. PROTEIN
On the other hand, the incomplete protein like wheat can also be supplemented with a small
amount of good quality of animal protein such as milk which would provide the missing
amino acid lysine would enhance the biological value of wheat protein.
Complete or first class protein
Complete protein contains all essential amino acids in sufficient quantities to maintain tissues
and promote a normal rate of growth, for example, all animal proteins except gilatine.

8. Biological Value of protein is a measure of protein quality and is as the percentage of absorbed dietary
nitrogen that is actually retained in the body when that protein is the only source of nitrogen in the
body. Partially complete proteins are only from plant kingdom.
These generally lack one or two essential acids or many contain all essential amino acids but have a
relatively small amount of one as compared to its requirement and such amino acids are called
limiting amino acid. These can allow repair and maintenance but not growth. Cereal provides lack in
lysine but pulse proteins lack inn methionine.

9. FOOD SOURCES OF PROTEIN
ANIMAL FOODS :
 Meat
 Fish
 Egg
 Cow Milk
 Cheese
 Whole/skimmed Milk Powder

10. FOOD SOURCES OF PROTEIN Fenugreek Leaves
PLANT FOODS : Mint
 Pulses Broad beans
 Soybean Peas
 Peanuts Rice (Parboiled, hand pounded)
 Whole Wheat
 Rice (raw, milked)
 Amaranth

11. PROTEIN
FUNCTIONS OF PROTEINS
Although we rely on protein rich foods as a source of amino acids, the essential amino acids are the ultimate nutrients for the
body. The various functions performed by proteins are:
 Essential for Growth, Repair and Maintenance of Tissues : Proteins are the most abundant solid components of protoplasm
and hence of muscles, organ matrix of bone and teeth, skin, nail and hair, blood cells and serum. Even all living cells, all body
fluids except urine and bile, contain protein. Hence proteins are required for the important functions of growth, repair and
maintenance.

12. PROTEIN
FUNCTIONS OF ESSENTIAL BODY COMPOUNDS:
 Hormones, such as Insulin and Thyroxine are protein in nature
 All enzymes are protein and catalyse digestion or metabolic reactions in the body.
 Haemoglobin, the blood pigment, is responsible for carrying oxygen and carbon dioxide in cell respiration and is a protein complex.
 Most of the blood clotting substances are proteins.
The compounds responsible for vision, are also proteins
The amino acid Tryptophan acts as a precursor for Niacin, which has regulatory function as a vitamin.

13. PROTEIN
REGULATION OF WATER BALANCE
Proteins along with electrolytes, such as sodium, exert the osmotic pressure to draw the fluid into
the vascular system. When the level of plasma protein is low, the water is not drawn back into the
circulatory system. Proteins are accumulated in the inter cellular spaces, making the tissue
oedematous, a condition in which liquid collects in the spaces inside the body and makes a swell.

14. PROTEIN
MAINTENANCE OF BODY NEUTRALITY
Proteins are considered amphoteric substance or buffers, capable of reacting with either acids or bases to neutralize them. Blood proteins
perform an important function in helping to maintain body neutrality essential for normal cellular metabolism.
STIMULATION OF ANTIBODY FORMATION
The antibodies responsible for the body’s ability to combat infections, are protein substances. These are produced in response to specific
infective agent.
The ability to detoxify poisonous materials in the body is controlled by enzymes those are protein in nature located primarily in the liver.
Proteins are also capable of providing energy to the body by giving 4calories/gm

15. PROTEIN
The energy needs of the body takes priority over other needs and if the diet does nor furnish
sufficient calories from carbohydrates and fats, the [proteins of the diet as well as tissue proteins are
catabolized for energy.
Proteins provided a higher satiety value as compared to carbohydrates as they take longer time to
get digested in the stomach.

16. PROTEIN
PROTEINS ARE ESSENTIAL FOR
 Repair, maintenance and growth of tissues
 Formations of essential body compounds like:
 Hormones
 Enzymes
 Haemoglobin
 Blood Clotting
 Certain Vitamins
 Rhodopsin

17. PROTEIN
 Regulation of water balance in the body
 Maintenance of body neutrality
 Stimulation of antibody formation
 Providing energy
 Higher satiety value than carbohydrates.

18. PROTEIN
EXCESSIVE INTAKE OF PROTEIN
If the diet contains proteins far beyond the recommended allowance, its costs tends to be high and such diets allow excess amino acids to be
used for energy.
Atherosclerosis and heart disease are more prevalent in countries with a high consumption of animal protein. If some of the animal protein is
replaced with vegetable protein, the plasma cholesterol levels are reduced.
The high protein diets produce large amounts of nitrogenous waste like urea, which can be excreted by the normal kidney, provided the
fluid intake is also increased.

19. PROTEIN
PROTEIN DEFICIENCY
A sub optional intake of protein over a relatively long time, leads to depletion of the tissues. The speed with which the deficiency developes
depends upon the quality and quantity of the protein intake, the calorie intake, the age of the individual and other nutritional factors associated
with protein metabolism. The various signs and symptoms in case of adults, gradual loss of body weight, weakness, lack of appetite, great
susceptibility to infection, delay wound healing and convalescence, lack of vigour and oedema. In case of children between one to four years of
age, Kwashiorkor is a major health problem in developing countries. It is mainly because these children are fed with carbohydrate rich diets
with very little protein, which is basically from plant sources.

20. PROTEIN