Proteins | Types, Functions, Examples & Importance

The word 'Protein' is derived from a Greek word 'Protas' which means 'primary importance'. It was discovered by Jons Jakob Berzelius in 1838. It is one of the basic building blocks of the human body and present in every single cell. It is essential for maintenance of the body tissues, including development and repair in children, teens, and the pregnant woman, proper immune system function, digestion, hair, and nail growth and also involved in other body functions.

What Are Proteins?

Proteins are micronutrients which are made up of smaller units called amino acids. They are also called the primary foodstuff. Proteins contain carbon, hydrogen, nitrogen, oxygen, and less commonly sulfur, phosphorus, iodine, and iron. They can be found in both animal and plant foods. When intake proteins from the foods, they are broken down into smaller parts called amino acids during digestion in our bodies. 

What are amino acids?

Amino acids are the organic nutrients that are found in the food as well as in the human body either in the form of building blocks of proteins or as free amino acids. All the amino acids have a basic skeleton which is made up of a carbon linked to an amino group(NH2), a carbonyl group(COOH), a side chain containing carbon, oxygen or hydrogen atom. 
The bond which connects the amino group of one amino acid to the carbonyl group of another amino group is called a peptide bond.  This bond is also called the covalent bond. When a number of amino acids are linked together by the peptide bonds, a polypeptide chain is formed. Large amounts of amino acids need to maintain good health in the human body.
Amino acids are mainly divided into three groups. They are

1. Essential amino acids: Proteins naturally found in the form of 21 amino acids. Out of 21 amino acids, 9 for adult and 10 for children are important for maintaining the human health. These amino acids are called essential amino acid. The important essential amino acids are Histidine, Isoleucine, Leucine, Threonine etc. They cannot be produced by the human body. So, you have to get essential amino acids from foods. They also provide a source of energy like proteins which provides about 4 calories per gram.
2. Non-essential amino acids: Non-essential amino acids are formed due to the normal breakdown of proteins in the body. The examples of important non-essential amino acids are Alanine, Asparagine, Aspartic acid, Serine etc. 
3. Conditional amino acids: Conditional amino acids are essential at the time of illness and stress. Some examples of conditional amino acids are Arginine, Glycine, Tyrosine.

Types of Proteins

Generally, Proteins fall into one of three types. They are
1. Globular Proteins: They acts as enzymes, chemical signaling compounds, transporters of other compounds, and antibodies. Hemoglobin is the example of globular proteins. Myoglobin is another example of a globular protein. It is used to store the oxygen in muscle tissue.  Albumin is another example of a globular protein. It is the amplest protein in human blood plasma. Its biological functions include transporting hormones, fatty acids, and acts as a buffer and maintaining osmotic pressure.

2. Fibrous Proteins: Fibrous proteins play important roles in providing structural rigidity and in contractile movement. An example of a fibrous protein is collagen. It is a strong, fibrous protein made up of mostly glycine and proline amino acids. Collagen is the most abundant protein in the body and makes up 30 percent of bone tissue and comprises large amounts of tendons, ligaments, cartilage, skin, and muscles.  Its function is to provide structural rigidity and stiffness. It is found in skin, ligaments, tendons, and other parts of the body. It makes the bone strong and flexible. Keratins are other examples of fibrous proteins. Hair, skin, and nails are made of keratins.

3. Membrane Proteins:  Membrane proteins function as enzymes, cell recognition, receive chemical signals between the interior and exterior of cells and transports the chemical signals in and out of cells. An example of membrane proteins is Aquaporins. Aquaporins acts as transporter proteins. They facilitate the transport of water molecules in and out of cells.

Protein's Functions in the body

Proteins participate in different types of function in the body. They are as follows.
1. Enzymes: Enzymes are proteins that conduct specific chemical reactions in the body. An enzyme’s function is to provide a site for substances to chemically react and form a product and lower the amount of energy and time it takes for that chemical reaction to happen. This process is called catalysis. In every single second, On an average, more than one hundred chemical reactions occur in cells and most of them require enzymes. The liver alone contains over one thousand enzyme systems.

2. Hormones: Proteins are responsible for hormone synthesis. Hormones are the chemical messages which are produced by the endocrine glands. When an endocrine gland is stimulated, it releases a hormone and then it is transported in the blood to its target cell, where it communicates a message to initiate a specific reaction or cellular process. For example, after eating a food, your blood glucose levels increase. In response to the increased blood glucose, the pancreas releases the hormone called insulin. Insulin tells the cells of the body that glucose is available and take it from the blood and store it for making energy or building macromolecules. Hormones play a very important role to turn enzymes on and off.

3. Transport: Albumin and hemoglobin play an important role in molecular transport. Albumin
chemically binds to hormones, fatty acids, some vitamins, essential minerals, and transports them throughout the circulatory system. Each red blood cell contains millions of hemoglobin molecules that bind oxygen in the lungs and transport it to all the tissues in the body.

4. Energy: Proteins provide a good source of energy. It contains 4.2k calories of energy per gram protein. If a person's diet contains more proteins than the body needs, the body will use it for energy. If you do not take sufficient amount of carbohydrates and fats, your body will use more amino acids to make energy, which compromises the synthesis of new proteins and destroy the muscle proteins but if you intake extra proteins than the body needs, the extra amino acids will be broken down and transformed into fats.

5. Antibodies: Antibodies are the glycoproteins that help to prevent from infection, diseases, and illness. These proteins help to destroy harmful bacteria, and viruses. The antibodies are secreted by the white blood cells that search the entire circulatory system for harmful bacteria and viruses to surround and destroy them. They also act as a trigger for other factors in the immune system to seek and destroy unwanted intruders.

6. Blood Clotting: Fibrinogen is a glycoprotein that involved in the healing of wounds. For example, when you get an injury from a needle of sewing, your flesh is turned red and become inflamed. Within a few seconds, bleeding would stop. The healing process starts with proteins such as bradykinin, which enlarge blood vessels at the site of injury. An additional protein called fibrin helps to form a clot to stop the bleeding.

7. Maintaining pH balance: Protein is also essential in maintaining proper pH balance in the blood. Blood pH is maintained between 7.35 and 7.45, which is slightly basic. If a slight change in blood pH occurs then it will affect your body functions.

How many grams of protein do you need per day?

Since hair, skin, eyes, muscles, and organs are all made up of proteins. So a high-quality protein diet is essential for the human healthy body. The recommended daily allowance of proteins for a woman is 46 grams/day whereas for men is 56 grams per day.
The protein requirement for children are:
Age 0 to 6 months: 9 grams per day.
Age 7 to 12 months: 11 grams per day.
Age 1 to 3 years: 13 grams per day.
Age 4 to 8 years: 19 grams per day.
Age 9 or older: 36 grams per day.

Protein Sources

High protein foods: Meat, Fish, Eggs, Beans, Bread, Nuts and Seeds, Milk, Soybeans etc.
Low protein foods: Legumes, Green peas, Vegetables, Rice, Wheat, Peanut butter etc.
Proteins definition, types, function, sources, and importance of proteins.
Proteins amounts

What is Protein deficiency?

When your intake of protein from food does not fulfill the requirement of sufficient proteins in your body, it is called protein deficiency. An estimated one billion people in the world-wide are suffering from inadequate protein intake. In India, 9 out of 10 Indian people are protein deficient. If we are talking about Urban Indian, Around 73% diet is protein deficient whereas 84% of the vegetarian diets are low on protein as against as non-vegetarian diets. 
The most severe form of protein deficiency is Kwashiorkor and Marasmus which mostly occurs in children in the developing countries. Protein deficiency can affect all the function of the body. There are 12 sign and symptoms of protein deficiency. They are listed below:
1. Low energy levels.
2. Trouble building muscles.
3. Trouble learning.
4. Poor concentration.
5. Muscle, bone, and joint pain.
6. Hair fall, Baldness.
7. Low immunity
8. Losing weight
9. Irregular Periods.
10. Sluggish Metabolism
11. High Cholesterol
12. Slow wound healing
If you are experiencing any of these problems then It is the time to check your diets. 

How are proteins important for maintaining our body healthy?

1. Healthy hair: The main problem of hair fall is also a protein deficiency. When there is a lack of protein in our daily diets, our body starts saving the proteins using in the hair growth and our hair does not get adequate proteins for growth due to which so many problems are started such as hair loss, hair thinning, hair dry, and hair whitening. So if you want to prevent your hair fall, you must take enough proteins in your daily diets. 

2. Brain Power: The protein intake in our diet also affects the performance of our brain because the protein provides essential signals to our brain's Nero transmitter which helps it to function better. A neurotransmitter is a basically biochemical messenger which transmit the signals to the brain cells. Proteins also improve your concentration power and memory.

3. Muscles building: If your muscles are not able to build or you have issues of the muscle pain and weakness, it means that there is a shortage of protein in your diet. Protein is essential for building, repairing, and maintaining muscles, ligaments, and body tissues. Protein is essential for growth and replacement of cells. Thus, proteins are essential for body growth and functioning. 

4. Immunity: Due to the lack of proteins, the body's immune system is also affected, causing the risk of diseases and infections because the immune cell of our body is made up of proteins and also repair from proteins. If you are getting sick frequently or you have a frequent cough and cold, allergies and infections, then this may be due to lack of proteins. Therefore you should take adequate proteins in your daily diet and keep healthy and strong.

5. Metabolism: Proteins regulate metabolism. They make 12-15% of diet calories. Proteins provide the base for manufacturing enzymes, hormones, antibodies, etc.

6. Risk of Bone Fractures: Your bones are also affected due to lack of proteins. Insufficient proteins intake may weaken your bone and increases the risk of fractures. Therefore You should take enough proteins to maintain the strength and density of bones.

7. Increased Severity of Infections: Insufficient protein intake can also increase the risk of Infection in your body. Eating too little protein decreases the ability to fight against the infections.

6. Energy: Protein is a source of energy. If you take one gram of protein, it will provide you with 4.2 kilocalories of energy. 

Final words:
I hope that this article will help you to know about the Definition, types, functions, examples, source, and importance of proteins in our daily diet for the healthy and strong body.