Proteins: Their Functions, Benefits, Sources Types & Roles

What are Proteins?

There are so many vital nutrients that we need to stay healthy, they give us energy and are responsible for the proper functioning of the organs. While micronutrients like vitamins and minerals help in the growth and keep diseases away, they are joined by macronutrients like fats, carbohydrates and proteins that provide energy and make up and repair cells in the body. Since these macronutrients are needed in large quantities by the body it is for that reason they are called “macro” nutrients. 

Among these macronutrients, proteins are essential for developing muscle mass, that’s why it is a vital component in the daily diet of fitness enthusiast and bodybuilders. Animal products are the most abundant sources of protein while other sources are nuts and pulses, hemp and whey. Each gram of protein contains four energy units or calories and they make up to 15% of a person’s body weight. Apart from building muscle mass, proteins boost the immune system, enhance metabolism and helps a person stay full for a long time. 

Proteins are present in every cell of our body and contribute to the building and repairing of the cells and tissues. It is the fundamental ingredient in the making of skin, muscle, nails, hair, bones and organs. Proteins are a mix of 20 amino acids and different orders of the composition of these amino acids make up different types of proteins. Proteins tend to work wonders in crucial situations and have proven to be a vital source of energy and keeping a person alive in critical situations like insufficient calorie consumption, fasting and extreme workouts. 

Types of Proteins 

There are various protein types, lets discuss each one by one and know their composition and what they do for our bodies.

1. Digestive Enzymes

Digestive enzymes are responsible for enabling biochemical changes in the body. They catabolize various nutrients during the digestion process. For example, pepsin contributes to breaking down proteins in food in the stomach. It is a complex protein that acts as a facilitator during biochemical reactions in the body. Another example is saliva which consists of an enzyme called amylase that breaks down starch into sugar. 

2. Transport

Transport proteins are responsible for transporting molecules around the body. These molecules are transported in the blood or lymph throughout the body. Haemoglobin is a type of transport protein that is used to transport oxygen throughout the blood. There are different kinds of transport proteins like carrier proteins, membrane transport proteins, and vesicular transport proteins and each of them is responsible for carrying various vital components throughout the body. 

3. Structural

I don’t want to sound literal but I guess it’s the only way, structural proteins are responsible for building structures in our body to provide mechanical support to our body. Structural proteins like collagen, fibronectin and laminin act as attachment factors in cell culture applications. They are generally fibrous and are most abundant as compared to other proteins. 

4. Hormones

Hormones are responsible for coordinating the smooth functioning of various organs in the body. They are produced by the chains of amino acids. They are organic particles that help in the growth, reproduction and development of the human body. For example, insulin regulates blood sugar concentration by normalizing the uptake of glucose into cells, antidiuretic hormones help decrease blood pressure and gastrin encourages the emission of gastric acid and aid in gastric motility. 

5. Defence

As the name suggests, defence proteins protect the body from foreign contaminants and infections. They are produced by the immune system to fight pathogens and protect the body from harmful diseases. Defence proteins like antibodies are made up of a three-dimensional structure which enables them to identify specific foreign contaminants and bind to them. Binding helps them to neutralize these pathogens and remove them from the body. 

6. Contractile

Contractile protein enables the movement of muscles in the body. The cytoplasm of cells in itself is made up of contractile protein. They are responsible for the descending of contractile fibres of the cell’s cytoskeleton, skeletal muscles and cardiac muscles. Myosin and actin are thick and thin filaments respectively are contractile proteins that makeup myofilaments which makeup muscle fibres of the skeletal muscles and are responsible for the contraction and relaxation of muscles.

7. Storage

Storage proteins are responsible for nurturing and protecting the embryo and the seedlings due to the initial period of development. They act as reserves of metal ions and amino acids which is later used in the development of the embryo in both plants and animals. Ovalbumin and casein are two of the storage proteins present in animals whereas, prolamin gliadin is a storage protein found particularly in wheat. 

Role & Function of Proteins

Proteins are needed for the growth and repair of the body and to make cells, especially protoplasm. Their main function is to provide the body with abundant energy to survive when all the carbohydrates and fat is consumed and nothing is left. Proteins are broken down by the body when it faces starvation. It is essential for blood clotting, fluid balance, enzymes, hormones, normal vision, and immune system. It must be consumed abundantly during pregnancy and the formative years of children. Here are some of the important functions of proteins which must be read carefully by everyone, especially by those who believe that protein are only essential for gaining muscle and building a fitter body:

1. Source of Energy

Proteins are a vital source of energy but it not used by the body for their daily use. The body derives its daily energy quota from carbohydrates and fats that produce the same amount of energy as proteins. Bodies release energy from proteins only when the other two sources have exhausted their limit and have nothing left which happens during starvation, fasting and intense workout sessions. In such conditions, the body breaks down its skeletal muscle to let amino acids supply energy. 

2. Storage of Nutrients

Transport proteins carry vitamin, minerals, oxygen, cholesterol and other nutrients in and out of the cells and also within the cells. For example, haemoglobin carries oxygen from lungs to tissues and glucose transporters carry, of course, glucose to the cells. One thing to remember here is that one transport protein doesn’t carry all substances but only carry the substance that it is meant to carry like haemoglobin will only carry oxygen and not cholesterol. Also, they store nutrients, only a needed amount is released and the rest is stored for later, like ferritin stores iron.

3. Growth 

The body needs proteins for its growth, repair and its sustenance. The release of proteins depends on the need of the body. Normally the protein need depends on your health and activity level but at times the need increases from usual. For example, usually, the body breaks down the same amount of protein that it breaks down during building and repairing tissues, but during illness, pregnancy, injury, or breastfeeding is when the body needs more proteins to heal, so the breakdown of protein is more than usual. 

4. Biochemical Reactions 

The type of protein responsible for biochemical changes within and outside the cells are the enzymes. Enzymes are made up in such a way that allows them to combine with molecules called substrates that are present inside the cell. They catalyse many reactions that are suitable for metabolism. Outside the cell, digestive enzymes such as lactase and sucrose contribute to the digestion of sugar in the body. Enzymes also need vitamins and minerals for creating reactions that help in producing energy, blood clotting, contraction of muscle and digestion.

5. Strengthens Immunity

If you have survived 2020 then I’m sure you must be well-versed with the term antibodies and also with what they do. If not, then let me tell you that antibodies or immunoglobulins are proteins present in your blood that protect you from bacteria and viruses. When we are attacked by bacteria and viruses, our body automatically generates antibodies that tag these substances and eliminate them. If not for them, our bodies are at risk of infections and illnesses caused by harmful pathogens like them. The best part is that once our bodies produce antibodies against any virus, it never forgets how to make them and respond accordingly in the future. Having antibodies in our body is a sign that our immune system is strong. 

6. Balancing Fluids

It is important to balance fluid intake properly and regulate it throughout the body effectively. Albumin and globulin are two proteins in the blood that are responsible for the conservation of body fluids by attracting and retaining water. The absence or scarcity of proteins in the body subsequently decreases the levels of albumin and globulin. Due to this, there is nothing to keep blood inside the blood vessels which results in the fluids to build up into the spaces between the cells. This build-up results in a condition called oedema in the stomach region which is a form of kwashiorkor, a severe malnutrition condition occurring when enough calories are taken but not enough protein is taken into the diet. 

7. Messenger

Proteins act as chemical messengers that act as links of communications between cells, organs and tissues. They are generated and secreted by endocrine tissues and then sent back into the blood to their directed organs where they bind to protein receptors on the surface of the cells. For example, protein and peptides are made from amino acids and are up to several hundred. Steroids such as testosterone, oestrogen and sex hormones are produced by fat cholesterol. Amines are made from single amino acids tryptophan or tyrosine which are responsible for making hormones related to metabolism and sleep. 

8. Offers Structure

Proteins like keratin, collagen and elastin are fibrous and give toughness and rigour to the cells and tissues. These proteins are responsible for the formation of a connective framework of all the structures that are in the human body. Keratin provides structure to the hair, skin and nails. Elastin is an incredibly elastic protein and due to its elasticity, many tissues like the uterus, lungs and arteries can return to their original shape after stretching or contracting. Lastly, collagen is the amplest protein in the body which is present in the ligaments, skin, tendons and bones. 

9. Maintains pH Levels

One of the most important function that protein has is the regulation of the pH level of various acids and bases in our blood and additional bodily fluids. The steadiness of acids and bases is measured by using a pH scale ranging from 0 – 14 with 0 representing most acidic, 7 representing neutral and 14 representing most alkaline. It is important to balance acids and bases, otherwise, it can prove fatal. Our body regulates pH levels through various buffering systems. Proteins like haemoglobin help maintain pH levels by binding small quantities of acids. Other buffer systems are phosphate and bicarbonate.

Dosage of Proteins 

The amount of protein needed by a person depends upon their age, their gender and their calorie intake. For example, if a person is on a 2000 calorie per day diet then he/she should consume 50 grams of protein. Other factors that determine the protein intake include the amount of amino acid in a food item, the digestibility of each amino acid, activity level, weight, and height of the person. 

Children aged from 1 – 3 years must be given up to 13g of proteins, children aged from 4 – 8 years must have 19g and children aged 9 – 13 years must have 34g of proteins. Teen males should have up to 52g and teen females should have up to 46g of proteins. Adult males must consume up to 56g and adult females must have up to 46g of protein in their diet.

Having 1 gram of protein per kilogram of your body weight is also an adequate method of managing your protein intake, but it can vary among people who want to gain a muscular physique in which case having 2 – 3 grams per kilogram is a more suitable option. 

Also, after the age of 40 the body starts to drop 3 – 5% of its muscle mass after every 10 years, this condition is commonly known as sarcopenia, which is the leading cause of fractures among the elderly. An increase in protein intake and regular exercise in the advanced age will preserve the muscle mass of the body and prevent conditions like sarcopenia to creep up. 

Sources of Proteins 

Proteins are made up of 20 amino acids which are arginine, alanine, asparagine, aspartic acid, cysteine, glutamic acid, glycine, glutamine, isoleucine, histidine, leucine, methionine, lysine, proline, phenylalanine, serine, tryptophan, tyrosine, threonine, and valine. 

Among those 20 amino acids, 9 can’t be created by the body hence they must be consumed through a proper diet. Also, there are complete and incomplete proteins, those protein that have all the essential amino acids in them are called complete proteins. If complete proteins are not available then different incomplete proteins can be consumed together to get all essential proteins. 

Both plants and animal products are rich sources of protein like seeds, nuts, eggs, meat, poultry, dairy products, soy, seafood, pulses, brown rice, chickpeas, and beef. Animal products are complete proteins usually and most plants are incomplete proteins. For vegans or lactose intolerant who can’t eat meat and dairy products can have proteins through supplementing proteins with an additional intake of amino acids. 

Protein Deficiency 

Protein deficiency is a serious concern in developing countries and has resulted in life-threatening diseases like kwashiorkor, marasmus and malnutrition. Apart from poor dietary habits protein deficiency can be caused if a person has an eating disorder, anorexia, malignant cancerous tumours, genetic disorders, irritable bowel syndrome, and gastric bypass surgery.

Protein deficiency, if not treated in time, can lead to having a weak muscle tone, oedema or swelling caused due by the retention of fluids in the body, thin or brittle hair, skin lesions, losing muscle mass, insufficient growth among children and hormonal imbalance. 

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