Proteins

Proteins make enzymes that power many chemical reactions and haemoglobin. More than 10,000 different proteins form the human body. Twenty amino acids link together in different combinations to make a protein. Our bodies utilise them to form more proteins, such as muscles, bone, hair, etc. They also make other compounds like enzymes and hormones. Proteins are naturally occurring, complex nutrients that consist of amino acid residues joined by peptide bonds. 

Structure of protein

Max Perutz (1953) proved for the first time that protein has a specific arrangement of amino acids along its chain.

Sanger (1958) presented the primary structure of insulin that contains 51 amino acids and is made up of two polypeptide chains held together by disulphide bonds.

secondary structure

The polypeptide chain can twist or fold onto itself to form various types of structures.

a-helix: It is the simplest form of twist and polypeptide forms a helix. Helices are right handed as well as left-handed. In a-helix there are 3.6 amino acids per turn of the helix, the distance of single turn of helix is 5.4A° and each amino acid residue represents an advance of 1.5 A° long axis of the helix. Amino acids are stabilised by hydrogen bonds between every 1st and 4th amino acids. Amino acid must be either all D- or all L-amino acid.

Examples: Keratinis, hair, wool, horns and nails etc. Hair contains 3 a-helices coiled together; wool has 7 a-helices coiled together, a-helices change into b-conformation by treating with moist heat due to breakage of H-bonds.

Beta-pleated sheet: Beta-pleated sheet hydrogen bonds form between the peptide bonds either in different polypeptide chains or in different sections of the same polypeptide chain. This gives a zigzag pleated sheet like appearance. Adjacent polypeptide chains in b-pleated sheets may be either parallel or antiparallel depending upon the same or anti-direction. b-pleated sheets are always slightly curved. e.g., feather, fibroin.

 tertiary structure

It is the three dimensional structure of protein.It is the most stable structure of protein.High temperature denatures this structure

quaternary structure

This level of structure refers to the spatial arrangement of the polypeptide subunits and the nature of the interaction between them. These interactions may be covalent links e.g., disulphide bonds or non-covalent interactions e.g., electrostatic forces, hydrogen bonding, hydrophobic interactions

Nutritional value of proteins

The quantity of essential amino acids the protein contains defines its nutritional value. The quantity varies between the foods.

• Non-vegetarian products like chicken, beef, fish, pork, and dairy contain the most vital amino acids and are ideal for high-quality proteins

• Products like soy, quinoa, and amaranth have all the necessary amino acids

• Plants like beans, lentils, nuts, and whole grains usually lack essential amino acids. Therefore, they are considered ‘incomplete’ proteins

People who prefer taking a vegan diet should choose a variety of proteins from various plant foods daily. This should be done to make sure that they get an adequate quantity of amino acids required for the functioning of the body. 

For instance, a meal containing cereals and pulses, such as baked beans on toast, can serve them all the essential amino acids found in a good meat dish.

Proteins for daily consumption

Around 10-35% of daily calories are consumed in protein. The National Academy of Medicine recommends that adults follow a diet of at least 0.8 gm of protein for every kilogram of body weight every day. This means over 7 gm for every 9 kg of body weight. For instance, a person weighing 63 kg should consume 50 gm of protein each day, and a person weighing 90 kg should consume 70 gm of protein each day.

Sources of protein

Seafood: Seafood is an excellent source of protein because it has a low-fat content. Fish such as salmon might be higher in fat, but it carries omega-3 fatty acids suitable for heart health.

White-meat poultry: Dark meats have higher fat content than lighter ones. It is better to remove their skin full of saturated fat. White meats are full of lean protein and, hence, are better.

Milk, cheese, and yoghurt: Dairy foods are brilliant protein sources. Still, they also contain vital minerals like calcium and vitamin D. You may have skim or low-fat dairy to keep bones, teeth, and gums strong to prevent osteoporosis. 

Eggs: Eggs are rich in protein. Adults can have an egg or two daily for a good-protein diet.

Beans: One major perk of consuming plant protein is that they are rich in protein and have a beneficial amount of fibre loaded in them. This fibre helps to keep the stomach full for hours. One-and-a-half cups of beans contain 29 gm of protein.

Soy: Just 50 gm of soy protein every day can help lower cholesterol by about 3%. It can be an excellent alternative to animal-based protein.

Lean beef: It contains 2 gm more saturated fat than a skinless chicken breast. Moreover, it contains zinc, iron, and vitamin B12, making it an excellent addition to your diet.

Almonds: Along with good protein content, they are rich in fibre, vitamin E, manganese, and magnesium.

Oats: Oats are rich in protein and provide healthy fibre, magnesium, manganese, vitamin B1, and other nutrients.

Tuna: It can be eaten hot as a baked dish or cold in a salad. One tuna may contain 27 gm of protein. It is low in fat and contains omega-three fats suitable for our bodies.

Protein and exercise

To maintain the body’s protein balance, it is often recommended to have high-quality protein like a glass of milk or yoghurt with a carbohydrate meal after a session of exercise. Studies reveal it is perfect for the body, even if consumed after a low aerobic exercise. However, people who wish to put on muscle mass are not advised to have extra protein. Including more protein in the diet does a little to increase muscle mass. It is just the exercise, the stimulation of the muscle tissue, that leads to muscle growth. Dietary protein has a minor role in that. This can be seen by the fact that weight trainers who do not consume extra protein gain muscles at the same rate as weight trainers who supplement their diets with protein.

Conclusion

Getting the right amount of protein as per body requirements at adequate intervals helps gain muscle mass and is suitable for overall health. Protein is necessary, but a counterbalance should be established to cut down the supposed detrimental effects of protein. It can be done by taking a varied diet rich in fruits and vegetables. You are required to build a solid nutritional body around various foods.