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What is Protein

What is Protein - Structure, Functions, Types, Sources & Forms of Protein Supplements

Protein is an important part of your everyday meal. Our routine diet can provide us with enough protein to prevent deficiency. But, sometimes, extra protein must be incorporated into your diet for some extra benefits. In the following article, you will find all you need to know about proteins.

What is protein?

Proteins are macromolecules, i.e., required in larger quantities by your bodies, made up of long chains of amino acids. One (1) gram of protein provides 4 calories, but this is not the primary function of the protein. Protein is responsible for the repair, growth, and protection of your tissues, as well as for catalyzing metabolic reactions. The characteristics of protein differ according to the arrangement of amino acids and the structure formed by the polypeptide chain. 

According to the Oxford dictionary, "Proteins are any of a class of nitrogenous organic compounds which have large molecules composed of one or more long chains of amino acids and are an essential part of all living organisms, especially as structural components of body tissues such as muscle, hair, etc, and as enzymes and antibodies."

Amino Acids - Building Block of Protein

Amino acids are organic compounds that contain a carboxyl group (-COOH) which acts as an acidic group, an amino group (-NH2) serving as a basic group, and a neutral organic side chain which is unique to each amino acid. Around twenty amino acids makeup all the proteins in the human body. Out of which, nine are considered essential that are histidine, methionine, leucine, valine, phenylalanine, isoleucine, threonine, tryptophan, and lysine. The sequence and number of amino acids in a peptide chain are responsible for the distinguishable characteristics of each protein.

    Structure Of Protein

    Proteins are complex structures consisting of long chains of amino acids linked with a peptide bond. A peptide bond is a covalent bond that is formed when an amino group of one amino acid is attached to the carboxyl group of adjacent amino acid, and a water molecule is released. The diversity of protein structures determines the functions performed by proteins, i.e., binding, catalysis, regulation, transport, etc.

    Proteins are sub-divided into 4 levels based on their structures, i.e. Primary, Secondary, Tertiary & Quaternary structure

    Primary Structure Of Protein

    The primary structure of a protein is the sequence in which amino acids are linked together in a polypeptide chain. This sequence describes the distinguishing characteristics of the protein. Alteration in the primary structure of the protein may occur due to genetic mutations and thus affect the overall efficacy of the protein.

    Secondary Structure Of Protein

    The secondary structure of a protein is formed when the polypeptide chain folds due to hydrogen bonds formed between carboxyl and amine groups of peptide linkages. This may result in either of the two structures, i.e., α-helix and β-pleated sheet.

    An α-helix is formed when a peptide chain forms all possible hydrogen bonds creating a spiral.

    β-sheet is a pleated structure formed when peptide chains are straightened out and held together parallel by intermolecular hydrogen bond.

    Tertiary Structure Of Protein

    The tertiary structure of the protein is a biologically active, characteristic three-dimensional structure formed by the folding and coiling of the secondary structure due to different kinds of intermolecular forces. It gives rise to the shape of the protein that is either fibrous or globular.

    Quaternary Structure Of Protein

    Some proteins are oligomers or polymers of different polypeptide chains. These chains, held together in a spatial arrangement within a protein, form a quaternary structure of proteins.

      Types of Protein

      Proteins can be divided into two types based on molecular shape.

      Fibrous Proteins

      Fibrous Proteins are formed when polypeptide chains are organized in parallel along a single axis and are joined together by hydrogen bonds and disulfide bonds, creating a fiber-like structure. These proteins are stronger and are generally insoluble in water. Fibrous proteins usually play structural roles.

      For example - Collagen (present in bones, skin, muscles, etc.), myosin (present in muscles), keratin (present in hair), etc. 

      Globular Proteins

      Globular Proteins are formed when the chains of polypeptides twist and wind around to give a three-dimensional spherical shape. These proteins are most abundant in nature and have high solubility in water.

      For Example – Insulin, hemoglobin, and albumin

      Functions of protein

      Growth and maintenance

      Protein is a major constituent of various tissues and muscles and is responsible for growth and maintenance. Protein needs to increase in case of injury or surgery or during pregnancy and lactation.

      Aids in biological processes

      Proteins as hormones and enzymes are responsible for carrying out different metabolic reactions and transmitting nerve signals.

      Transportation of nutrients

      There are various transport proteins in your blood, which are responsible for carrying different nutrients and gasses in your body.

      Provide structure

      Protein, like collagen in bones and skin, is responsible for providing strength and structure to the body.

      Immunity

      Proteins help in the production of antibodies and immunoglobulins to fight infections.

      Acts as a buffer

      The protein acts as a buffer and maintains the pH of the blood and other body fluids.

      Fluid balance

      Proteins such as Globulin and Albumin help to maintain your body's fluid equilibrium by drawing and holding onto water.

      Provides energy

      One gram of protein provides 4 calories. However, it is not the primary function of the protein. Protein is responsible for energy production during starvation.

      Why is protein important?

      Protein is an essential nutrient as it is vital in almost all body functions.

      • It is crucial for tissue repair and muscle growth.
      • It, being a part of muscles and joints, plays a vital role in mobility.
      • Protein provides energy to the body while fasting.
      • It helps in fighting infections.
      • Enzymes are proteins in nature that are responsible for various metabolic reactions.
      • Clotting factors, e.g., Fibrinogen in your blood, are also protein in nature.
      • Collagen protein is responsible for skin elasticity.
      • Protein is also essential for healthy hair and nails.
      • Protein present in blood vessels is responsible for the elasticity and thus maintains normal blood pressure.
      • Protein in muscles retains fluid and allows them to contract and relax.

      Sources of Protein

      Dietary sources of protein

      Protein is a macronutrient found in various animal and plant-based food. Eggs, milk, meat, and their products come under the umbrella of animal-based protein-rich foods. Whereas lentils, beans, nuts, and soy are plant-based protein sources.

      Animal-based protein-rich foods

      • Seafood: fish, pawns, crab, oyster, etc.
      • Poultry: eggs and chicken
      • Red meat: beef, veal, mutton
      • Dairy products: milk, yogurt, cheese
      • Organ meat: liver

      Plant-based protein-rich foods

      • Beans
      • Chickpeas
      • Lentils
      • Nuts
      • Soy
      • Grains and cereals

      Quality of protein

      Protein from foods may or may not contain all the essential amino acids. The proteins that provide a well-balanced proportion of all the essential amino acids and are easily utilized are called good-quality proteins. Animal proteins are better quality proteins as compared to plant-based proteins.

      A complete protein is a protein that provides all of the essential amino acids necessary to be taken via an outside source.

      Protein shakes, protein powder, and protein supplement

      Protein is essential for achieving all of your fitness goals and is becoming more and more readily available in the form of protein supplements. They are more frequently consumed by athletes to boost performance, build muscle mass, and enhance post-exercise recovery. Protein supplements are frequently offered in powder as well as ready-to-drink liquids.

      Forms of protein supplements

      Protein concentrates

      Protein concentrates contain 60-80% protein, and the rest are carbs and fats. These are derived from whole food using heat, enzymes, or acids.

      Protein isolates

      These undergo further heat or enzyme activity to remove carbs and fats and contain 90-95 % protein.

      Protein hydrolysates

      A more absorbable form of protein is prepared by heating enough proteins to break the bonds between amino acids.

      Animal-based protein supplements

      Protein supplements derived from animal sources are complete proteins and therefore are more effective. These include whey protein, casein protein, egg protein, and some forms of collagen protein.

      Whey protein

      Whey protein is a milk byproduct. It can be found in the liquid that remains after creating curd or yogurt. It is absorbed swiftly and is a rich source of branched-chain amino acids (BCAAs). Leucine, a branched-chain amino acid, increases muscle growth and recuperation after resistance and endurance training. As a result, athletes tend to use it more frequently. Besides that, it is also observed to increase feelings of satiety.

      Casein protein

      Casein is also a component of milk, but it digests and absorbs considerably more slowly than whey protein. When casein interacts with stomach acid, a gel is created that slows down the emptying of the stomach and delays the absorption of amino acids into the bloodstream. Your muscles are exposed to amino acids more gradually and steadily as a result, which slows down the rate of protein breakdown in your muscles.

      Egg protein

      Among all whole foods, eggs are known to provide the best quality and more readily digestible proteins. Besides that, egg as an entire food also suppresses hunger and enhances the feeling of fullness. However, the supplement derived from eggs is based on egg whites only. Therefore, you may feel less full. Egg protein is the second largest source of leucine after whey protein. Leucine is the BCAA that plays the largest role in muscle health.

      Plant-based protein supplements

      Protein powders derived from plant sources are richer in fiber and are a suitable option for vegans and vegetarians. The plant-based proteins are almost close to complete protein and can provide the same benefits as animal-based protein supplements.

      Pea protein

      Pea Protein is sourced from yellow split peas, which are high in fiber and contain all but one of the essential amino acids. Its BCAA content is also exceptionally high and is anticipated to enhance body composition and encourage fullness just as effectively as protein powders derived from animals.

      Rice protein

      Lately, brown rice Protein powders are becoming more common. Although rice protein includes all necessary amino acids, it lacks enough lysine to be regarded as a complete protein. However, whey protein is considered superior to them for muscle growth.

      Why should I take protein shakes?

      The purpose of supplementing your diet with extra protein is to enhance your total protein intake. You may need these supplements to gain muscle mass, shed some excess fat, recover muscle after exercise, and improve overall fitness.

      Gain muscle mass

      Resistance training followed by protein supplements promotes muscle growth and overall performance.

      To shed some extra fat

      A protein-rich diet can enhance the feeling of satiety by promoting the release of hunger-reducing hormones. Besides that, protein boosts your metabolism, which also aids in weight loss.

      For recovery of muscle after exercise

      Protein shakes provide the right balance of amino acids, easily digested and absorbed in the human body, thus significantly promoting muscle recovery.

      To improve overall fitness

      Protein supplements are helpful in losing extra fat and promoting healthy muscle gain, therefore improving overall fitness.

      Why should I stop taking protein shakes?

      You should immediately stop taking your protein supplement or protein shake if

      • Do you feel any adverse symptoms or an allergic reaction? The symptoms include nausea, bloating, cramps, fatigue, constipation, and a feeling of illness.
      • If you have any food allergy, you should strictly refrain from that particular ingredient or protein. For instance, if you have lactose intolerance, dairy-based protein is not to be your choice. Similarly, gluten and soy protein ought to trigger allergic responses in some people.
      • If your protein requirements are already being met through diet.

      Protein losses

      Protein from the body is lost under stressful conditions. Some of the reasons for protein losses include injury, burns, medical procedures like surgery, dialysis, etc., proteinuria (excessive protein in urine), sweating due to high physical activity, and fasting/starvation.

      How much protein do I need?

      There are a few variables that affect age, muscle mass, general health, and activity level that affect how much protein you require. Protein intake recommendations range from 0.8 to 1 gram per kilogram of body weight. The demand may rise or fall depending on the particular circumstance. You can determine your protein needs more precisely with the advice of a certified dietitian or nutritionist by taking all the relevant factors into account.

      Who needs extra protein?

      Young children and infants, pregnant and lactating mothers, the elderly suffering from sarcopenia, and bodybuilders need to add extra protein to their diets to promote muscle growth and prevent muscle depletion. Furthermore, people undergoing surgery, burn, trauma, or injury also have higher protein needs to accelerate healing.

      Side effects of proteins

      Overconsumption of any nutrient can bring along serious health issues. The same happens with overdosing on protein. Some of the health concerns are as listed below

      • Excess protein is stored as fats and can cause unhealthy weight gain
      • You may experience bad breath because your body goes into ketosis, which results in the release of chemicals that may emit a foul odor.
      • Constipation or diarrhea may also occur due to a lack of fiber in the diet.
      • This can leave you dehydrated as water and fluids are removed on the removal of excess nitrogen from the body.

      Summary

      Protein plays a significant role in making muscles, tendons, organs, skin, enzymes, hormones, antibodies, and other biomolecules in our body. This way, they are vital nutrients to perform almost every function, from strength, protection, and structure to metabolism and neurotransmission.

      Most of the time, the protein needs are met through the diet only, but sometimes supplements may be introduced to enhance the protein intake. The extra protein or protein-rich diet helps in weight loss and muscle growth and repair. For that purpose, protein supplements in the form of powders and shakes are readily available in the market.

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