Biology – Classes of Food {Protein}



  • What is Protein?
  • Types of Protein
  • Functions of Protein
  • Foods that contain Protein
  • Protein Deficiency
  • General Symptoms of Protein Deficiency


What is Protein?

Proteins are the building blocks of life. Every cell in the human body contains protein. The basic structure of protein is a chain of amino acids. Proteins are very important molecules in our cells. They are involved in virtually all cell functions. Each protein within the body has a specific function. Some proteins are involved in structural support, while others are involved in bodily movement, or in defense against germs.

Proteins can also be defined as  large biomolecules, or macromolecules, consisting of one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, responding to stimuli, and transporting molecules from one location to another. Proteins differ from one another primarily in their sequence of amino acids, which is dictated by the nucleotide sequence of their genes, and which usually results in protein folding into a specific three-dimensional structure that determines its activity.

You need protein in your diet to help your body repair cells and make new ones. Protein is also important for growth and development in children, teens, and pregnant women.

Except for water, protein is the most abundant substance in your body. This protein is manufactured by your body utilizing the dietary protein you consume. It is used in many vital processes and thus needs to be consistently replaced. You can accomplish this by regularly consuming foods that contain protein.

Proteins vary in structure as well as function. They are constructed from a set of 20 amino acids, which are linked to form polypeptide chains. Polypeptide chains that form distinct three-dimensional shapes constitute a protein. Protein is essential to the structure of red blood cells, for the proper functioning of antibodies resisting infection, for the regulation of enzymes and hormones, for growth, and for the repair of body tissue

Proteins are essential nutrients for the human body. They are one of the building blocks of body tissue, and can also serve as a fuel source. Proteins are polymer chains made of amino acids linked together by peptide bonds.

Types of Proteins

Proteins can be classified into three main groups:

Globular proteins: Globular proteins work in the water environment as antibodies and enzymes.

Membrane proteins: Membrane proteins work in the cell membrane and perform functions like membrane transport and signaling.

Fibrous proteins: Fibrous proteins are structured proteins which are found in muscles, bones, ligaments such as keratin which is present in the nails, hair or collagen which is present in the skin.

Functions Of Protein

1. Body/Tissue Maintenance and Repair

Protein is termed the building block of the body. It is called this because protein is vital in the maintenance of body tissue, including development and repair. Hair, skin, eyes, muscles and organs are all made from protein. This is why children need more protein per pound of body weight than adults; they are growing and developing new protein tissue.

2. Production of Enzymes

Enzymes are proteins that increase the rate of chemical reactions in the body. They are proteins that catalyze biochemical reactions, which otherwise would not take place. These enzymes are essential for chemical processes like digestion and cellular metabolism. In fact, most of the necessary chemical reactions in the body would not efficiently proceed without enzymes. For example, one type of enzyme functions as an aid in digesting large protein, carbohydrate and fat molecules into smaller molecules, while another assists the creation of DNA.  Without enzymes, most physiological processes would proceed so slowly (or not at all) that life could not exist.

3. Formation of Antibodies

Antibodies – are specialized proteins involved in defending the body from antigens (foreign invaders). Protein forms antibodies that help prevent infection, illness and disease. These proteins identify and assist in destroying antigens such as bacteria and viruses. They often work in conjunction with the other immune system cells. For example, these antibodies identify and then surround antigens in order to keep them contained until they can be destroyed by white blood cells.

4. Storage and Transportation of Molecules

Protein is a major element in transportation of certain molecules. For example, hemoglobin is a protein that transports oxygen throughout the body. Protein is also sometimes used to store certain molecules. Ferritin is an example of a protein that combines with iron for storage in the liver.

5. Energy Source

Protein is a major source of energy. If you consume more protein than you need for body tissue maintenance and other necessary functions, your body will use it for energy. If it is not needed due to sufficient intake of other energy sources such as carbohydrates, the protein will be used to create fat and becomes part of fat cells.

6. Regulation of Cell Division

Proteins regulate cell division, an important process for replenishing aged or damaged cells. Over time, cells can become damaged from exposure to the sun or other harmful substances in the environment. These cells undergo a natural process of cell death and need to be replaced. This is accomplished by division of healthy cells into two copies, which is regulated by proteins called growth factors. Failure of proteins to properly regulate the division process can cause tumor growth and cancer.

7. Secretion of Hormones

Proteins are involved in the creation of some hormones. These proteins are called Messenger Proteins and they help to coordinate certain bodily activities  Some proteins function as chemical-signaling molecules called hormones. These proteins are secreted by endocrine cells that act to control or regulate specific physiological processes, which include growth, development, metabolism, and reproduction. These substances help control body functions that involve the interaction of several organs. Insulin, a small protein, is an example of a hormone that regulates blood sugar. It involves the interaction of organs such as the pancreas and the liver. Secretin, is another example of a protein hormone. This substance assists in the digestive process by stimulating the pancreas and the intestine to create necessary digestive juices.

8. Contractile Proteins 

They are responsible for movement. Examples include actin and myosin. These proteins are involved in muscle contraction and movement.

9. Structural Proteins

They are fibrous and stringy and provide support. Examples include keratin, collagen, and elastin. Keratins strengthen protective coverings such as skin, hair, quills, feathers, horns, and beaks. Collagens and elastin provide support for connective tissues such as tendons and ligaments.

Good Sources of Protein

  • Eggs.

    A medium egg has around 6g of protein in an easily digestible form.
    They are loaded with vitamins, minerals, healthy fats, eye-protecting antioxidants and brain nutrients that most people don’t get enough of.
    Whole eggs are high in protein, but egg whites are almost pure protein.

    Protein content: 35% of calories in a whole egg. 1 large egg contains 6 grams of protein, with 78 calories.

  • Milk. Dairy foods are packed with protein and contain bone-building calcium, too.Milk is highly nutritious, but the problem is that a huge percentage of the world’s adults are intolerant to it.
    However, if you tolerate milk and enjoy drinking it, then milk can be an excellent source of high-quality protein.
    Milk contains a little bit of almost every single nutrient needed by the human body.
    It is particularly high in calcium, phosphorus and riboflavin (vitamin B2).
    Protein content: 21% of calories. 1 cup of whole milk contains 8 grams of protein, with 149 calories.
  • Yogurt. A combination of casein and whey protein, yogurt is a great protein-rich food.
    Protein content: Non-fat greek yogurt has protein at 48% of calories. One 170 gram (6 ounce) container has 17 grams of protein, with only 100 calories.
  • Fish and seafood.Fish is incredibly healthy, for various reasons.
    It is loaded with various important nutrients, and tends to be very high in heart-healthy omega-3 fatty acids.
    Protein content: Highly variable. Salmon is 46% protein, with 19 grams per 3 ounce (85 g) serving, with 175 calories.


    Shrimp is a type of seafood.
    It is low in calories, but loaded with various nutrients, including selenium and vitamin B12.
    Like fish, shrimp also contains plenty of omega-3 fatty acids.
    Protein content: 90% of calories. A 3 ounce (85 g) serving contains 18 grams, with only 84 calories.

  • Almonds.Almonds are a popular type of tree nut.
    They are loaded with important nutrients, including fiber, vitamin E, manganese and magnesium.
    Protein content: 13% of calories. 6 grams per 1 ounce (28 g) serving, with 161 calories.
  • Soya
  • Tuna Fish.Tuna is a very popular type of fish.
    It is low in both fat and calories, so what we’re left with is mostly just protein.
    Like other fish, tuna is also very high in various nutrients and contains a decent amount of omega-3 fatty acids.
    Protein content: 94% of calories, in tuna canned in water. A cup (154) contains 39 grams of protein, with only 179 calories.
  • Pistachio nuts and Peanuts. Peanuts are incredibly delicious.
    They are high in protein, fiber, magnesium and many studies show that they can help you lose weight.
    Peanut butter is also high in protein, just make sure not to eat too much as it is quite “more-ish.”
    Protein content: 16% of calories. One ounce (28 g) contains 7 grams, with 159 calories.
  • Lean Beef. Lean beef is very high in protein, and also tastes delicious.
    It is loaded with highly bioavailable iron, vitamin B12 and numerous other nutrients.
    Protein content: 53% of calories. One 3 ounce (85 g) serving of cooked beef with 10% fat contains 22 grams of protein, with 184 calories.
  • Chicken Breast.Chicken breast is one of the most popular protein-rich foods.
    If you eat it without the skin, the majority of the calories in it come from protein.
    Chicken breast is also very easy to cook, and tastes delicious if you do it right.
    Protein content: 80% of calories. 1 roasted chicken breast without skin contains 53 grams, with only 284 calories.
  • Turkey Breast. Turkey breast is similar to chicken breast in many ways.
    It consists mostly of protein, with very little fat and calories. It also tastes delicious.
    Protein content: 70% of calories. One 3 ounce (85 g) serving contains 24 grams, with 146 calories.
  • Oats.Oats are among the healthiest grains on the planet.
    They are loaded with healthy fibers, magnesium, manganese, thiamin (vitamin B1) and several other nutrients.
    Protein content: 15% of calories. Half a cup of raw oats contains 13 grams, with 303 calories.

How Much Protein Do You Need?

  • Teenage boys and active men can get all the protein they need from three daily servings for a total of seven ounces.

  • For children age 2 to 6, most women, and some older people, the government recommends two daily servings for a total of five ounces.

  • For older children, teen girls, active women, and most men, the guidelines give the nod to two daily servings for a total of six ounces.

Health Benefits of Protein


  1. Helps Improve Muscle Mass – Eating enough protein is necessary to build and maintain healthy muscle mass, while also supporting tendon, ligaments and other body tissue.
  2. Lowers Blood Pressure – A higher protein intake has been found to reduce blood pressure in individuals with Hypertension.
  3. Healthy Skin – Proteins are also responsible for extending mechanical support and strength to various tissues which suffer from constant wear and tear such as skin. Collagen is an important and abundant fibrous protein which provides strength to the cells, tissues and organ such as skin which needs to be revitalized on a continuous basis.
  4. Better Sleep – High protein diets have been found to help people sleep better and to wake up less frequently during the night as compared with high-carb diet.
  5. Healthy Hair – Proteins helps in maintaining healthy hair and protects them from damage. Studies conducted in this regard have advocated the role of proteins as a modulator of hair growth.
  6. Nerve Signaling – Another important task performed by proteins is the smooth functioning of nervous system. The nervous system of the body is activated whenever it is triggered and in turn responds with an appropriate reaction.
  7. Helps maintain strong bones – Many studies now show that a positive association exists between eating more foods with protein and better bone health.  The effects of protein on bones also relates to the specific protein foods being eaten and intake of important bone-building nutrients like calcium and magnesium. A diet high in protein from whole, nutrient-rich foods can heal broken bones, prevent bone weakness, fractures and even osteoporosis by increasing calcium absorption and helping with bone metabolism.
  8. Better Brain Function – Protein are vital brain foods. Eating high quality protein foods from animal sources provides the building blocks to make chemical messengers involved in wakefulness, hunger, energy production, motivation and optimal cognition function properly.
  9. Helps improve your mood – Certain amino acids from protein foods are needed to balance hormones naturally, control your mood and act as a natural remedy for anxiety. Proteins help neurotransmitters function and synthesize hormones like dopamine and serotonin that calm us and keep our outlook positive.
  10. Faster recovery from Injury – Greater protein synthesis accelerates the repair of tissue and strengthens connective tissue for less risk of injury.
  11. Less Belly fat
  12. Greater Muscle development – Proteins play an important role in muscle contraction and coordination. Proteins are present in the muscle tissues in the form of many microfilaments and provide muscle structure. Muscle growth depends on the adequacy of proteins in the body.

Protein Deficiency

This is the lack or insufficiency of Protein in the Body. A condition where amounts of proteins in the system is too low to meet minimum standard of health.

  • Marasmus – Marasmus is a severe lack of important nutrients. This is a fatal disease that causes weight-loss and dehydration.
  • Kwashiorkor – Lack of proteins from carbohydrates sources like rice, yams, and bananas causes kwashiorkor. This is a severe malnutrition disease common in older children. It also has symptoms common to marasmus such as irritability, diarrhea, fatigue, limited growth and cognitive development as well as mental health.
  • Protein C and Protein S Deficiency – Protein C & S deficiency are hereditary diseases that cause abnormal blood clotting. Such deficiencies are characterized by pain, redness, swelling and tenderness in the affected region
  • Cachexia – Cachexia is a condition that involves protein deficiency, depletion of skeletal muscle and an increased rate of protein degradation.

General symptoms of Protein Deficiency

  • Weak and sore muscles
  • Increased water retention
  • Flakiness, dry skin and rashes
  • Lethargy
  • Weight loss
  • Anxiety
  • Nausea
  • Skin ulcers
  • Bed sores
  • Deep line formations around the toes and nails
  • Stubborn wounds that do not heal
  • Constant headaches
  • Insomnia
  • Moody feelings
  • Blackouts
  • Depression
  • Skin color changes


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