Proteins are complex organic compounds. The constituents that make up proteins are carbon, hydrogen, nitrogen, oxygen, and sulfur. Proteins are the only source of nitrogen in our body.
Proteins are made up of polymers of amino acids. The amino acids are joined by peptide bonds that are broken down when hydrolyzed with an acid or a protease enzyme. It is the sequence of amino acids that determines the function of the protein. In all, there are 20 amino acids, out of which nine are called essential amino acids. These essential amino acids cannot be synthesized by the human body; we get them from the food we eat.
Protein structures are classified into four categories, namely primary, secondary, tertiary, and quaternary. This classification is based on the arrangement of the amino acid subunits. Structures of proteins can shift from one form to another for performing particular functions. Proteins can also be covalently bonded with carbohydrates. Molecules containing proteins and carbohydrates are called glycoproteins. They play an important role in the functioning of the body's immune system.
♦ All of us are aware of the fact that proteins are the building blocks of the body. Our body needs protein for the growth and repair of the tissues and muscles. In short, we can't do anything without protein. Every cell of the human body contains protein in their structure. It is present in the skin, hair, nails, teeth, muscles, bones, ligaments, tendons, and organs of the body. All the body fluids, except bile and urine contain proteins.
♦ Proteins are one of the important constituents of the red blood cells, hemoglobin (which comes from heme meaning iron and globin meaning proteins). About 97% of the dry content of red blood cells is made of proteins. There are also transmembrane proteins that help in the transport of biological molecules and substances across the membrane.
♦ Proteins form an essential part of a balanced diet. During digestion, the proteins from the food are broken down into their constituent amino acids. These amino acids are absorbed by the blood and are transported to the liver, where further synthesis of proteins takes place and they are stored as fat or glycogen in the body.
♦ Every person needs 0.8 g of protein per kilogram of his/her body weight. For example, if a person weighs 80 kilograms, then his everyday diet should contain 64 g of protein. It is estimated that 1 gram of protein contains 4 calories of energy. One should consume diets rich in protein such as pulses, eggs, milk, and dairy products. However, overconsumption of proteins is harmful as it can strain the liver and kidney due to excessive protein catabolism.
♦ When the body is deprived of glucose (the most important energy fuel), it starts using the stored fats and proteins as an energy source. Excess catabolism of proteins is harmful as it can weaken the immune system at a certain stage.
♦ Do you know about the factor responsible for biochemical reactions in the body? Well, it's none other than enzymes. Enzymes are proteins made up of linear polymers of amino acids. All the biological cells require enzymes for all their processes. Enzymes help in breaking down the substrates into their respective products. A specific enzyme is responsible for a specific substrate and vice versa.
Proteins play a major role in the body's defense mechanism. In fact, antibodies are made up of proteins and are responsible for protecting the body against the harmful organisms such as bacteria, fungi, virus, and protozoa. An individual with a compromised immune system refers to a person whose body fails to produce adequate antibodies. Such people need to consume adequate amount of protein supplements to boost their immune system levels.