Proteins: Complex Macromolecules

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Proteins are complex macromolecules that are formed by elements carbon, hydrogen, oxygen and nitrogen. Proteins composed of one or more polypeptide chains of amino acids. The main functions of proteins are to structure, support, protect, make movement, catalyst, transport and make hormones in human body. In the structural role, collagen and elastin provide support for connective tissue. Actin and myosin are proteins that involved in muscle contraction and movement. Haemoglobin is a protein that transports oxygen through the blood. For protection, there are immunoglobulins. Immunoglobins are glycoprotein molecules that are produced by plasma cells. It functions as antibodies. There are five types of immunoglobulins, which is IgG, IgA, IgM, IgD,…show more content…
Amino acids are the building blocks of proteins. All amino acids have the same basic structure but differ in their R-side chains. Each amino acid consists of an amino group (-NH3), a carboxyl group (-COOH) and a hydrogen atom (H). The amino and carboxyl groups are attached to a central alpha carbon together with a hydrogen atom and an R-side chain. There are currently known that over 170 amino acids occur in organisms but only 20 are commonly found in proteins. R groups determine the chemical properties of the amino acids. The simplest amino acids have hydrocarbons as side chains which are neutral and non-polar or hydrophobic. They are not soluble in water. Amino acids with a polar R group are neutral and polar or hydrophilic. They are more soluble in water. Polar side chains can be uncharged or carry a negative or positive…show more content…
Structurally, proteins can be classified into two groups, which are fibrous proteins and globular proteins. The examples of fibrous proteins include collagen, elastin, and keratin which form body structured of animals. It is a stable protein structure which insoluble in water. Globular proteins include globulin, enzymes, antibodies, and hormones. It has a tertiary structure which folded in complex three-dimensional structures. Proteins, when classified according to their composition, are placed into two groups, which are simple proteins and conjugated proteins. Simple proteins are pure proteins that formed from amino acid residues only. For example, fibrous proteins and globular proteins. Conjugated proteins are a complex compound which is made up of a globular protein with non-protein components attached. Proteins can also be classified according to its quality. The high biological value of protein supplies all essential amino acid in the quantity form that we need. The lower biological value of protein is lack essential amino acid in the quantity form. There are common sources of protein in the diet, which is animal protein and plant protein. The example of the animal protein is casein in milk, albumin in eggs and whey in cheese while the example of plant protein is gluten in wheat and soya in the

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