Protein molecule

Protein Molecule

A protein molecule is a complex, high-molecular-weight organic compound that consists of amino acids arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acids. Proteins are fundamental components of all living cells and include many substances, such as enzymes, hormones, and antibodies, that are necessary for the proper functioning of an organism.

Structure

Proteins are made up of hundreds or thousands of monomers called amino acids. These amino acids are attached to one another in a sequence, forming a long chain. This chain of amino acids then folds into a unique shape. This shape is determined by the sequence of amino acids. In fact, even a slight change in this sequence can affect the protein's structure and its function.

Function

Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, responding to stimuli, providing structure to cells and organisms, 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.

Classification

Proteins can be classified into three general types: fibrous, globular, and membrane. Fibrous proteins provide structural support for cells and tissues. Globular proteins are generally compact, soluble, and spherical in shape. Membrane proteins are integral part of the cell membrane and function in transport, signal transduction, and cell adhesion.

Synthesis

Protein synthesis is the process by which proteins are produced, or synthesized, in living cells according to the instructions carried by DNA. The process of protein synthesis involves transcription and translation. During transcription, a DNA sequence is read by an RNA polymerase, which produces a complementary, antiparallel RNA strand. During translation, this RNA strand is read by a ribosome to produce a protein.

See Also

• Amino acid
• Peptide bond
• Enzyme
• Hormone
• Antibody
• DNA replication
• Cell membrane
• Transcription
• Translation