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Protein structure is the three-dimensional arrangement of atoms in an amino acid-chain molecule. Proteins are polymers – specifically polypeptides – formed from sequences of amino acids , which are the monomers of the polymer.
Proteins are often synthesized in an inactive precursor form; typically, an N-terminal or C-terminal segment blocks the active site of the protein, inhibiting its function. The protein is activated by cleaving off the inhibitory peptide. Some proteins even have the power to cleave themselves.
The only major component of most food which contains nitrogen is protein (fat, carbohydrate and dietary fiber do not contain nitrogen). If the amount of nitrogen is multiplied by a factor depending on the kinds of protein expected in the food the total protein can be determined. This value is known as the "crude protein" content.
Only proline differs from this basic structure as its side chain is cyclical, bonding to the amino group, limiting protein chain flexibility. [34] The side chains of the standard amino acids have a variety of chemical structures and properties, and it is the combined effect of all amino acids that determines its three-dimensional structure and ...
Biomolecular structure is the intricate folded, three-dimensional shape that is formed by a molecule of protein, DNA, or RNA, and that is important to its function.The structure of these molecules may be considered at any of several length scales ranging from the level of individual atoms to the relationships among entire protein subunits.
The single-stranded nature of protein molecules, together with their composition of 20 or more different amino acid building blocks, allows them to fold in to a vast number of different three-dimensional shapes, while providing binding pockets through which they can specifically interact with all manner of molecules.
Of the many hundreds of described amino acids, 22 are proteinogenic ("protein-building"). [23] [24] [25] It is these 22 compounds that combine to give a vast array of peptides and proteins assembled by ribosomes. [26] Non-proteinogenic or modified amino acids may arise from post-translational modification or during nonribosomal peptide synthesis.
Ribbon diagram of myoglobin bound to haem (sticks) and oxygen (red spheres) (Ribbon diagrams, also known as Richardson diagrams, are 3D schematic representations of protein structure and are one of the most common methods of protein depiction used today. The ribbon depicts the general course and organisation of the protein backbone in 3D and ...