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Amino Acids...
The smallest units(monomers) of a protein, feature an amino and carboxyl group, connected by R-C-H. "R" is a variable that can be different atoms.
Polypeptides...
A polypeptide is the primary structure of a protein. The sequence of the amino acids within a polypeptide is determined by genetic code.
Polypeptides are polymers built of amino acid monomers during a condensation reaction. The amino group, (NH2) of one amino acids, and the carboxyl group (COOH) of another form a peptide bond, forming a dipeptide. This can continue to from a string of amino acids, called a polypeptide.
Building a protein...
A polypeptide becomes a protein when it folds and connects to itself, or to other polypeptides.
Primary structure
Amino acids form a sequence, known as a polypeptide.
Secondary structure (Now a protein)
The polypeptide beings to coil up and bond with itself through hydrogen bonds.
Tertiary (3rd Level) Structure
Secondary structures fold over once more and Ionic bonds and disulfide bridges form.
Quaternary (4th Level) Structure
Quaternary structures are composed of two or more linked polypeptides.
Functions of proteins...
The function of a protein is determined by the shape of its molecule. Proteins are divided into two main types: globular and fibrous proteins.
| Protein | Function |
|---|---|
| Rubisco | An enzyme involved in carbon fixation in photosynthesis. |
| Insulin | A hormone produced by the pancreas which stimulates the liver to take up glucose from the blood and store it as glycogen. |
| Immunoglobulin | A large protein (antibody) produced by the immune system to fight infection. |
| Rhodopsin | A protein linked to a pigment found in the photoreceptor cells in the retina of the eye. |
| Collagen | A structural protein which builds muscle, tendons, ligaments and the skin of vertebrates. |
| Spider silk | A strong and elastic fibrous protein created by spiders to form their webs. |
Denaturation...
Denaturation is an irreversible process when a protein loses it's form due to a PH or Temperature outside it's operating range. The primary structure of the protein will usually remain but secondary, tertiary and quaternary structures are usually lost.
For example enzymes, which are tertiary proteins, are easily denatured by extremes of pH or temperature and lose the ability to function as catalysts.