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How does the primary sequence of a protein dictate its structure and function?

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Introduction

Biology How does the primary sequence of a protein dictate its structure and function? * Explain all the different types of structures. * Use a range of proteins stating their functions linking back to their primary structure. * Use diagrams. First discovered in 1838, proteins are complex organic compounds containing the elements carbon, hydrogen, oxygen, nitrogen and sometimes sulphur. Other proteins can also form complexes with other molecules containing phosphorus, iron, zinc and copper. These are known as prosthetic groups. Proteins are macromolecules of high relative molecular mass (between several thousand and million) consisting of chains of amino acids. There are twenty different types of amino acids, as shown below with their chemical structure. These can be classified into three groups. These are polar, non polar and charged. Polar and charged amino acids will often be found on the surface of the protein interacting with the surrounding water (hydrophilic). Non polar (hydrophobic) amino acids will bury themselves in the interior. Amino acids are primary amines that contain an alpha carbon that is connected to an amino (NH3) group, a carboxyl group (COOH) and a variable side group (R) - amino acids shown above. This side group gives each amino acid a distinctive property and function. Linking an amino group to a carboxyl group on another amino acid then creates polymers. This is known as a peptide bond forming polypeptide chains by a condensation reaction. ...read more.

Middle

The H atom of the NH group of one amino acid is bonded to the O atom of the CO group three amino acids away. The second are sulfhydryl linkages. Theses are covalent bonds between cysteine groups. Cysteine has a sulphur group available for binding to other groups. Often in proteins, adjacent sulfhydryl groups on cysteins will form a covalent link in a protein, which makes them crucial for a protein to perform its function. The chemical structure of a sulhydryl bond A sulfhydryl bond in a peptide Others include hydrophobic interactions and ionic interactions. Proteins will often have stretches of amino acids that will show two common secondary structures. These are the alpha helix and the beta (pleated) sheets. The hydrogen bonding and the hydrophobic interactions between amino acids in the protein decide the formation of these structures. The alpha helix is shown as a ribbon (ball and stick diagram) of amino acids. This structure is very stable and flexible and is often seen in parts of a protein that may need to bend or move. Ribbon Ball and stick A protein that is entirely alpha-helical is also called fibrous. In the beta pleated sheet, two planes of amino acids will form, lining up in such a way that hydrogen bonds can form between facing amino acids in each sheet. The beta sheet is different then the alpha helix in those far distant amino acids in the protein can come together to form this structure. ...read more.

Conclusion

They are responsible for metabolism and its regulation, these molecules have catalytic sites on which substrate fits in a lock-and-key to trigger and control metabolism throughout the body. Protein hormones come from the endocrine glands and do not act as enzymes. Instead they stimulate target organs that which control important activities, for example, the rate of metabolism and the production of digestive enzymes and milk. Insulin, secreted by the islets of Langerhans, regulates carbohydrate metabolism by controlling blood glucose levels. Thyroglobulin, from the thyroid gland, regulates overall metabolism and calcitonin, also from the thyroid, lowers blood calcium levels. Antibodies (immunoglobulins) make up the thousands of different proteins that are generated in the blood serum in reaction to antigens (body-invading substances or organisms). A single antigen may bring out the production of many antibodies, which combine with different sites on the antigen molecule, neutralize it, and cause it to precipitate from the blood. Myoglobin and haemoglobin are known as conjugated as they have a prosthetic group (non protein) group attached to them. Haemoglobin consists of four separate polypeptide chains of two types, each with an individual prosthetic group. Generally it has two alpha chains and two beta chains. The two alpha chains each contain 141 amino acids and the two beta chains each contain 146 amino acids. The function of haemoglobin is transport oxygen to vertebrate blood. Myoglobin consists only of one polypeptide chain containing one prosthetic group - iron. Myoglobin is another oxygen carrier found mainly in muscles. ?? ?? ?? ?? Waseem Munir Page 1 ...read more.

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