MOLECULES OF LIFE

Powerpoint Presentation: Proteins

Amino Acids and Proteins : elements C, H, O, N, S

Amino acids

amino group, carboxyl group, hydrogen and a variable side group (residue) each joined to a central carbon atom.

Amino end and carboxyl end can be ionised NH³⁺ and COO^- to give acidic and basic characteristics. At pH 7 both groups are ionised.

The residues are side chains which give the individual properties to the amino acid (acidic, basic, neutral and nonpolar).

Functions of amino acids:

• protein synthesis
• energy reserve
• hormones (thyroxin)

20 different amino acids used in protein synthesis though others do occur in nature.

Essential amino acids cannot be synthesised by the organism and must form part of their diet.

The peptide bond

Carboxyl group + amino group form a strong covalent bond releasing water in to process water = a condensation reaction (the reverse is hydrolysis).

Amino acids join together in a long chain: N terminal end to C terminal end = a polypeptide.

PROTEINS ARE FOLDED POLYPEPTIDES

Protein structure depends upon its amino acid sequence.

PROTEIN FUNCTIONS

Protein structure determines protein function. Denaturation or inhibition which may change protein structure will change its function. Coenzymes and cofactors in general may enhance the protein's structure.

• Fibrous proteins are involved in structure: tendons ligaments blood clots. (e.g. collagen and keratin). Contractile proteins in movement: muscle
• Globular proteins: most proteins which move around eg albumen, casein in milk. Proteins with binding sites: enzymes, haemoglobin, immunoglobulins (antibodies), membrane receptor sites.

Proteins can be classified by function:

• Introduction
• Carbohydrates
• Lipids
• Topic Chapters Index
• Top of Page

© Paul Billiet 2012