Proteins

• Carbon • Hydrogen • Oxygen • Nitrogen

• Sulphur • Phosphorus

an amino acid

polypeptide chain of amino amino acids

All Amino Acids have the same basic structure, attached to a carbon there is : • An amino group - NH2 at one end of the terminal - The N Terminal • A carboxyl group - COOH at the other end of the terminal - The C Terminal • A hyrdrogen atom • The R group (which is different in each amino acid)

20 different amino acids are used to make up proteins

The specific sequence of Amino Acids in the polypeptide chain (Primary Structure)

There are thousands of different types of protein and their shape is determined by the specific sequence of Amino acids

• Enzymes are biological catalysts which speed up the rate of reaction • Carrier proteins transport materials across cell membranes • Cell membrane (phospholipid bilayer with carrier proteins) • Antibodies defend the body against disease causing microbes • Structural proteins support cells and tissues • Hormones transmit information • Contractile proteins such as ACTIN and MYOSIN bring about contraction in muscle • Transport proteins such as haemoglobin carry oxygen.

A protein is composed of the elements: • Carbon • Hydrogen • Oxygen • Nitrogen • &…may also contain Sulpher/Phosphorus A protein is: • A polymer • Made up of monomers, called Amino Acids • Which are organised in linear chains, called polypeptides There are approximately 20 amino acids used to make up proteins. There are thousands of different types of proteins and their shape is determined by the specific sequence of amino acids in the chain

amphoteric

When an Amino Acid forms a protein there is still an Amino Group at one end and a carboxyl group at the other end. The protein can therefore accept or give up hydrogen ions just like an Amino Acid This gives the protein the ability to resist changes in pH and act as a buffer

zwitterion ZWITT ER ION

• At Ph7, the Ph of the cell…. • The Amino Acid gains an H and becomes +vly charged. • The carboxyl group is acidic and at pH7 , it loses an H becoming negativly charged • So….At pH7 there is a positevly charged side and a negativly charged side

The chemical bond formed by a condensation reaction between the amino acid group of one amino acid and the carboxyl group of another amino acid

• A protein is a linear sequence of amino acids • A condensation reaction occurs between the amino group of of one amino acid and the carboxyl group of another amino acid • Resulting in the loss of a molecule of water • The chemical bond that forms as a result of this process is called a PEPTIDE BOND • When 2 amino acids are joined together by a peptide bond they are called a DIPEPTIDE

The primary structure of an amino acid is…. the sequence of amino acids in the polypeptide chain

The primary structure determines the shape and therefore function of the protein

The composition of the primary structure is determined by the base sequence of amino acids in one strand of the DNA molecule

The primary structure of an amino acid is…. the sequence of amino acids in the polypeptide chain It is determined by the base sequence of one strand of a DNA molecule The primary structure determines the shape and therefore function of the protein

The shape that polypeptide chains form as a result of hydrogen bonding, between the =O on -CO groups and the -H on NH groups, in the peptide bonds along the chain e.g. A spiral alpha helix or a less common Beta pleated sheet

• Alpha helix • e.g. Keratin • Beta pleated sheet (Less common) • e.g. Fibroin, in silk, has a high proption of Beta pleated sheet