DNA nucleus double helix cytoplasm Base pairs copy gene amino acid protein A,G,C,T Ribosome Write the ledger for this diagram – include these words

Learning Outcome Protein folding Explain how one strand of mRNA can give rise to many proteins by …. –Pre-transplational modificayion (process of alternative RNA splicing) –Post-translational modification (cutting, combining polypeptide chains, addition of groups)

Why is shape important?

Protein shape and folding..... A string of amino acids (polypeptide chain) Charges on the amino acid causes hydrogen bonding either folds of coils

Further interactions between side chains (R group on amino acids)

Amino acids linked by peptide bonds to form polypeptide and then chains form 3D shapes of protein Amino Acids Polypeptide (chain of aa) Coils into helix Beta sheets Elastin proteinsFibril proteins Conjugated proteins Globular proteinsFibrous proteins

Proteins have a wide variety of structures and shapes resulting in a wide range of functions! Elastin proteins Fibril proteins Conjugated proteins Globular proteinsFibrous proteins Enzymes Antibodies Hormones & recpetors

Why is shape important?

Pre-translational Modification Alternative splicing

However, multiple introns may be spliced differently in different circumstances, for example in different tissues Heart muscle 1435 Uterine muscle Thus one gene can encode more than one protein. The proteins are similar but not identical and may have distinct properties. This is important in complex organisms

Post-Translation Modification 2 main methods of modification; Cutting/Cleavage Addition Cleavage

Cleavage and Cutting Some hormones are produced in an “immature” form, and require further cutting to get the active peptide hormone. Pro-hormones are cut into final form by peptidases (enzyme) in the Golgi apparatus. Cutting usually occurs at basic amino acids (lysine, arginine) Inhibin alpha processing

Molecular Addition Modification by adding different groups such as carbohydrate component (eg. glycoprotein for membrane)and phosphate group (eg. regulatory proteins such as p53) p53 is a tumour repressor protein – only needs to be active (with a phosphate group) if the cell DNA becomes damaged. When made for active form is needed phosphorylation occurs which adds a phosphate group. p53 then can either repair the DNA, or if not able then it causes programmed cell death (apoptosis)

Demonstrate your knowledge by summarising.....

Separating Proteins Process called electrophoresis Separates on charge and size Useful for analysis/identification and purification

Electrophoresis Definition Electro = Charge + Phorsesis= Carry Electrophoresis = Separation of charged molecules by differences in their rate of migration in an electric field.

Agarose Gel Mesh of gel sepeartes size Electrical Charge then placed across to separate.

Name 5 functions of proteins;

Enzymes Structural proteins Hormones Antibodies Associations with other chemicals