Enzymes

Protein nature of ENZYMES

• METABOLISM=ALL THE REACTIONS OF THE BODY
• Reactions occur in a sequences called metabolic pathways
• Metabolic Pathways=A sequence of enzyme-controlled reactions in which a product of one reaction is a reactant in the next.
• ANABOLIC REACTIONS=BUILDING UP MOLECULES
• E.G PROTEIN SYNTHESIS
• CATABOLIC REACTIONS=BREAKING MOLECULES DOWN
• E.G DIGESTION
• METABOLIC PATHWAYS ARE CONTROLLED BY ENZYMES
• The products of one enzyme-controlled reaction become the reactants in the next

Properties of ENZYMES

• Enzymes are GLOBULAR PROTEINS
• Globular proteins that are CATALYSTS
• CATALYSTS
• A molecule which speeds up a chemical reaction.
• Molecule remains unchanged at the end of the reaction.
• 'BIOLOGICAL' catalysts enzymes are because they are made by living cells.
• Enzymes and chemical catalysts share properties in the reactions they catalyse:
• ENZYMES...
• 1.)Speed up reactions
• 2.)Are NOT used up
• 3.)Are NOT CHANGED
• 4.)Have a high turn-over number
• i.e they catalyse many reactions per second
• NO ENZYMES=Reactions in cell would be far too slow to be compatible with life.

ENZYMES...

• Enzymes ONLY catalyse reactions=energetically favourable/WOULD HAPPEN ANYWAY.

STRUCTURE of ENZYMES(PROTEINS)

• Enzymes=PROTEINS
• PROTEINS=TERTIARY STRUCTURE
• PROTEIN CHAIN=FOLDS INTO A SPHERICAL 'GLOBULAR' SHAPE
• GLOBULAR SHAPE=WITH HYDROPHILIC R GROUPS ON THE OUTSIDE OF THE MOLECULE
• R GROUPS(OUTSIDE OF MOLECULE)HYDROPHILIC=MAKING ENZYMES SOLUBLE
• Each enzyme has a particular sequence of amino acids
• Each enzyme has different elements in the R groups
• Element in the R group=determine the bonds the amino acids make with each other
• 3 different types of BONDS:IONIC BONDS-HYDROGEN BONDS-DISULPHIDE BRIDGES
• Bonds=HOLDE THE ENZYME MOLECULE IN ITS TERTIARY FORM
• BONDS MAINTAIN ENZYME'S SHAPE
• Small area with a SPECIFIC 3D shape is the active site
• The ACTIVE SITE gives the enzyme many of it properties
• Chemical bonds=VARY IN STRENGTH
• Hydrogen bonds=weak
• lots of hydrogen bonds=stronger(significant binding effect)
• Ionic bonds and covalent bonds(disulphide bond) are stronger than hydrogen bonds

Where do enzymes act?

• EXTRACELLULAR
• INTRACELLULAR,IN SOLUTION
• INTRACELLULAR,MEMBRANE BOUND

PROTEIN STRUCTURE

• DIFFERENT LEVELS OF ORGANISATION
• PRIMARY
• SECONDARY
• TERTIARY
• QUATERNARY
• 4 STRUCTURES

Primary Structure

• ORDER OF AMINO ACIDS IN A POLYPEPTIDE CHAIN
• POLYPEPTIDE=20 DIFFERENT TYPES OF AMINO ACIDS IN A POLYPEPTIDE CHAIN
• AMINO ACIDS=can be joined in any order,number,combination(huge number of polypeptide POSSIBLE)
• primary structure is determined by the base sequence on one strand of the DNA molecule.
• POLYPEPTIDE=a linear organic polymer consisting of a large number of amino-acids bonded together in a chain forming part or whole of a protein molecule.
• polypeptides have up to 20 different types of amino acids
• these amino acids can be joined in any order in any number and combination(huge number of possible polypeptides
• primary structure is determined by the base sequence on ONE STRAND OF THE DNA MOLECULE

SECONDARY STRUCTURE