Catalysis

enzymes

Globular

Monomeric enzymes have only one polypeptide chain whereas oligomeric enzymes have several polypeptide chains

Joins two molecules together by a dehydration (condensation) reaction

Transfers a phosphate group to another molecule eg carbohydrate or protein

It adds nucleotide monomers in sequence (by condensation) to a polymer eg DNA or RNA (by a phosphodiester bond)

It joins two strands of nucleic acid polymer (by condensation creating a phosphodiester bond)

Catalyse a hydrolysis reaction

Hydrolyses a peptide bond to break down protein into animo acids eg pepsin and trypsin

Hydrolyses phosphodiester bonds to break down nucleic acids into nucleotides eg restriction enzymes such as Eco R1

Hydrolyses phosphodiester bonds in ATP to form ADP + Pi eg sodium-potassium pump

Removes a phosphate from a molecule by hydrolysis

activation energy

By binding to two substrates to force them close together or by stressing the chemical bonds in the molecule to break them down

conformational

Induced fit

The amino acid sequence of the enzyme

When an inhibitor binds to the enzymes active site preventing substrate binding

When an inhibitor binds to a second (differenct) site on the enzyme resulting in a conformational change of the enzyme and preventing substrate binding

Enzymes that have two conformations - one which is active and one which is not

regulating

Activators have a positive effect by stabilising the enzymes active form whereas inhibitors have a negative effect by stablilising the enzymes inactive form

The addition or removal of chemical groups on the enzyme

This is a form of negative feedback.  The end product of a biochemical pathway binds to the first enzyme (in the pathway) inhibiting it.  This prevents intermediates being made and reduce the amount of end product being made

Steriod hormones eg testosterone

These can diffuse across the plasma membrane of the target cell and activate gene regulatory proteins which regulate the transcription of specific genes

• Peptide hormones eg insulin
• Neurotransmitters eg noradrenalin and acetylcholine

These activate receptor proteins on the surface of the targer cell.  The receptors acts as transducers, converting the extracellular binding event into intracellular signals which alter the behaviour of the target cell