Enzymes are produced inside of cells

Increase chemical reactions inside & outside of cells

Chemical reaction: Reactants (substrates) --> Enzymes (catalyst: enable & speed-up reaction) --> products

Reactants absorb energy (energy of activation) from the environment for reaction to occur --> in living organism: cannot apply heat beyond living temperature --> energy of activation must be lowered --> through use of enzymes

Enzymes lower required energy of activation for biochemical reactions

Enzyme names (-ase): e.g. prote-ase breaks down proteins

Enzyme: has an active site to fit only one substrate --> very small

Models of fitting substrates:

1) Lock-Key model: substrate fits into enzyme active site --> enzyme-substrate complex --> products

2) Induced-Fit model: enzyme changes shape to fit substrate --> enzyme-substrate complex --> products

Enzymes:

breaks bonds of substrate

bonds substrate molecules --> bring them close enough for them to form bonds between them

Enzymes are reusable: small concentration in cells need --> due to their high efficiency & reusability

Factors affecting activity of enzymes:

1) temperature: substrates & enzymes contact more frequently --> but Optimum temperature exists --> beyond which, enzymes change shape of active site --> no reaction possible

2) Enzyme concentration: increases substrate reactions --> until all substrates all occupied --> beyod which, adding more enzymes, no increase in reaction

3) Substrate concentration: same for a fixed no. (concentration) of enzymes

4) pH: different enzymes, different optimal pH --> Pepsin (<7) in stomach --> digestive Trypsin (>7)

5) Acidity: high acidity preserves dead bodies --> since decomposing enzymes are not active

6) Cofactors: a non-protein addition (vitamin or mineral) that is required for the activity of some enzymes --> if enzymes are coenzymes, helps in reactions

7) Presence of inhibitor molecules: inhibits enzymes --> binds to enzyme --> enzyme changes shape --> inhibit enzyme activities

8) Allosteric enzyme: with allosteric site bond by allosteric inhibitor

9) Competitive inhibitor: e.g. Penicilin blocks active site that bacteria use to make cell walls --> blocks enzyme active site

10) Some allosteric enzyme requires its allosteric site to be bonded by allosteric activator in order to become active --> ensuring that the enzyme remains active rather than inactive states

11) Cooperativity: in multi-subunit enzyme (many active sites), if one unit binds to a substrate, other units also starts binding

12) Metabolic pathway: enzyme enables compound to be built up or broke down --> once some compounds have been formed --> use feedback inhibition --> to limit enzyme activity --> controlling compound concentration