Enzymes! …They’re everywhere! (video #1)

What are they? Protein catalysts: speed up chemical reactions without being consumed Their names often end in “ase” (lipase, amylase, catalase) …demo time!

What do they do? reactant molecules must collide with enough force (ENERGY!) and with the correct geometric orientation for bond breaking to occur

Where does the energy come from? proteins are denatured at high temperatures, so living cells cannot rely on high levels of heat as a source of activation energy (*note: activation energy is the energy that must be overcome for a chemical reaction to occur) catalysts allow reactions to proceed at suitable rates at moderate temperatures by reducing the activation energy(EA) barrier ( see fig.1 Pg.69 ) (video #2)

The substrate: Is the reactant that an enzyme acts on It binds (attaches) to a particular site on the enzyme (active site)and this is where catalysis occurs They fit closely into active sites because enzymes can adjust their shapes slightly to accommodate the substrate This is referred to as ‘induced fit’ and forms the enzyme- substrate complex (see fig.3 Pg.70) (video #3 + 4)

Conditions that help the enzymes work best… enzyme-catalyzed reactions can be saturated (the speed at which a catalyzed reaction proceeds cannot increase indefinitely by increasing the conc. of the substrate) every enzyme has an optimal temperature and pH that it works best at some enzymes also require either nonprotein cofactors, such as inorganic substances(Zn2+ and Mn2+ ) or organic coenzymes, (many vitamins) before they can work properly

Things that inhibit enzymes Inhibitors are chemicals that bind to specific enzymes this results in a change in the shape of enzyme and shuts it down

There are 2 kinds of inhibition: non-competitive – an inhibitor molecule binds to the enzyme at a site known as the allosteric site. as a result the 3-D structure of the enzyme is changed, which prevents the substrate form binding to the active site molecules that promote the action of enzymes can also bind to allosteric site – they are called activators

competitive inhibition involves chemical compounds that bind to the active site of the enzyme and inhibit enzymatic reactions the compounds compete with the true substrate for access to the active site i.e penicillin

Video #4

Industrial uses of enzymes users – starch processing industry enzymatic hydrolysis is used. amylase, produced by the bacterium Bacillus licheniformis, hydrolyzes starch to maltose then the enzyme glucoamylase, produced by moulds like Rhizopus, is added to hydrolyse maltose into glucose the dairy industry uses protein-hydrolyzing enzymes called proteases – used to coagulate milk for the manufacture of cheese

More Uses fat-hydrolyzing enzymes are used to develop characteristic cheeses like Romano enzymes ( proteases and amylases) are also used in the cleaning industry – they allow stains to be removed at lower temperatures and with less mechanical agitation (see Pg.76)