2.5 enzymes

enzymes

globular protein that acts as a biological catalyst

activation energy Ea

the en barrier to be overcome for a rxn to occur & to form products

enz lowers Ea

signif to living organisms? slow rate of metabolic rxns at biological temps (37) → too slow to support demands → enzs lower Ea → rapid enough to support.

nature of enzs

can be reused, small amt req

specificity

enz catalysed rxn is reversible

readily denatured

active sites & proteins

specific 3d shape. shape of active site is complementary to substrate.

active site lined w aa residues & proteins → R groups bind to sub.

es complex: 2 models

lock & key — falsified (says only 1 enz to 1 sub, but actl can w similarly shaped subs)

induced-fit model — enz can slightly change its conformation to be more complementary to shape of the sub & return to org after.

enz activity

to note:

1. collisions, effective collisions

2. formation of es complex

3. rate of reaction

temp (KE, opt, denature)

ph: slight (alters charge of AA residues at active site → prevents formation of ES complex) vs large changes (denature)

sub conc (at high — all active sites occupied)

enz conc

denaturation

disruption of the 3d shape → loss of biological activity

bonds that maintain sec & tertiary structure are broken (H, ionic, disulphide). loses conformation

denatured, enz is non functional

immobilised enzs

advs: higher enz conc for higher rate, can be reused, resistant to denaturation over larger range of ph & temp

eg. lactose free milk: process — lactase from yeast, alginate beads, milk run over, lactose broken down, enzs can be reused

advs for milk: maintain org taste, reduce wastage. can be used as sweetener, shorten prod time for yogurt / cheese.

commercial applications: asia/africa, higher lactose intolerance