Biochem Exam 1 CHP 6

• Biological Catalyst (increases rate of reaction without being consumed in reaction)

• All are proteins

enzymes

E + S →

ES → P

Specific site on/in the enzyme where substrate binds, and catalysis takes place is called the…

active site

substrate binds to that portion of the enzyme with a complementary shape.

lock and key model

binding of the substrate induces a change in the conformation of the enzyme that results in a complementary fit. More common model.

induced fit model

catalytic power=

rate enhancement= catalyzed rate/uncatalyzed rate

What is the formula for rate law

rate= k[A][B]

Enzyme catalyzed reactions can exhibit zero order kinetics when…

the enzymes active site is saturated with substrate

the enzyme concentration is constant and the rate of these reactions is dependent on the concentration of substrate(usually happens at low substrate concentration)

1st order reaction

what is the Michaelis-Menten Model

V= delta P/ delta t

(k-1+k2)/k1 = km

Vinit=

V[max]S/Km+S

A lower Km indicates…

tighter binding

What is the turnover number

kcat= vmax/[Etotal]

a higher Kcat indicates…

higher enzyme turnover

catalytic efficency=

kcat/km

what is the linewaver burke equation

y=mx+b

1/v =

(km/vmax) x (1/s) + (1/vmax)

inactivators that react with the enzyme to permanently inactivate the enzyme

irreversible inhibitor

• bind to and can dissociate from the enzyme

• They are often structural analogs of substrates or products and are used as drugs

to slow down a specific enzyme

reversible inhibitor

• bind to the active (catalytic) siteand blocks access to it by substrate.

• Binding occurs to the free enzyme.

competitive inhibitor

• bind to a site other than the active site; inhibits the enzyme by changing its conformation.

• Binding occurs either to the free enzyme or to the enzyme-substrate complex

non competitive inhibtor

What happens when there is an inhibitor present

Km increases

The binding of the inhibitor does not affect binding of the substrate (no change to KM) but it does inhibit the enzyme’s catalysis (Vmax decreases)

pure non competive

The binding of the inhibitor can affect the binding of substrate (KM changes) and inhibit the enzyme’s catalysis (Vmax decreases)

Mixed non-competitive

while the substrate binds to the active site the inhibitor binds to the _______ site

allosteric

What changes in a competitive inhibitor?

slope/ x intercept

What changes in a pure non competitive inhibitor?

y intercept, slope

What changes in a mixed non competitive inhibitor?

everything

What changes in an uncompetitive inhibitor?

y intercept, x intercept