Biochemistry Lec. 6

standard free energy

difference between energies of reactants and products under standard conditions

G<0

spontaneous; energy released

G=0

equilibrium

G>0

nonspontaneous; energy released

change in free energy

G = H-TS

activation energy

the energy input required to initiate a reaction to reach transition state

transition state

intermediate stage in a reaction in which old break and new bonds form

catalysts

speed up reactions without being consumed

enzymes

increase the rate of a reaction

example of enzymes

urease

active site

where the substrate binds and where the reaction takes place

K_m = [S]

Vmax/2

low [S]

Vini = Vmax[S]/Km

high [S]

Vini = Vmax

V_ini

initial rate or velocity

V_max

maximum rate or velocity

[S]

substrate concentration

Km

Michaelis constant

Will increasing the temperature increase the rate?

Yes, it will increase the energy available to the reactants to reach the transition state

chymotrypsin

an enzyme that catalyzes the hydrolysis of peptide bonds

substrate

compound which is catalyzed by the enzyme

active site

where the substrate binds

apoenzyme

protein portion

cofactor

nonprotein portion

coenzyme

nonprotein organic molecule

lock and key

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

induced fit

binding changes the shape of the enzyme to result in a complementary shape

activation

initiates or increases the activity of an enzyme

inhibition

makes an active enzyme less active or inactive

competitive inhibitor

binds to the active site of an enzyme preventing binding of substrate

noncompetitive inhibitor

binds to a portion of the enzyme other then the active site inhibiting activity of the enzyme

How can enzymes be regulated?

• feedback control

• proenzymes

• allosterism

• protein modification