Chp 11 - Enzyme Kinetics

Biochem Exam 2

Vmax =

maximum velocity

Kcat =

turnover number

Km =

Michaelis constant

where does this graph reach equilibrium? what does this mean?

• this graph reaches equilibrium when both the reactant and product level off

• this means that the forward and reverse reactions are occurring at a fixed rate (equal rate)

V₀ = (what is it)

the initial velocity

the initial velocity is the _____ at which the substrate is becoming the product at the _______ of the reaction

speed, beginning

when does the enzymatic reaction reach the maximum velocity?

the enzymatic reaction reaches maximum velocity when the enzyme is saturated with substrate

what does it mean if the enzyme is saturated with substrate?

all of the enzymes active sites are filled and rxn is running at its absolute max speed

Vmax _______ with the amount of enzyme used in the rxn

varies

using more enzyme in a rxn ________ the maximal velocity

increases

Vmax depends on the ________ of enzyme

amount

Kcat = (what is the equation)

Vmax / [Enzyme]

Kcat is a _______ and a _______ ________

constant, turnover number

Kcat definition

the maximum number of substrate molecules converted to product on a single active site per second

equation for V₀

K _M is a ________ substrate concentration

specific

K _M is called…

Michaelis constant

what is Michaelis constant (K _M)? how would you describe?

it is the substrate concentration required to get to Vmax/2

K _M is _________ related to affinity

inversely

higher K _M means a _____ affinity of enzyme to its substrate

lower (think about the graph!!!)

lower K _M means a ________ affinity of enzyme to its substrate

higher (think about the graph!!!)

K_M value is approximately equal to…

the substrate concentration of the enzyme in vivo (in the body)

K_M values for enzymes ____ widely

vary

slide 10- slide 12

what three things can enzyme activity be modulated by?

1. temperature

2. pH

3. specific molecules (inhibitors)

enzyme activity __________ with temperature until the enzyme is _________

temperature, denatured

most enzymes have an _______ ___

optimal pH

the pH dependence of enzymes is due to the presence of…

ionizable R groups

inhibitors are compounds that _______ an enzyme’s activity

decrease

inhibitors can be ________ or __________

irreversible, reversible

irreversible inhibitors __________ the enzyme

inactivate