Enzyme catalysis

Question 1

what are enzymes usually made of

Answer 1

proteins, sometimes RNA

Question 2

enzymes are biological catalysts…

Answer 2

ctalyse reactions under biologically relevant conditoins - about 37*C, neutral pH (except stomach, lysozymes…) and 10^-6 to 10^-3M

Question 3

can the active site have prosthetic groups

Answer 3

yes

Question 4

how do enzymes work

Answer 4

A+B A.B [transition state] C.D C+D

Question 5

describe transition state

Answer 5

between reactants and products. highest energy!

Question 6

describe induced fit model

Answer 6

active site changes shape to accomodate for substrate. Then, it changes shape to help form the transition state, lowering the transition state’s energy, hence lowering the energy of the reaction

Question 7

describe dfiference in energy profile diagrams for catalysed vs uncatalysed

Answer 7

uncatalysed has 3 bumps, top of middle one represents transition state, bottom of middle one represents A.B and C.D

Question 8

How do we get Michaelis Menten Curve

Answer 8

First, we plot product concentration against time for various concentrations of a product.
We calculate the initial velocity
Then we plot initial velocity against substrate concentration.

Question 9

describe Vmax

Answer 9

Varies with temperature and concentration: doubled conc = doubled V max.
Ms-1

Question 10

describe Km

Answer 10

conc @ 1/2 Vmax
independent of concentration
M
increased Km = decreased enzyme affinity.

Question 11

michaelis menten curve equation?

Answer 11

Vmax[s]/(Km + [s])

Question 12

what are the axes and intercepts for Lineweaver Burk plot?

Answer 12

y axis: 1/[Vo]
x axis: 1/[S]
Y int: 1/Vmax
X int: -1/Km

Question 13

what is irreversible inhibition

Answer 13

substrate binds covalently to active site. Inhibits enzyme permanently

Question 14

what is reversible inhibition

Answer 14

substrate binds non covalently to enzyme, not necessarily at the active site.

Question 15

3 types of reversible inhibition?

Answer 15

competitive inhibition
uncompepitivie inhibition
mixed/non competitive inhibition

Question 16

describe competitive inhibition

Answer 16

inhibitor binds non covalently to active site.
V max unchanged.
Km increases

Question 17

describe non competitive inhibition

Answer 17

inhibitor binds non covalently to ENZYME SUBSTRATE COMPLEX
Forms parallel lines.
As [I] Increases, 1/Vmax increasses (therefore Vmax decreases)
As [I] increases, -1/Km increases in magnitude (wherefore m decreases)

Question 18

describe mixed inhibition

Answer 18

inhibitor binds non covalently to enzyme substrate complex or to the enzyme on its own (not the active site though).
Vmax decreases
Km can increase or decrease.

Question 19

what are isozymes

Answer 19

enzymes that catalyse the same reaction but have different primary structures.
Often occur in different tissues, and produced by different genes

Question 20

describe allosteric enzymes

Answer 20

binding of a modulator to the enzyme changes its shape and functionality. therefore, its kinetics differ from michaelus menten model.