Chapter 1- Enzymes

Question 1

Catalysts

Answer 1

increase reaction rates by lowering the activation energy of a reaction.
Also reduce the energy of the transition state.
However, do not shift a chemical reaction or affect spontaneity

Question 2

Transition State

Answer 2

the unstable conformation between reactant and product

Question 3

Enzymes

Answer 3

act as biological catalysts binding to substrates (reactants) and converting them into products.
Bind to substrates at the active site.
Most enzymes are proteins.

Question 4

Specificity constant

Answer 4

measures how efficient an enzyme is at binding to the substrate and converting it to a product.
When Specificity constant is high the enzymes site will have a high substrate affinity.

Question 5

Induced fit theory

Answer 5

Enzyme active sites change their shape slightly when substrate binding occurs to fit

Question 6

Lock and key model

Answer 6

outdated theory of how substrate binds

Question 7

Ribozyme

Answer 7

non-protein enzyme

is a RNA molecule that is capable of acting as an enzyme by changing speed of reactions.

Question 8

Cofactor

Answer 8

non-protein molecule that helps enzymes perform reactions by donating or accepting electrons.

Question 9

Coenzymes

Answer 9

are organic cofactors

ex:vitamins

Question 10

Metal ions

Answer 10

are inorganic cofactors

ex: Iron (Fe2+), Magnesium (Mg2+)

Question 11

Holoenzymes

Answer 11

enzymes bound to their cofactor

Question 12

Apoenzyme

Answer 12

enzyme lacking its cofactor

Question 13

Prosthetic groups

Answer 13

are cofactors that tightly/covalently bind to their enzyme in a holoenzyme

Question 14

Protein enzymes

Answer 14

have optimal temperature &pH ranges. If not optimal, temp. and pH can denature protein enzymes resulting in loss of functionality.
DAT Tip: if temperature is around higher optimal range (not too high), this can increase enzymes function for faster reaction

Question 15

Competitive inhibition

Answer 15

form of enzyme regulation; inhibitors compete with substrates for active sites.
increasing substrate will result in better chance of substrate binding to active site - outcompete a competitive inhibitor by adding more substrate

Question 16

Enzyme saturation

Answer 16

as saturation of substrate reaches a high level, increased catalysis speed will plateau.

Question 17

Noncompetitive inhibition

Answer 17

when an inhibitor binds to the allosteric site (different site than the active site) of an enzyme. The inhibitor binding to the allosteric site modifies the active site reducing/blocking binding of substrate.
Allosteric inhibitors cannot be outcompeted by adding more substrate concentration. rate of enzyme catalysis unaffected by increasing substrate conc.

Question 18

Enzyme kinetics plot

Answer 18

used to visualize how inhibitors affect enzymes

Question 19

Velocity (V) of reaction

Answer 19

the rate at which a reaction occurs

Question 20

Vmax

Answer 20

the maximum reaction velocity

Question 21

Substrate Concentration (X)

Answer 21

increasing the (X) tends to increase the rate of reaction until enzyme becomes saturated with substrate, reaction rate plateauing

Question 22

Michaelis Constant (KM)

Answer 22

the substrate concentration in which the velocity (V) is 50% of the maximum reaction velocity (Vmax)

Small KM = need a little bit of substrate because enzyme ability/function is still high
Large KM = need many substrates for reaction progression bc enzyme availability/function is low.

Question 23

Enzyme inhibition Vmax and Km : competitive inhibitor vs noncompetitive inhibitor

Answer 23

Competitive inhibitor: Vmax is not changed; Km is increased as it takes a higher substrate conc. to reach Vmax
Non-competitive inhibitor: Vmax is decreased and Km remains the same because increasing conc. of substrate does not reduce this inhibition bc active sites are unavailable