Chapter 6 - Exam 3

Question 1

Coenzyme

Answer 1

complex organic or metalloorganic molecule that act as transient carriers of specific functional groups

Question 2

Cofactor

Answer 2

1+ inorganic ions (Fe2+, Mg2+, Mn2+, or Zn2+)

Question 3

Prosthetic Group

Answer 3

coenzyme or metal ion that is very tightly or covalently bound to the enzyme protein

Question 4

Holoenzyme

Answer 4

complete catalytically active enzyme together with its bound coenzyme and/or metal ions

Question 5

Apoenzyme

Answer 5

the protein part of a holoenzyme

Question 6

Active Site

Answer 6

the location on the enzyme where the substrates bind

Question 7

Substrate

Answer 7

the molecule that is bound to the active site and acted upon by the enzyme

Question 8

Ground State

Answer 8

the starting point for the reaction

Question 9

Transition State

Answer 9

the point at which decay to substrate or product is equally likely

Question 10

Activation Energy

Answer 10

the difference between the energy at the ground state and the energy at the transition state

Question 11

Keq

Answer 11

equilibrium between S (substrate) and P (product)

Question 12

Change in ΔG during a reaction and how it relates to the function of enzymes.

Answer 12

ΔG: biochemical standard free energy change
-Enzymes lower activation energy (ΔG‡)of a reaction; increasing the rate of the reaction

Question 13

Understand the relationship between delta G and Keq (when one is (–) the other is?)

Answer 13

inverse relationship; one is negative the other is positive

Question 14

Positive Delta G

Answer 14

endergonic reaction (free energy is gained), smaller Keq

Question 15

Negative Delta G

Answer 15

exergonic reaction (free energy is released), larger Keq

Question 16

Higher Keq

Answer 16

reaction tends toward products

Question 17

Lower Keq

Answer 17

reaction tends toward substrates

Question 18

What is the binding energy of an enzyme and how does it relate to the function of the enzyme?

Answer 18

-energy derived from non-covalent enzyme-substrate interaction
-Major source of free energy used by enzymes to lower the activation energy
-The sum of the activation energy and the binding energy results in a lower net activation energy

Question 19

Enzyme Kinetics

Answer 19

the discipline focused on determining the rate of a reaction and how it changes in response to changes in experimental parameters

Question 20

Pre-Steady State

Answer 20

initial transient period during which ES builds up

Question 21

Steady State

Answer 21

period during which ES and other intermediates remain constant

Question 22

Vo, Initial Velocity

Answer 22

tangent to each curve taken at time = 0

Question 23

Vmax

Answer 23

the plateau-like V0 region is close to the Vmax

Question 24

Km (Michaelis-Menten Constant)

Answer 24

-Substrate concentration at which the reaction rate is half of its maximum (Vmax)
-Measurement of the affinity of an enzyme for its substrate

Question 25

What is the relationship between Vmax and Km?

Answer 25

Km is ½ Vmax

Question 26

Competitive Inhibition

Answer 26

-inhibitor competes with the substrate for the active site of an enzyme
-affects Km, but not Vmax

Question 27

Uncompetitive Inhibition

Answer 27

-binds at a site distinct from the substrate active site…binds only to ES complex
-affects Vmax and Km

Question 28

Mixed Inhibition

Answer 28

-binds at a site distinct from the substrate active site; binds to either E or the ES complex
-affects both the Km and the Vmax

Question 29

Noncompetitive Inhibition

Answer 29

-binds at a site distinct from the substrate active site; binds to E or ES complex with equal affinity
-affects only Vmax