Bioenergetics & Enzyme Kinetics

Question 1

2nd Law of Thermodynamics

Answer 1

The entropy of the universe is always increasing

Question 2

Sources & Types of High Energy Bonds

Answer 2

Acetyl coA (thioester)
ATP (phosphoanhydride)
Phosphoenolpyruvate (PEP)

Question 3

1st Law of Thermodynamics

Answer 3

The total energy of a system, including its surroundings, remains constant; energy is never created or destroyed but may be transferred or transformed

Question 4

Relationship between free energy, enthalpy, and entropy of a system

Answer 4

dG = dH -TdS

Question 5

Reduction Potential (E)

Answer 5

The more positive the value of E, the more a molecule likes to accepts electrons (become reduced); the more negative the value of E, the more a molecule likes to donate electrons (become oxidized)

As electrons pass from compounds with low (negative) to high (positive) E values, energy is released

Question 6

Relationship between free energy and redox potential

Answer 6

dG = -nFdE

Question 7

Enzyme cofactor

Answer 7

Small molecules (often metal ions) that function within an enzyme to catalyze a reaction; cofactors are not used up in the reaction

Question 8

Coenzyme

Answer 8

Provide chemical groups for a catalyzed reaction and are used up by the reaction

Question 9

Prosthetic Group

Answer 9

A coenzyme or cofactor that is tightly bound to the enzyme

Question 10

Holoenzyme

Answer 10

The intact complex of an enzyme and it’s cofactor/coenzyme

Question 11

Apoprotein

Answer 11

A protein enzyme in isolation, without it’s associated coenzyme/cofactor

Question 12

Equation describing the speed of an enzymatic reaction

Answer 12

Velocity = k[S]

Question 13

Km

Answer 13

Km is the substrate concentration at which Vo = 1/2Vmax

Km typically approximates intracellular concentrations of [S]

Question 14

Kcat

Answer 14

measures the number of substrate molecules turned into product per enzyme molecule, per second

the larger the Kcat value, the faster the enzyme works to turnover

Question 15

1/Kcat

Answer 15

the length of time required for the enzyme molecule to turn one molecule of substrate into product

Question 16

Kcat/Km

Answer 16

A measure of comparing enzyme efficiency; the larger the value, the more efficient the enzyme

Question 17

Catalytic Perfection

Answer 17

Kcat value approaching 10^8 - 10^9 - the enzyme is so efficient that the only limiting factor is the rate of diffusion

Question 18

Competitive Inhibitors

Answer 18

Bind to the enzyme active site and block binding of the natural substrate

Kcat is unaffected, apparent increase in Km as [I] increases

Lineweaver Burke plot lines will intersect at the same y-intercept (at x=0) but have different slopes as [I] changes

Question 19

Uncompetitive Inhibitors

Answer 19

Bind to the ES complex at a site other than the active site

Kcat, Vmax, and Km are affected; Lineweaver Burke plot lines run parallel

Question 20

Mixed Inhibitors

Answer 20

May bind to either E or ES at a site other than the active site

Kcat, Vmax, and Km are changed; Lineweaver-Burke plot lines will intersect (X =/= 0) and have different slopes as [I] changes