lecture 3 - bioenergetics

Question 1

what is the dissociation constant? (Kd)

Answer 1

the reciprocal of the equilibrium constant (Kd = 1/Keq); how tightly a protein binds to its ligand

Question 2

the lower the Kd…

Answer 2

the higher the binding affinity and the tighter the binding of a ligand to its receptor; the lower the ligand concentration needed to reach 50 percent of binding

Question 3

allostery

Answer 3

binding of a molecule at one site on a macromolecule can change the three-dimensional shape of a distant site

Question 4

exergonic

Answer 4

energy-releasing; products contain less energy than the reactants, occurs spontaneously

Question 5

endergonic

Answer 5

energy-absorbing; products contain more energy than the reactants, not spontaneous

Question 6

if delta G is negative…

Answer 6

the forward reaction (formation of products) will occur spontaneously, energy will be released

Question 7

if delta G is positive…

Answer 7

the forward reaction will NOT occur spontaneously, energy must be added

Question 8

if delta G is zero…

Answer 8

both forward and reverse reactions will occur; equilibrium

Question 9

an exothermic reaction in which entropy increases…

Answer 9

occurs spontaneously

Question 10

an endothermic reaction occurs spontaneously if…

Answer 10

entropy increases enough so the term can overcome the positive delta H

Question 11

do enzymes alter the value of delta G?

Answer 11

no; they alter the activation energy

Question 12

what does the velocity at which products are generated depend on?

Answer 12

the concentration of material in the transition state

Question 13

the higher the activation energy…

Answer 13

the lower the fraction of reactants that reach the transition state, and the slower the overall rate of reaction

Question 14

what does lowering the activation energy mean?

Answer 14

decreasing the difference in free energy between the reactants and the transition state

Question 15

what does lowering activation energy result in?

Answer 15

acceleration of overall reaction rate

Question 16

how can endergonic reactions occur spontaneously?

Answer 16

by coupling the reaction with another energy-releasing reaction to result in a negative delta G

Question 17

example of energy-releasing reaction?

Answer 17

hydrolysis of ATP (-7.3 kcal/mol)

Question 18

what type of bond contains useful energy in ATP molecule?

Answer 18

covalent bond; phosphodiester bonds

Question 19

ligand

Answer 19

the molecule to which a protein binds

Question 20

the stronger the interaction between a protein and ligand…

Answer 20

the lower the value of Kd

Question 21

Michaelis-Menten enzyme-substrate-binding hypothesis

Answer 21

the rate of an enzymatic reaction was proportional to the substrate concentration at low substrate concentrations, but at high substrate concentrations, the rate reached a plateau (Vmax)

Question 22

Michaelis constant (Km)

Answer 22

measure of the affinity of an enzyme for its substrate

Question 23

what does the Km indicate?

Answer 23

the substrate concentration that yields a half-maximal reaction rate (1/2Vmax)

Question 24

the smaller the value of Km…

Answer 24

the more effective the enzyme is at making product from smaller concentrations of substrate and the lower the substrate concentration needed to reach half-maximal velocity

Question 25

competitive inhibition

Answer 25

Vmax stays the same, Km increases

Question 26

noncompetitive inhibition

Answer 26

Vmax decreases, Km stays the same

Question 27

3 amino acids that can be phosphorylated

Answer 27

serine, threonine, tyrosine