focus chapter 6 (enzymes)

Question 1

general properties of enzymes

Answer 1

o Biological catalysts
o Accelerate chemical reactions under physiological (mild) conditions
o Most are proteins
o Highly specific in their reaction and substrate
o Capacity for regulation
o Not changed or used up after a reaction

Question 2

Oxidoreductases

Answer 2

 Can catalyze oxidation/reduction reactions
 Transfer electrons from one substance to another

Question 3

Transferases

Answer 3

Transfer a functional group from one substance to another

Question 4

Hydrolases

Answer 4

Help form two products through hydrolysis

Question 5

Lyases

Answer 5

Non-hydrolytic addition or removal of groups from substrate

Question 6

Isomerases

Answer 6

Intramolecule rearrangement (isomerization)

Question 7

Ligases

Answer 7

New bonds with simultaneous breakdown of ATP

Question 8

Translocases

Answer 8

Catalyze the movement of ions or molecules across membranes of their separation within membranes

Question 9

Exergonic reactions have a

Answer 9

negative ΔG (free energy is released)…favorable

Question 10

are endergonic or exergonic reactions favorable

Answer 10

exergonic

Question 11

Endergonic reactions have a

Answer 11

positive ΔG (free energy input required)…unfavorable

Question 12

A reaction is spontaneous if

Answer 12

 change in G is less than 0
 enzymes do not affect change in G

Question 13

Thermodynamics

Answer 13

looks at standard free energy and tells you if the reaction will happen

Question 14

kinetics

Answer 14

 How fast a reaction is happening
 Is effected by enzymes

Question 15

energy diagrams of enzyme catalyzed reactions

Answer 15

o X-axis is reaction progress
 Time value
o Y-axis is free energy
 It tells you if the reaction is exergonic or endergonic
o The difference in heigh from the substrates and the products is the change in G for the reaction
o Catalyzed before transition state and uncatalyzed after

Question 16

transition state

Answer 16

A molecular form that is no longer substrate but not yet product

Question 17

Enzymes facilitate the formation of

Answer 17

the transition state

Question 18

Activation energy

Answer 18

the energy required to form the transition state from the substrate

Question 19

Relate chemical kinetics to an understanding of how enzymes increase reaction rates

Answer 19

o Enzymes do not change the equilibrium of a reaction
o Enzymes decrease the activation energy, accelerating the reaction
o Enzymes decrease the time to reach the equilibrium

Question 20

Lock and key model

Answer 20

Substrate must perfectly fit the enzyme

Question 21

The induced fit model

Answer 21

When the substrate fits together with the enzyme, the enzyme itself will change to either join substrates together or break a substrate down

Question 22

the two main models describing enzyme-substrate interactions

Answer 22

lock and key model and the induced fit model

Question 23

key characteristics of enzyme active sites

Answer 23

o The active site is a three-dimensional cleft or crevice created by amino acids from different parts of the primary structure.
o The active site constitutes a small portion of the enzyme volume.
o Active sites create unique microenvironments.
o The interaction of the enzyme and substrate at the active site involves multiple weak interactions.
o Enzyme specificity depends on the molecular architecture at the active site.

Question 24

Explain the relationship between the transition state and the active site of an enzyme.

Answer 24

o Transition states are unstable arrangement of atoms that cannot be isolated.
o Transition state analogs mimics this arrangement, inhibiting the enzyme.
o Enzymes prefer to bind the transition state, because it represents the highest energy with the best binding.