BSCI330 enzymes

Question 1

what do enzymes do

Answer 1

catalyze chemical reactions and work by stabilizing the reaction’s transition state

Question 2

how are enzymes regulated

Answer 2

by covalent modifications and binding of non-substrate ligands (allosteric regulation)

Question 3

what are enzymes

Answer 3

catalytic proteins - they speed up cellular reactions to allow life and allow you to reach equilibrium faster

Question 4

what can enzymes not do

Answer 4

do not alter delta G

they cannot make a reaction spontaneous if it’s non-spontaneous

cannot change the thermodynamics of a system

cannot alter the concentrations of reactants and products in a reaction mixture that is at equilibrium

won’t let you get more energy per mole of reactant, you just get it faster

Question 5

what is activation energy

Answer 5

the quantity of energy to initiate a reaction

Question 6

what are some qualities for enzymes as catalysts

Answer 6

only required in small amounts

must be left uncharged at the end of a reaction so they can cycle back to bind more substrate

catalyzes equally the forward and reverse reactions

Question 7

how do enzymes begin binding to a substrate

Answer 7

through a stereo-specific active site, forming an enzyme-substrate complex

stereo-specific means they recognize the 3D structure but not the mirror image structures

Question 8

what forms an enzyme-product complex

Answer 8

substrate is chemically converted to product

product is then released and enzyme can bind another molecule of substrate

Question 9

what is Vmax

Answer 9

the rate when enzyme is saturated with substrate

rate = Vmax*[S]/(Km + [S])

Question 10

what is Km

Answer 10

approximately equal to the dissociation constant for the enzyme-substrate complex

low Km = enzyme has a high affinity for its substrate

Question 11

what is required for the series of intermediate steps substrate molecules must pass through

Answer 11

3D geometry of reactants needs to be adjusted for optimal interaction

electrons among reacting atoms must begin to become redistributed

Question 12

what is the transition state for a reaction

Answer 12

an intermediate form between product and reactant with a specific structure

Question 13

how do enzymes function

Answer 13

by stabilizing the transition state which lowers activation energy

Question 14

what are prosthetic groups

Answer 14

non-protein molecules which aid in some protein function

Question 15

what are cofactors/coenzymes

Answer 15

enzyme prosthetic groups

Question 16

what are molecular tunnels

Answer 16

some enzymes perform multiple sub-reactions that must occur at distinct active sites and these structures act as tunnels to direct the intermediate products from one active site to the next

Question 17

what do molecular tunnels do

Answer 17

prevents diffusion of intermediates, prevents decomposition of unstable molecules, and speeds up reaction rates

Question 18

what are multi-enzyme complexes

Answer 18

how enzymes in metabolic pathways are organized to prevent diffusion of products

Question 19

what is feedback control

Answer 19

a product of the pathway regulates one of the earlier enzymes in the pathway (negative feedback is common)

Question 20

what are irreversible inhibitors

Answer 20

when you add the inhibitor, it permanently shuts off the inhibitor

Question 21

what are reversible inhibitors

Answer 21

if inhibitor is there, the protein is off - bind non-covalently to enzyme

Question 22

what is a competitive ibhibitor

Answer 22

reversibly bind to active site and compete with substrate (only one can be in active site at a time)

Question 23

what is a non-competitive inhibitor

Answer 23

reversibly bind away from active site to cause change in enzyme structure that lowers catalytic efficiency

Question 24

what is the difference between competitive and non-competitive inhibitors

Answer 24

competitive:
- once inhibitor is removed, substrate can bind
- increase Km, doesn’t change Vmax
non-competitive:
- doesn’t compete with substrate
- lowers Vmax, doesn’t increase Km or affect substrate binding

Question 25

what is an allosteric regulator

Answer 25

causes shape of enzyme to change

Question 26

what does activating/inhibiting an allosteric molecule mean

Answer 26

activate (promote substrate binding and/or catalysis) or inhibit (prevent substrate binding/catalysis)

Question 27

what is favorable with ATP hydrolysis

Answer 27

ATP -> ADP + Pi = favorable

Question 28

what is unfavorable with ATP hydrolysis

Answer 28

ADP + Pi -> unfavorable

Question 29

what can proteins embedded in cell membranes do

Answer 29

harness the energy to take in nutrients, export waste, and receive and send signals by using ATP/GTP hydrolysis, movement of ions, and transfer of high energy electrons