8.4 enzymes

Question 1

whats an enzyme

Answer 1

a macromolecule that acts as a catalyst

Question 2

whats a catalyst

Answer 2

a chemical agent that speeds up a faction without being consumed by the reaction

Question 3

AB + CD-> AC + BD

Answer 3

spontaneous but first, activation energy needed to break bonds, then new bonds form , releasing energy

Question 4

transition state

Answer 4

the part of the reaction where the reactants are very unstable because their bonds have been broken

Question 5

activation energy (Ea)

Answer 5

the amount of energy needed to push the reaction over the energy barrier so that the energy release part can happen usually supplied by heat

Question 6

what usually is the a activation energy

Answer 6

heat (temperature has to be high enough)

Question 7

what do enzymes do

Answer 7

lower the actuation energy so the faction can happen at room temp.

Question 8

induced fit

Answer 8

when enzymes shape change slightly so that substrate fits even better in it

Question 9

how does temperature affect enzymes

Answer 9

increase and then after a certain point, it sharply decreases (optimal is usually at 35-40ºC) body temp

Question 10

optimal pH of enzymes

Answer 10

6-8 some digestive enzymes in stomach = 2 trypsin=8 ( digestive enzyme in alkaline part of stomach)

Question 11

cofactors

Answer 11

nonprotein helpers for catalytic activity that bind to enzymes

Question 12

organic cofactors

Answer 12

coenzymes

Question 13

why are vitamins important?

Answer 13

they act as coenzymes or raw materials from which coenzymes are made

Question 14

inhibitor

Answer 14

inhibit enzymes

Question 15

irreversible inhibition

Answer 15

if inhibitor bonds covalently to the enzyme -toxins and poisons

Question 16

competitive inhibitors

Answer 16

mimic the substrate and compete for the active site

Question 17

how to counter competitive inhibition

Answer 17

increase substrate so that there are more substrates than inhibitors are present to fill the active site than inihibtors

Question 18

noncompetitive inhibitor

Answer 18

inhibits by binding to another part of enzyme causing molecule to change shape so that it is less effective at catalyzing reactions

Question 19

allosteric enzyme structure

Answer 19

2+ subunits with own -polypeptide chain and active sites

Question 20

how does an allosteric enzyme work

Answer 20

-2 stages -active vs. inactive -in active stage, an activator stabilizes the active form -an inhibitor bind to the allosteric site to stabilize the inactive form

Question 21

ATP feedback

Answer 21

ATP binds to catalytic enzymes allosterically to slow activity -ADP binds to allosteric site as an activator to the same enzymes (b/c if too much ATP is produced there will be more ATP to inhibit and when there is not enough there will be more ADP it activate)

Question 22

cooperativity

Answer 22

when one substrate binds to an active site and has induced fit, all the active sites change to the induced fit -this lets other active sites bind to the substrates faster and easier

Question 23

positive feedback hemoglobin

Answer 23

cooperativity -when one O2 binds, the other sites increase affinity for O2 also in remaining binding sites so -in lungs and like gills, where there is more O2, the hemoglobin binds more

Question 24

allosteric regulators are attractive for enzyme regulation because

Answer 24

they are very specific -active sites can look the same between diff. enzymes but allosteric sites are very specific

Question 25

feedback inhibition

Answer 25

-prevents cell from wasting chemical resources – when too much is made, the product can inhibit the enzyme so that less is made

Question 26

are cells just a bag of chemicals with thousands of different enzymes and substrates randomly

Answer 26

no -its compartmentalized in an arrangement that facilitates sequence of reactions (internal environments)