Enzymes

Question 1

Why are enzymes better than chemical catalysts?

Answer 1

extremaly efficient, more specific (can tell difference between L and D), operate at phsyiological pH and temperature

Question 2

What do some enzymes require to work?

Answer 2

cofactors or coenzymes

Question 3

What is an apoenzyme? Holoenzyme?

Answer 3

enzyme that is missing something so it can’t work

has everything it needs to work

Question 4

What is Vmax?

Answer 4

constant which is the max veloctiy enzyme can work (fixed enzyme conc)

Question 5

What does k1 describe?

What order is this rate constant?

Answer 5

the reaction rate for how quickly E and S can combine, depends on this as well as how much S there is

2nd

Question 6

What does k-1 describe?

What order is this rate constant?

Answer 6

the reaction rate for how quickly ES can dissociate into E and S

1st

Question 7

What is the slowest step in enzymatic reaction?

Answer 7

k2, breakdown from ES to E + P

Question 8

What is Km? What is the unit?

Answer 8

michealis constant, describes the relationship between substrate conc. and reaction rate

M

Question 9

How can you calculate Km?

Answer 9

=(k-1+k2)/k1

Question 10

When does Km equal substrate concentration?

Answer 10

when Vo is 1/2 Vmax

Question 11

What is Vo?

Answer 11

initial velocity

Question 12

What is kcat?

Answer 12

first-order rate constant that determines the reaction rate when the enzyme is fully occupied at a saturating concentration of the substrate

Question 13

What is the specificity constant?

Answer 13

kcat/Km

describes real total efficiency of an enzyme (s^-1 M^-1)

Question 14

What are two ways to get faster efficiency?

Answer 14

really big numerator or really small denominator (kcat/Km)

Question 15

What is the equation of lineweaver-burk plot?

Answer 15

1/Vo=(Km/Vmax)(1/[S]) + 1/Vmax

Question 16

Using a lineweaver-burk, Vmax is 0.02 sec/mol, x-int is -2.5mM^-1, what is Km?

Answer 16

0.4mM (xint equals -1/Km so (-1/-2.5)

Question 17

What does x-int of lineweaver-burk plot equal?

Answer 17

-1/Km

Question 18

What factors affect enzyme activity?

Answer 18

substrate concentration, temperature, pH

Question 19

What are some features of the active sites of enzymes?

Answer 19

shape mimics substrate, small compared to rest of enzyme, substarets are held in by waek covalnet bonds

Question 20

What are the types of enzyme inhibition?

Answer 20

competitive, uncompetitive, mixed competitive

Question 21

What is competitive inhibtion? What does it impact?

Answer 21

competes for active site with substrate

changes the Km

Question 22

How does competitive inhibition change michaelis-menton equation?

Answer 22

a is added to equation

Vo=Vmax[S]/(aKm+[S])

where a=1+[I]/Ki and Ki=[E][I]/[EI]

Question 23

How does competitive inhibition change lineweaver-burk plot?

Answer 23

change the slope and x-intercept

Question 24

What is uncompetitive inhibtion? What does it impact?

Answer 24

binds away from active site and strains enzyme

reduces efficinecy

Question 25

How does uncompetitive inhibition change michaelis-menton equation?

Answer 25

a’ is added

Vo=Vmax[S]/(Km+a’[S])

Question 26

How does an uncompetitive inhibitor affect Vo?

Answer 26

at low [S] Vo=Vo

at high [S] apparent Vo<Vo

Question 27

How does uncompetitive inhibition change lineweaver-burk plot?

Answer 27

changes x and y intercept

Question 28

What is mixed competitve (noncompetitive) inhibtion?

Answer 28

inhibitor may bind to the enzyme whether or not the enzyme has already bound the substrate

Question 29

How does mixed competitive inhibition change michaelis-menton equation?

Answer 29

Vo=Vmax[S]/aKm+a’[S]

Question 30

How does mixed competitive inhibition change lineweaver-burk plot?

Answer 30

point where the lines intersect is not on y axis

vmax is changed

Question 31

What is irreversible inhibition?

Answer 31

inhibitor makes an irreversible covalent bond in the active site of the
enzyme, locking it in an inactive
conformation

Question 32

WHat kind of inhibition lowers Vmax and Km by the same degree?

Answer 32

uncompetitive