Chapter 8 Mechanisms and inhibitors

Question 1

What is Covalent catalysis?

Answer 1

The active site contains a reactive group, usually a nucleophile that is briefly covalently modified.

Question 2

What is nucleophile?

Answer 2

its something that has a negative charge seeking positive charge

Question 3

What is general acid-base catalysis

Answer 3

A molecule other than water donates or accepts a proton.

Question 4

What is metal ion catalysis ?

Answer 4

Metal ions function in a number of ways including serving as an electrophilic catalyst.

Question 5

What is Catalysis by approximation and orientation?

Answer 5

The enzyme brings two substrates together in an orientation that facilitates catalysis

Question 6

What is an electrophile

Answer 6

A chemical that is electron deficient

Question 7

How is the rate of an enzyme- catalyzed reaction affected by increasing temperature and what happens if the temperature is too high

Answer 7

It helps to enhance the rate but if it is too high it will also break the structure

Question 8

Most enzymes have an __________ pH

Answer 8

optimal (So this means that at a certain pH the enzyme will perform better)

Question 9

What is Competitive inhibition ?

Answer 9

The inhibitor is structurally similar to the substrate and can bind to the active site, preventing the actual substrate from binding

Question 10

What is uncompetitive inhibition?

Answer 10

The inhibitor binds only to the enzyme-substrate complex. (it can only bind when the enzyme is bonded to the substrate) THIS ONE BINDS TO THE BINDING SITE

Question 11

What is Noncompetitive inhibition?

Answer 11

The inhibitor binds either the enzyme or enzyme-substrate complex (this one binds regardless if the enzyme and substrate are bonded or not) THIS ONE BINDS TO THE ALLOSTERIC SITE ALSO KNOWN AS THE NON BINDING SITE

Question 12

In competitive inhibition does the Vmax change ? Why or why not?

Answer 12

It is unchanged, because the inhibition can be overcome by a sufficiently high concentration of a substrate

Question 13

What happens to the Km value in competitive inhibition?

Answer 13

IT increases in the presence of an inhibitor

Question 14

What happens to the Vmax in uncompetitive inhibition?

Answer 14

-It is lower in the presence of inhibitor
- In this case you cant overcome the inhibition by the addition of excess substrate as it isn’t competing for the same spot.

Question 15

What happens to the Km in uncompetitive inhibitions? is it higher or lower?

Answer 15

Lower

Question 16

What does the competitive inhibition double reciprocal plot look like?

Answer 16

The lines will intersect on the y axis and the 1/Km will move closer to 0 and more steep if the inhibition is present

Question 17

What does the uncompetitive inhibition double reciprocal plot look like?

Answer 17

the two lines are just parallel to each other

Question 18

What does the noncompetitive double reciprocal plot look like?

Answer 18

The two lines intersect on the negative side of the x axis.

Question 19

Irreversible inhibitors bind _______________ to enzymes

Answer 19

Very tightly

Question 20

What do the group specific reagents react with?

Answer 20

R groups of specific amino acids. but only if the amino acid is exposed on the surface

Question 21

How do affinity labels and substrate analogs inhibit the enzyme

Answer 21

They are structurally similar to the enzymes substrate but inhibit by covalently modifying an amino acid in the active site

Question 22

How do the suicide inhibitors or mechanism based inhibitors inhibit the enzyme?

Answer 22

They bind to the enzyme as a substrate and as catalysis occurs the enzyme modifies the substrate converting it into ab irreversible inhibitor.
The enzyme basically kills itself in this one

Question 23

What kind of enzyme is a chymotrypsin and what is it secreted by ?

Answer 23

it is a proteolytic enzyme and it is secreted by pancreas

Question 24

What does a chymotrypsin enzyme do?

Answer 24

It hydrolyzes peptide bonds selectively on the carboxyl side of large hydrophobic amino acids.

Question 25

What two steps does the Chymotrypsin proceed in >

Answer 25

• The rapid formation of an acyl-enzyme intermediate then a slower release of the acyl component to regenerate the free enzyme

Question 26

HIstidine removes a __________from serine____,generating a ________________________

Answer 26

proton,195,Highly reactive alkoxide ion

Question 27

_____________orients the histidine and renders it a better _____________

Answer 27

Aspartate, proton acceptor

Question 28

Where is the oxyanion hole located?

Answer 28

In the region of the active site and it stabilizes the tetrahedral reaction intermediate