Exam 2 - Enzyme Activity

Question 1

Is the active site and the substrate binding site the same?

Answer 1

No

Question 2

What type of inhibition can be reversed by adding substrate?

Answer 2

Competitive Inhibition

Question 3

What are the 3 types of reversible inhibitors?

Answer 3

1. Competitive
2. Uncompetitive
3. Mixed
   
   1. Noncompetitive

Question 4

Competitive inhibitors compete with the substrate for the [] ?

Answer 4

Substrate binding site

Question 6

What rate constant is unchanged in competitive inhibition?

Answer 6

k₃

Question 7

What are the 2 conditions for a noncompetitive inhibitor?

Answer 7

1. k_I and k_I’ have to be identical
2. The Enzyme-substrate-inhibitor cannot make product

Question 8

In noncompetitive inhibition why is the Km lowered?

Answer 8

• Psyche
• The K_m is unchanged in noncompetitive inhibition
• the Vmax is lowered

Question 9

In mixed inhibition, K_I and K_i’ are [] identical…

Answer 9

NOT identical

Question 10

What happens to K_m and V_max with the following types of inhibition?

1. Competitive
2. Mixed
3. Noncompetitive
4. Uncompetitive

Answer 10

1. Vmax is unchanged, Km can change
2. Vmax is lowered, Km can go up or down
3. Vmax is lowered, Km is unchanged
4. Km is lowered, Vmax is lowered

Question 11

Uncompetitive inhibitors bind to the [] complex only, but does not bind to the [] [] [] ….

Answer 11

ES

Substrate Binding Site

Question 12

What is the difference between the active site and the substrate binding site?

Answer 12

• Substrate binding site is the site to where the whole substrate binds to
• Acive site are the specific catalytic residues within the substrate binding site.

Question 13

Allosteric Regulation

• Describes molecules that bind to proteins at some location [] than the substrate binding site - also called the [] site
• Changes [] - positively or negatively
• Targeting []
• Normally small molecules < []

Answer 13

• Other, Allosteric Site
• velocity
• Km
• 3,000 Dal

Question 14

A compound that alters enzyme activity by binding to sites outside of the substrate binding or active sites…

Answer 14

effector

Question 15

What is any molecule that is bound to a macromolecule?

Answer 15

Ligand

Question 16

What is a protomer?

Answer 16

• single subunit in an oligomer
• Usually identical polypeptides

Question 17

Enzymes that undergo [] regulation tend to be control points in metabolic pathways, or the [] [] []?

Answer 17

1. allosteric
2. Rate limiting step

Question 18

Enzymes subjected to allosteric regulation contain an additional binding site called the [] site…

Answer 18

allosteric

Question 19

Homotrophic Interactions involve what?

Are these interactions negative or positive?

Answer 19

• the binding of 1 ligand to protomers affects binding of ligands on other protomers within the same oligomer
• Usually positive interactions

Question 20

What type of activity curve to allosteric enzyes have?

Answer 20

altered sigmoidal curve

Question 21

Heterotrophic interactions involve what?

Are these interactions positive or negative?

Answer 21

• Binding of one ligand affects the binding of a different ligand
• Response can be positive or negative

Question 22

Protein Kinase A is an example of [] regulation

Answer 22

allosteric

Question 23

What enzyme degrades cAMP?

Answer 23

cAMP phosphodiesterase

Question 24

How is a protein kinase activated?

Answer 24

• cAMP interacts with a repressing R group on the catalytic subunit of the protein kinase
• therefore activating the protein kinase.

Question 25

Does cAMP and interact with Protein Kinase A?

Answer 25

* Technically no - it effects the r-group negatively and removes it

Question 26

The first step that is distinct to a biochemical pathway...usually the first irreversible step?

Answer 26

The First Committed Step

Question 27

The reaction within a metabolic pathway that has the highest enery barrier, the slowest reaction...

Answer 27

The Rate Limiting Step

Question 28

What are the 6 mechanism by which enzymes increase the rates of reaction (or decrease the energy of activation)?

Answer 28

1. Acid-Base Catalysis 2. Substrate Strain 3. Covalent Catalysis 4. Transition State Stabilization 5. Entropy effect 6. Ground State destabilization