Protein Function

Question 1

Which protein that we studied is a monomer?

Answer 1

Myoglobin

Question 2

Which protein that we studied is a oligomer?

Answer 2

Hemoglobin

Question 3

What is the major function of hemoglobin?

Answer 3

Binds to oxygen in the lungs and releases it in the tissues.

Question 4

What is the major function of myoglobin?

Answer 4

Binds oxygen in muscle

Question 5

What ability of proteins does the function heavily depend on?

Answer 5

Ability to bind to other small molecules REVERSIBLY

Question 6

The ______ the affinity of Y for X the more XY we will have at any [] of X or Y.

Answer 6

Greater

Question 7

What is Kd?

Answer 7

The concentration of ligand that gives 50% binding.

Question 8

A small Kd =

Answer 8

high affinity

Question 9

The structure of myoglobin is…

Answer 9

153 amino acids, 8 alpha helices + loops and a heme prosthetic group.

Question 10

Where does heme fit perfectly in myoglobin?

Answer 10

Hydrophobic pocket between E and F.

Question 11

Heme is…

Answer 11

circular and planar

Question 12

Fe2+ in heme can form how many coordination bonds?

Answer 12

6

Question 13

How is the porphyrin ring in heme held in place?

Answer 13

Hydrophobic interactions and coordination bond between Fe2+ and HisF8.

Question 14

What is the main function of HisF8 (proximal)?

Answer 14

Permanently attach heme to global.

Question 15

Where does oxygen bing to the heme group in myoglobin?

Answer 15

the 6th coordination position.

Question 16

Oxygen always bonds at an angle, true of false?

Answer 16

True

Question 17

Which His helps prevent oxidation of Fe2+?

Answer 17

HisE7 (distal)

Question 18

Binding sites are designed precisely to optimize binding…

Answer 18

Specificity and affinity

Question 19

Which His allows specificity for oxygen binding at the heme?

Answer 19

HisE7

Question 20

Myoglobin has a _____ plot.

Answer 20

Hyperbolic

Question 21

Does myoglobin have quaternary structure?

Answer 21

No, only tertiary.

Question 22

How many subunits does hemoglobin have?

Answer 22

4

Question 23

How many O2 can Hb bind?

Answer 23

4

Question 24

Define conservative substitutions.

Answer 24

Minor effects on structure

Question 25

Define critical substitutions.

Answer 25

Can change structure and therefore function

Question 26

Hyperbolic curve is indicative of…

Answer 26

constant affinity

Question 27

Sigmoidal curve is indicative of…

Answer 27

cooperative binding affinity

Question 28

Hemoglobin has a _________ plot.

Answer 28

Sigmoidal

Question 29

Sigmoidal oxygen binding curve means…

Answer 29

Cooperative process, necessary for efficient O2 delivery, reflects a change in binding affinity

Question 30

How does Hb change its affinity for oxygen?

Answer 30

Conformational change

Question 31

What are the two states of Hb?

Answer 31

Tense (low affinity, more salt bridges) and relaxed (high affinity, less salt bridges)

Question 32

What is allostery?

Answer 32

The binding of a ligand at one site on a protein affects the binding of ligands at other sites.

Question 33

What is homoallosteric?

Answer 33

Binding of the effector affects further binding of the SAME compound

Question 34

What is heterosteric?

Answer 34

Binding of the effect affects further binding of a DIFFERENT compound

Question 35

Oxygen is a _______ activator of Hb.

Answer 35

homoallosteric