Lecture 3

Question 1

where is myoglobin found?

Answer 1

muscle

Question 2

what is the function of myoglobin?

Answer 2

provide reserved supply of O2 and facilitates rapid diffusion of O2 within the muscle

Question 3

how many polypeptide chains does myoglobin contain?

Answer 3

one

Question 4

what is the function of hemoglobin?

Answer 4

O2 carrier in blood

Question 5

how many polypeptide chains does hemoglobin contain?

Answer 5

four

Question 6

what kind of polypeptide chains does hemoglobin contain?

Answer 6

two identical alpha chains and two identical B globin chains

Question 7

do hemoglobin and myoglobin have the same heme group?

Answer 7

yes

Question 8

what are the functional differences between myoglobin and hemoglobin?

Answer 8

Hemoglobin is more complex than myoglobin
-Hb transports H+ and CO2 in addition to O2
- binding of O2 is regulated by H+, CO2 and 2,3BPG

Question 9

how many molecules of O2 can myoglobin bind?

Answer 9

1

Question 10

how many molecules of O2 can hemoglobin bind?

Answer 10

4

Question 11

Is hemoglobin a allosteric protein?

Answer 11

yes

Question 12

is myoglobin a allosteric protein?

Answer 12

no

Question 13

allosteric protein

Answer 13

protein that changes from one conformation to another when it binds to another molecule or covalently modified
- alters the functional activity of protein

Question 13

positive cooperativity

Answer 13

binding of O2 to hemoglobin enhances binding of more O2 to the same hemoglobin

Question 14

what affects the affinity of hemoglobin to O2?

Answer 14

pH and binding of CO2
- also regulated by 2,3BPG

Question 15

which has a higher affinity for oxygen, hemoglobin or myoglobin?

Answer 15

myoglobin, because hemoglobin is regulated by 2,3BPG

Question 16

what are the differences between myoglobin and hemoglobin dissociation curve?

Answer 16

myoglobin is hyperbolic vs hemoglobin is sigmoidal

Question 17

what is the significance of the O2 binding curve of hemoglobin?

Answer 17

hemoglobin is fully saturated with O2 in the lungs (100 torrs) but relreases more than half of its bound O2 in capillaries of active muscles and issues where pO2 is 20torrs

Question 18

what is the significance of cooperatively binding of O2 to hemoglobin?

Answer 18

• communication among the heme groups of Hb
• allows Hb to deliver twice as much as O2 to tissues than if they were to act independantly

Question 19

when are beta chains of hemoglobin closer to one another?

Answer 19

when hemoglobin is in oxygenated form, causing strain on other subunit, causing noncovalent bonds to break

Question 20

what causes changes in hemoglobin quaternary structure?

Answer 20

the movement of Fe atom in heme
- Fe moves into plane (Fe is out of plane when deoxygenated due to steric repulsion)

Question 21

what factors regulate Hb quaternary structure and O2 affinity?

Answer 21

pH, CO2, biding of 2,3 BPG

Question 22

does a low pH or high pH enhance the release of O2 by hemoglobin?

Answer 22

low pH (acidity), shifts dissociation curve to the right, decreasing O2 affinity

Question 23

does pH affect myoglobin affinity of O2?

Answer 23

no

Question 24

what promotes the release of O2 from Hb?

Answer 24

CO2, increasing CO2 lowers affinity of Hb for O2

Question 25

what kind of proteins are used for protein studies?

Answer 25

• utilize crude (not pure) protein preparations
• utilize purified or highly enriched preparations