Hemoglobin

Question 1

Hemoglobin

Answer 1

Tetramer of polypetides (globins) which each contain a heme group

Question 2

In adults, what type of globin chains are the tetramers comprised of?

Answer 2

2 alpha and 2 beta

Question 3

Which amino acid is responsible for holding the heme group in place and is on the inside of the globin?

Answer 3

Histidine

Question 4

Myoglobin

Answer 4

Oxygen storing molecule found in skeletal and cardiac muscle
A monomer

Question 5

Which globin is more suited for storage and which is more suited for delivery?

Answer 5

Myo - storage

Hemo - delivery

Question 6

p50

Answer 6

The partial pressure at which Hb is 50% saturated

Question 7

What does the binding affinity curve look like for hemeoglobin?

Answer 7

Sigmoidal

Question 8

What does the binding affinity curve for myoglobin look like?

Answer 8

Hyperbolic

Question 9

Because of it’s monomer nature and binding affinity what must occur for myoglobin to give up its oxygen?

Answer 9

The environment must be heavily lacking in oxygen

Question 10

Because of it’s quaternary structure, Hb participates in;

Answer 10

Cooperative binding

Question 11

Where does Mb release its oxygen to?

Answer 11

Cytochrome oxidase to be used in the electron transport chain to fuel muscle contraction

Question 12

In deoxyHb Fe is out of place with the heme. How does it go back into the correct plane?

Answer 12

Binding of oxygen sources

Question 13

What are the two states each component of the Hb tetramer can exist in?

Answer 13

Tense or relaxed

Question 14

How can an Hb tetramer component be in different states?

Answer 14

Due to salt bridges

It take more energy to bind to the first Hb because the salt bridges must be broken

Question 15

Embryonic globins have what type of globin subunits?

Answer 15

Epsilon and zeta

Question 16

Fetal globin has what type of globin structure?

Answer 16

Gamma

Question 17

When is gamma globin completely replaced?

Answer 17

At birth

Question 18

Which has a higher affinity for O2, fetal or adult Hb and why?

Answer 18

Fetal so that it can obtain as much oxygen from the mother’s blood without too much competition

Question 19

What lowers the the O2 affinity of Hb?

Answer 19

2,3-BPG

by associating in the pocket formed by the Hb tet

Question 20

What does 2,3-BPG do to lower O2 affinity?

Answer 20

Stabilizes the T-structure of Hb
Forms salt bridges
Low pO2 triggers more 2,3-BPG to be formed in Rapoport-Luberin shunt

Question 21

What is the problem with banked blood?

Answer 21

2,3-BPG levels tend to fall decreasing the ability to release oxygen into tissues

Question 22

Which is more soluble in blood? O2 or CO2?

Answer 22

CO2

Question 23

How does CO2 become H2CO3?

Answer 23

When it diffuses into RBCs it become hydrated by carbonic anhydrase

Question 24

Haldane effect

Answer 24

Describes how an inc in Hb-O2 binding dec the amount of proton binding

Question 25

Bohr effect

Answer 25

How Hb binding to O2 is effected by pH

As CO2 levels rise, deoxyHb will bind to proteins much more readily than it will bind to O2

Question 26

If the p50 exists in a high pH what occurs?

Answer 26

Hb is more prone to give up its oxygen in venous blood

Question 27

What is the chloride/bicarb exchanger which moves HCO3-?

Answer 27

Band 3

Question 28

For every HCO3- moved out of the cell, what moves into the cell and what is it called?

Answer 28

Cl-, chloride shift

Question 29

Thalassemias

Answer 29

Describe when the ratio of alpha to beta globin subunits is not 1:1

Question 30

Sickle cell

Answer 30

Describes a specific globin allele (Hbs) which results from a single nucleotide substitution and leads to the formation of fiberous polymers of Hb

Question 31

Alpha-Thalassemia

Answer 31

A group of genetic disorders leading to altered levels of the alpha globin subunit

Question 32

Beta-Thalassemia

Answer 32

Extremely heterogeneous group of genetic disorders resulting in changes in amount of beta-globin synthesis
Pts with higher HbF tend to do better

Question 33

Sickle cell

Answer 33

Caused by single nucleotide substitution of beta-globin gene resulting in Glu-Val sub
Val causes a sticky patch