Structure and Function of Hb

Question 1

What shape does a hemoglobin molecule have

Answer 1

Tetrametric shape

Question 2

What are the 4 types of hemoglobin

Answer 2

Adult Hb (HbA)

Fetal Hb (HbF)

HbA2

HbA1C

Question 3

Which hemoglobin has 2 α and 2 β-chains

Answer 3

Adult Hb and HbA1C

Question 4

Which hemoglobin has 2α and 2γ chains

Answer 4

Fetal Hb

Question 5

Which hemoglobin has 2α and 2δ chains

Answer 5

Adult HbA2

Question 6

What is another name for HbA1C

Answer 6

Glycated Hb

Question 7

genes for beta chains are found on which chromosome

Answer 7

chromosome 11

Question 8

genes for alpha chains are found on which chromosome

Answer 8

chromosome 16

Question 9

which fetal site of globin synthesis is 12 weeks till birth

Answer 9

spleen

Question 10

beta globins are missing from hemoglobin due to low transcription. which part of the gene is probably defected

Answer 10

locus control region

Question 11

what type of porphyrin ring does Hb contain

Answer 11

protoporphyrin IX

Question 12

Which form of iron contained in heme allows it to bind to oxygen

Answer 12

ferrous oxide (Fe2+)

Question 13

A large amount of ferric oxide in Hb can indicate which pathological condition

Answer 13

Methemoglobinemia

Question 14

What is the clinical presentation for a deficiency of NADH-metHb and what is the condition called

Answer 14

Cyanosis

Methemoglobinemia

Question 15

drugs containing which suppose can lead to acquired methemoglobinemia

Answer 15

Nitrates

Question 16

ferrous oxide is held in the center of the porphyrin rings of heme by which molecules

Answer 16

nirtogen

Question 17

which globin chain has more alpha helical segments (alpha or beta)

Answer 17

beta

Question 18

the proximal histidine around heme binds to _____ while the distal histidine stabilizes ____

Answer 18

Fe2+

O2

Question 19

Which form of Hb is more abundant in the tissues? Why is this?

Answer 19

T-form because it has less affinity for O2 so O2 can be off loaded easier to tissues that need it

Question 20

Which form of Hb is more abundant in the lungs? Why is this?

Answer 20

R-form because it has a higher affinity for O2 and in the lungs the RBCs there need to hold on to the O2 they just received from the alveolar air

Question 21

myoglobin is mainly found in which tissues

Answer 21

Heart and skeletal muscles

Question 22

Pertaining to the structure of myoglobin why does it make sense that it’s dissociation curve is hyperbolic

Answer 22

it is monomeric, with only one heme group so it just accepts O2 until it;s saturated

Question 23

Pertaining to the structure of myoglobin why does it make sense that it’s dissociation curve is sigmoidal

Answer 23

it is tetrameric, so the one O2 binds which increases the affinity for more O2 so the slope of the curve increases as the consecutive sites get filled until they are all filled

Question 24

in which type of hemoglobin does the alpha globin chain have 8 alpha helical segments

Answer 24

myoglobin

Question 25

Which four factors can influence loading and unloading of O2 in Hb

Answer 25

pH
partial pressure CO2
partial pressure of O2
2,3-bisphosphoglycerate

Question 26

a defect in the second half of glycolysis could potentially affect oxygen dissociation in Hb why?

Answer 26

in glycolysis, 1,3-bisphosphoglycerate is made which is used to make 2,3-bisphosphoglycerate which aids in oxygen dissociation

Question 27

What factors affecting O2 dissociation would cause the a right shift in the O2 dissociation curve

What does a right shift indicate

Answer 27

decreased CO2
high pH
high 2,3-bisphosphoglycerate

A right shift indicates more release of O2

Question 28

What factors affecting O2 dissociation would cause the a left shift in the O2 dissociation curve

What does a left shift indicate

Answer 28

increased CO2
low pH
low 2,3-bisphosphoglycerate

A left shift indicates less release of O2

Question 29

A right shifted O2 dissociation curve more resembles which form of Hb

Why is this?

Answer 29

T-form

Because in the T-form, Hb has less affinity for O2 so there is more release of O2

Question 30

A left shifted O2 dissociation curve more resembles which form of Hb

Why is this?

Answer 30

R-form

Because in the R-form, Hb has more affinity for O2 so there is less release of O2

Question 31

Elevated 2,3-bisphosphoglycerate is seen in which conditions

Answer 31

Hypoxia (high altitude) and chronic anemia

Question 32

Does 2,3-bisphosphoglycerate bind to alpha or beta chains

Answer 32

beta chain

Question 33

Absence of what in HbF make them bind poorly to 2,3-bisphosphoglycerate

Answer 33

beta globin chain

Question 34

Why does HbF need to have high affinity for O2

Answer 34

to trap maternal O2 for the fetus

Question 35

What are the 4 main hemoglobinopathies

Answer 35

sickle cell anemia (HbS)
hemoglobin C
hemoglobin SC
thalassemia

Question 36

What is the defect in sickle cell anemia (HbS)

Answer 36

change of glutamic acid to valine in the 6th postion of the beta chain

Question 37

What is the defect in HbC

Answer 37

change of glutamic acid to lysine in the 6th postion of the beta chain

Question 38

Thalassemia is due to what

Answer 38

decreased Hb

Question 39

Methylene blue can be used to treat a condition with a deficiency in which enzyme?

What is the condition?

Answer 39

Deficiency in NADH-metHb reductase

Methemoglobinemia

Question 40

Carboxy hemoglobin causes Hb to be predominantly in which form? this leads to?

Answer 40

R-type

Less O2 dissociation (hypoxia)