Hemoglobin and Myoglobin

Question 1

Hemeprotein

Answer 1

proteins with heme as tightly bound prosthetic group

Question 2

Prosthetic Group

Answer 2

coenzyme permanently associated with enzyme or protein

Question 3

Cytochromes

Answer 3

heme group serves as electron carrier that can be oxidized and reduced
in ETC

Question 4

Catalase

Answer 4

heme is part of active site of enzyme that catalyzes breakdown of hydrogen peroxide
in peroxisomes

Question 5

Heme use in Myoglobin and Hemoglobin

Answer 5

heme used to reversibly bind oxygen

Question 6

Heme Structure

Answer 6

iron in center of porphyrin ring

makes 6 bonds- 4 to iron, 1 to R group of histidine of globin, 1 to oxygen

Question 7

Myoglobin

Answer 7

in heart and skeletal m

O reservoir; carrier that increases transport rate w/in muscle cells

Question 8

Hemoglobin

Answer 8

Red Blood Cells
transports 4 O2 mol from lungs to capillaries of tissues
transports CO2 and H from tissues to lungs

Question 9

T Form

Answer 9

deoxy form when no O bound

low O affinity

Question 10

R Form

Answer 10

O binding causes break of some polar bonds of T form

high O affinity

Question 11

O binding myoglobin vs hemoglobin

Answer 11

1 O to Myoglobin
4 O to Hemoglobin
Myoglobin has higher affinity

Question 12

Bohr Effect

Answer 12

Decreases O affinity at lower pH
shifts curve to right
stabilizes T form

Question 13

2,3 BPG

Answer 13

stabilizes T form
decreases O affinity
shifts curve right

Question 14

CO2 Binding

Answer 14

stabilizes T form
less O affinity
shifts curve right

Question 15

CO Binding

Answer 15

hemoglobin has higher affinity for CO than O; binds more closely
higher O affinity
R form
Shifts curve left

Question 16

Fetal Hemoglobin

HbF

Answer 16

lower affinity for 2,3 BPG (missing some + aa in beta chains of 2,3 BPG)
higher O affinity
shifts curve left
Stabilizes R form

Question 17

What are the proton sources that decrease pH so the Bohr effect can take place?

Answer 17

acids made by tissues (lactic acid)

high levels of CO2 at peripheral tissues (carbonic acids and bicarbonate)

Question 18

pH gradient between lungs and tissues

Answer 18

CO2 releasing carbonic acids and bicarbonate from tissues makes a higher pH in lungs and lower at tissues
hemoglobin becomes more efficient oxygen transporter

Question 19

Mechanism of the Bohr Effect

Answer 19

Deoxyhemoglobin has a higher affinity for protons than oxyhemoglobin (histidine R groups have higher pKa when not O bound)
become protonated = charged R group
charged group form stronger ionic interactions- lower O affininity

Question 20

Where does 2,3-BPG effect take place?

Answer 20

high concentrations of RBC

binds only to deoxyhemoglobin- decreases O affinity

Question 21

Mechanism of 2,3- BPG

Answer 21

binds in pocket between 2 beta globin chains in deoxyhemoglobin
chains contain (+) aa that bind (-) 2,3- BPG
O binding = BPG removed

Question 22

Response of 2,3- BPG to anemia/ chronic hypoxia

Answer 22

2,3-BPG levels rise

increases ability to unload O in tissues

Question 23

Role of 2,3- BPG in transfused blood

Answer 23

needed for normal transport
w/o O can not be unloaded efficiently
BPG lost when blood is stored; O binds too tightly in transfused patients until BPG levels return to normal

Question 24

Transporting forms of CO2

Answer 24

Normal- bicarbonate ion

Or- carbamate bound to N terminal aa of hemoglobin which forms carbaminohemoglobin

Question 25

Where does CO2 dissociate from hemoglobin?

Answer 25

Lungs

Question 26

Affect of CO binding to hemoglobin

Answer 26

tight binding (200x higher affinity)
No O can unload at peripheral tissues

Question 27

Effects of fetal hemoglobin

Answer 27

higher O affinity

able to absorb O from maternal circulation across placenta

Question 28

Hemoglobin A2

Answer 28

minor hemoglobin with unknown function

Question 29

Sickle Cell Anemia

Hemoglobin S disease

Answer 29

Glutamate replaced by valine (more +)
RBC lifespan about 20 days
T form stiffens and distorts cell
can interrupt flow through capillaries- anoxia- can kill tissue

Question 30

Hemoglobin C Disease

Answer 30

Lysine substituted for glutamate

homozygotes have mild chronic hemolytic anemia

Question 31

Hemoglobin SC Disease

Answer 31

genetics- 1 HbS and 1 HbC

some sickling and crises