Hemoglobin and Myoglobin

Question 1

[1]:
circulating form
binds oxygen at high pH
release oxygen at low pH
carries CO2 and H+ back to lungs
[2]:
facilitates oxygen diffusion and storage in tissues
binds oxygen tighter
pH change does not affect its affinity

Answer 1

[1] Hemoglobin (Hb)

[2] Myoglobin (Mb)

Question 2

Heme Structure:

Heme = [1] + [2]

Answer 2

[1] Protoporphyrin IX (9) Ring

[2] Fe(2+)

Question 3

Hemoglobin:
4 of the iron attachments are to nitrogen
1 is to [1]
the other is to [2]

Answer 3

[1] oxygen

[2] histidine residue

Question 4

The equilibrium dissociation constant (Kd) is the concentration of ligand at which [1].
The more tightly a protein binds to a ligand, the [2] its Kd value will be.

Answer 4

[1] half of the available ligand binding sites are occupied
[2] lower
– need less because affinity high

Question 5

The [1] value is the concentration of the ligand (partial pressure of oxygen) at which 50% of the myoglobin binding sites are occupied.
This binding curve has a [2] shape.

Answer 5

[1] p50
– Kd // partial pressure of oxygen
[2] hyperbolic

Question 6

Hemoglobin has a [1] Kd compared to myoglobin.

Answer 6

[1] higher

– hemoglobin has a lower affinity for oxygen

Question 7

A binding affinity curve shift to the right indicates [1].

Answer 7

[1] weaker affinity/binding

Question 8

The [1] state is the lower binding affinity state of hemoglobin when no oxygen is attached. The [2] state is the higher binding affinity state of hemoglobin when oxygen is attached.

Answer 8

[1] T State (tense)

[2] R State (relaxed)

Question 9

The T(tense) state of the hemoglobin (out of phase and stable) is driven by [1].

Answer 9

[1] ionic interactions (salt bridges)

Question 10

Oxygen will increase binding affinity to hemoglobin under these conditions:
- increased concentration of [1] and/or [2]

Answer 10

[1] oxygen (O2)

[2] carbon monoxide (CO)

Question 11

Oxygen will decrease binding affinity to hemoglobin under these conditions:

• increased concentration of [1], [2], and/or [3]
• oxidation of iron in Hb from [4]

Answer 11

[1] H+ (lower pH // acidic)
[2] carbon dioxide (CO2)
[3] 2,3-bisphosphoglycerate (BPG)
[4] 2+ –> 3+ (methemoglobin)

Question 12

[1] Effect:

Hemoglobin oxygen binding affinity is [2] related both to acidity and to the concentration of carbon dioxide

Answer 12

[1] Bohr

[2] inversely

Question 13

[1] is hemoglobin with carbon dioxide directly bound to it.

Answer 13

[1] carbaminohemoglobin

Question 14

Carbon dioxide is most readily transported in the blood as [1]. This is catalyzed by the enzyme [2] and explains the drop in acidity associated with carbon dioxide.

Answer 14

[1] bicarbonate and H+
– carbonic acid is the intermediate
[2] carbonic anhydrase

Question 15

[1] has an EXTREMELY high affinity for hemoglobin compared to oxygen.
This molecule stabilizes the R state.
You can pick up oxygen and you can’t unload it as easily. Very not good.

Answer 15

[1] Carbon Monoxide (CO)

Question 16

[1] Syndrome
Infants are susceptible to nitrates ingested in drinking water
exposure to exogenous oxidizing agents
can be from well water
methemoglobinemia
can also be due to defective enzyme that reduces iron

Answer 16

[1] Blue Baby Syndrome

– red blood turns more blue … less oxygen … oxidized iron

Question 17

[1] is a compensatory molecule that allows our bodies to deliver a higher percentage of oxygen to our tissues at higher altitudes.

Answer 17

[1] 2,3-BPG

– lowers affinity; shifts curve to the right

Question 18

Fetal hemoglobin has a lower affinity for [1] than human hemoglobin due to the presence of [2]. That means babies have a corresponding higher affinity for oxygen binding than adult hemoglobin.

Answer 18

[1] BPG

[2] two gamma chains (replace BETA chains; serine replaces histidine in BPG binding pocket)