Biochem Globin Family part 3

:How does pH affect hemoglobin's O₂ binding?

High pH → higher O₂ affinity; Low pH → more O₂ release

Q: Why does hemoglobin release more O₂ in tissues?

Tissues produce CO₂ → increases H⁺ → lowers pH → promotes O₂ release

Q: What happens to P50 when pH decreases?

P50 increases → lower O₂ affinity

Q: What enzyme speeds up CO₂ conversion in RBCs?

Carbonic anhydrase

Q: How does CO₂ indirectly cause O₂ release from hemoglobin?

Produces H⁺ → lowers pH → triggers Bohr effect

Q: What is the role of BPG in hemoglobin function?

Decreases O₂ affinity and promotes O₂ release

Q: Which form of hemoglobin binds BPG most strongly?

Deoxy (T state)

Q: What happens to O₂ binding when BPG is present?

Affinity decreases, more O₂ released

How much O₂ does hemoglobin release from arterial to venous blood?

About 40%

Q: What are typical Hb saturation levels in arterial vs venous blood?

~95% (arterial), ~55% (venous

Why does fetal hemoglobin bind O₂ more tightly than adult hemoglobin?

It binds BPG less strongly

Q: What is the advantage of higher O₂ affinity in fetal Hb?

Allows transfer of O₂ from mother to fetus

Q: What happens when Fe²⁺ is oxidized to Fe³⁺ in hemoglobin?

Forms methemoglobin, which cannot bind O₂

Q: What color change is associated with methemoglobin?

Brown or bluish (cyanosis)

Q: Which amino acid plays a major role in the Bohr effect?

His146β

Q: What stabilizes the T state of hemoglobin?

Salt bridges (e.g., His146β with Asp94β)

Q: What happens when these salt bridges break?

Hemoglobin shifts to the R state

How can mutations affect hemoglobin function?

Change structure, stability, or O₂ binding

Q: What happens if mutations stabilize methemoglobin?

Reduced O₂ transport → cyanosis