Protein Function: Hemoglobin – Key Concepts

22 English vocabulary flashcards summarizing hemoglobin structure, regulation, cooperative binding, disease, and therapeutic strategies.

Hemoglobin

Quaternary structure with 2 a and 2 b chains; has 4 heme groups that can hold 4 O2 molecules; carried by erythrocytes

Myoglobin

Muscle protein with one heme group that can carry one O2 molecule

Heme Prosthetic Group

Porphyrin holding an Fe in the middle, which coordinates 6 bonds (4 to N, 1 to O2)

T (Tense) State

Low O2 affinity conformation of hemoglobin; binding of O2 triggers change to R state

R (Relaxed) State

High O2 affinity conformation of hemoglobin

Cooperative Binding

When one subunit binds to O2, others are likely to bind as well

Sigmoidal Curve

S-shaped binding curve that shows transition from low to high-affinity state

2,3-Bisphosphoglycerate (2,3-BPG)

Neg charged glycolysis intermediate that regulates O2 binding in hemoglobin, which binds to the center of the holocomplex and stabilizes the T state, forcing it to drop O2 at respiring tissues

Bohr Effect

Increased CO2 or decreased pH reduces O2 affinity, enhancing oxygen release

Concerted Model

All-or-none model of cooperativity where entire hemoglobin shifts between T and R states; inadequate alone to explain experimental data.

Sequential Model

Model proposing stepwise subunit transitions upon ligand binding; also insufficient alone, real behavior lies between the two models.

Fetal Hemoglobin (HbF)

hemoglobin with 2 a and 2 gamma; lower affinity for 2,3-BPG and higher O2 affinity

Sickle Cell Disease (SCD)

Homozygous genetic disorder caused by Glu6→Val6 mutation

Hemoglobin S (HbS)

Mutant β-globin tetramer in SCD; deoxygenated form polymerizes, distorting erythrocytes, causing pain and anemia

CRISPR Gene Editing in SCD

Targets BCL11A, increasing HbF expression