What are globular proteins?
Compact, spherical, water-soluble proteins with dynamic roles (enzymes, transport, regulatory molecules).
What is heme?
A prosthetic group made of protoporphyrin IX + Fe²⁺ that binds oxygen.
Describe heme structure.
Four pyrrole rings forming a porphyrin ring with central ferrous iron (Fe²⁺).
Structure of myoglobin?
Single polypeptide chain + one heme group.
Function of myoglobin?
Oxygen storage in muscle. Releases O₂ only at very low O₂ levels.
Location of myoglobin?
Skeletal muscle + cardiac muscle.
Why does myoglobin have high oxygen affinity?
Single O₂-binding site → non-cooperative hyperbolic binding curve.
Structure of hemoglobin?
Tetramer: 2 α + 2 β subunits, each with a heme group (4 O₂ binding sites).
Function of hemoglobin?
Transport O₂ from lungs → tissues; transport CO₂ from tissues → lungs.
Why does Hb show a sigmoidal curve?
Subunit interactions → cooperative binding.
How do structural differences between Mb and Hb affect oxygen binding?
- Mb: single chain → high affinity, no cooperativity → O₂ storage * Hb: tetramer → variable affinity, cooperativity → O₂ transport
What happens when O₂ binds heme Fe²⁺?
Iron moves into porphyrin plane → triggers conformational change.
How does oxygen bind to myoglobin?
Single direct binding → hyperbolic curve.
How does oxygen bind to hemoglobin?
Stepwise → each O₂ increases affinity (cooperative).
What is cooperative binding?
Binding of one O₂ increases affinity at remaining sites.
What is the T-state?
“Tense” state — low O₂ affinity; stabilized by CO₂, H⁺, 2,3-BPG.
What is the R-state?
“Relaxed” state — high O₂ affinity; stabilized when O₂ binds.
How does O₂ binding convert T → R?
Fe²⁺ movement breaks salt bridges, increasing affinity.
Describe Mb O₂ curve.
Hyperbolic — always high affinity.
Describe Hb O₂ curve.
Sigmoidal — low affinity at low pO₂, high affinity at high pO₂.
What does a right shift mean?
Decreased affinity → more O₂ delivered to tissues.
What does a left shift mean?
Increased affinity → less O₂ released to tissues.
What factors decrease Hb affinity (right shift)?
↑ CO₂, ↑ H⁺ (↓ pH), ↑ temperature, ↑ 2,3-BPG.
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Week 1- Water, Buffers43
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Amino Acids45
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Fibrous Proteins38
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Quick Ones For Fibrous Proteins23
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Quickies For Protein Structure28
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Quickies For Week 429
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Quickies For Enzymes32
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Week 441
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Week 623
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Week 331
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Week 1019
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Week 1219
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Week 1343
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Week 13 P245
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Week 1426
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Week 1522
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Week 1213
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Week 958
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Week 1055
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Week 1145
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Week 1255
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Week 1452
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Week 1546
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Week 1665
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Week 940
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Week 1116
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Week 1330
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Week 1621
