RGI 8 Haemoproteins_II_RD

Respiratory System and Gastrointestinal System Overview

• Focuses on Cooperative Oxygen Binding to Hemoglobin

  • Haemoproteins are proteins containing iron and are crucial for oxygen transport.

Key Topics

Hemoproteins II

• Cooperative oxygen binding to hemoglobin

• Binding of CO2 and H+

• Allosteric effects are crucial for oxygen transport efficiency.

Haemoglobin Structure and Function

Myoglobin and Hemoglobin

• Myoglobin: provides oxygen for respiration in muscle cells.

• Hemoglobin: transports oxygen throughout the body.

  • Composed of 4 subunits: 2 alpha and 2 beta globin chains.

  • Each subunit contains iron (Fe) in its heme group, facilitating oxygen binding.

  • has a proximal histidine to ling the iron haem to globin.

Binding Interactions

• Fe-haem Association

  • Iron is +2 (Fe2+) and is shown to participate in bonding with oxygen.

  • Each iron in hemoglobin can bind to 4 oxygen molecules cooperatively.

  • Changes in iron's electron configuration affect the binding state to O2.

  • Hemoglobin varies between a tense (T) state and a relaxed (R) state based on binding.

Biochemical Mechanisms

Oxygenation and Cooperativity

• Binding of oxygen molecules alters the structure, enhancing further oxygen binding.

• T state (tense): lower affinity for O2.

• R state (relaxed): higher affinity for O2 due to conformational change.

Allosteric Regulation

• Binding of CO2 and H+ ions alters hemoglobin's affinity for oxygen (Bohr Effect).

• Bohr Effect: Increased CO2 and H+ in metabolically active tissues promote O2 release.

Physiological Significance

Transport of CO2 and H+

• Hemoglobin transports CO2 and H+ back to the lungs.

• CO2 is often converted to bicarbonate ( HCO3-) in red blood cells.

• H+ ions bind to amino acid side chains which influence hemoglobin structure.

Impact of pH on Hemoglobin Function

• Decreased pH (increased H+) lowers hemoglobin’s affinity for O2.

• Increased pH increases affinity (right vs. left shift on saturation curves).

Poisonings and Toxins

Carbon Monoxide (CO) Toxicity

• CO binds to hemoglobin with a higher affinity than O2 (225x), leading to impaired oxygen transport.

• Symptoms of CO exposure range from headaches to potential death with high levels.

• Treatment for CO poisoning includes high-pressure oxygen therapy.

  • Risks of long-term exposure to high O2 pressures.

Important Takeaways

• Cooperative binding enhances oxygen transport efficiency.

• Understanding hemoglobin functionality helps elucidate physiological adaptations during respiration.

• Knowledge of CO toxicity underscores the importance of environmental safety measures.

Learning Outcomes

• Interpret oxygen saturation curves for myoglobin and hemoglobin.

• Explain CO2 and H+ transport mechanisms in the blood.

• Define cooperative oxygen binding, allosteric effects, and the Bohr Effect.

• Understand the implications of carbon monoxide toxicity and treatment methods.