resp 3 Flashcards
How does hemoglobin increase the oxygen-carrying capacity of blood?
It chemically binds 98.5% of oxygen, allowing blood to transport much more O₂ than plasma alone could.
Describe the structure of a hemoglobin molecule and its functional components.
Hemoglobin has four globin subunits (2α and 2β), each with a heme group that binds O₂ and globin chains that bind CO₂, H⁺, and phosphates.
What happens to hemoglobin at high PO2 levels in the lungs?
It becomes ~98% saturated with oxygen, forming oxyhemoglobin.
What promotes oxygen release from hemoglobin in tissues?
Lower PO₂ in tissues encourages hemoglobin to release oxygen, forming deoxyhemoglobin.
What does the oxygen equilibrium curve show?
The relationship between hemoglobin saturation and oxygen partial pressure (PO₂).
What is the significance of the P50 value on an oxygen equilibrium curve?
It represents the PO₂ at which hemoglobin is 50% saturated; a higher P50 indicates lower oxygen affinity.
Why does hemoglobin have a sigmoidal O₂ dissociation curve?
Due to cooperative binding—each bound O₂ increases the affinity of hemoglobin for the next.
Why is myoglobin’s oxygen-binding curve hyperbolic, not sigmoidal?
Because it binds only one oxygen molecule without cooperative effects.
What is the Bohr effect and why is it physiologically important?
Increased CO₂ or lower pH reduces hemoglobin’s O₂ affinity, enhancing oxygen unloading in metabolically active tissues.
How does temperature influence hemoglobin’s oxygen affinity?
Higher temperatures decrease O₂ affinity, promoting oxygen release during activity.
How do organic phosphates like 2,3-DPG affect oxygen delivery?
They decrease O₂ affinity by binding hemoglobin, shifting the dissociation curve right to promote unloading.
Why does fetal hemoglobin bind oxygen more tightly than adult hemoglobin?
It is less sensitive to 2,3-DPG, allowing efficient oxygen transfer from maternal to fetal blood.
List the three main forms of CO₂ transport in the blood.
1) Dissolved in plasma, 2) Bound to hemoglobin (carbaminohemoglobin), 3) As bicarbonate (HCO₃⁻).
What enzyme catalyzes the conversion of CO₂ to bicarbonate in red blood cells?
Carbonic anhydrase.
Explain the Haldane effect in gas exchange.
O₂ binding to hemoglobin promotes CO₂ release, aiding CO₂ unloading in the lungs.
How does the Bohr shift help oxygen delivery in tissues?
It reduces O₂ affinity in response to high CO₂ and low pH, enhancing oxygen unloading.
What drives CO₂ diffusion from tissues into blood?
A higher PCO₂ in tissues compared to blood.
What drives CO₂ diffusion from blood into alveoli?
A higher PCO₂ in blood compared to alveoli.
How do chloride ions participate in CO₂ transport?
They are exchanged with bicarbonate (Cl⁻/HCO₃⁻ shift) to maintain ionic balance during CO₂ transport.
What happens to gas transport dynamics in systemic vs. pulmonary capillaries?
Systemic: PO₂↓, PCO₂↑, pH↓ → O₂ unloading; Pulmonary: PO₂↑, PCO₂↓, pH↑ → O₂ loading.
Where are central chemoreceptors located and what do they detect?
In the medulla; they detect CO₂ and pH changes in cerebrospinal fluid.
Where are peripheral chemoreceptors located and what do they detect?
In carotid and aortic bodies; they detect PO₂, PCO₂, and pH changes.
What is the primary stimulus for increasing ventilation under normal conditions?
Increased PCO₂ is the most potent stimulus for respiration.
At what PO₂ level does oxygen become a strong ventilatory stimulus?
When arterial PO₂ drops below ~60 mm Hg.
