lesson 15 transcript + study guide Flashcards
pulmonary pathway of blood in mammals?
Deoxygenated blood from the right ventricle
pulmonary arteries
lungs
oxygenated in alveoli
pulmonary veins
left atrium
gas exchange occur in mammals?
alveoli
hemoglobin
protein in red blood cells that binds and transports oxygen
How many oxygen molecules can one hemoglobin bind?
4
1 per heme group
What is the Bohr effect
Lower pH or higher temperature decreases hemoglobin’s affinity for O₂, enhancing oxygen release to tissues
What happens to hemoglobin during exercise
More O₂ is released due to lower pH and higher temperature; the dissociation curve shifts right
What form carries most CO₂ in the blood
Bicarbonate ions (HCO₃⁻) in plasma
How is CO₂ converted into bicarbonate?
CO₂ + H₂O ⇌ H₂CO₃ ⇌ H⁺ + HCO₃⁻ (catalyzed by carbonic anhydrase)
What is the chloride shift
Bicarbonate exits RBCs into plasma in exchange for chloride ions
What increases the efficiency of alveolar gas exchange?
High surface area (~70 m²), thin walls (1 cell), and close capillary contact
What surrounds each alveolus
A dense capillary network for gas exchange
What keeps alveoli from collapsing?
Surfactant reduces surface tension on alveolar walls
countercurrent exchange in gills?
Water flows opposite to blood flow in lamellae to maintain an oxygen gradient
Why is countercurrent exchange more efficient than concurrent exchange?
It allows more complete O₂ absorption, up to 85%
Do alveoli use countercurrent exchange?
No, alveoli use passive diffusion with cross-flow, not true countercurrent flow
How do diving mammals conserve oxygen?
they have high hemoglobin & myoglobin, large blood volumes, and slow their heart rate (bradycardia)
How is oxygen prioritized during a dive?
Blood is directed mainly to the brain and heart
What primarily triggers faster, deeper breathin
A rise in CO₂, not low O₂
How does CO₂ affect blood pH?
CO₂ forms carbonic acid → H⁺ ions lower pH → triggers chemoreceptors
Where are the chemoreceptors located?
In the medulla, carotid arteries, and aorta
What part of the brain regulates breathing?
The medulla oblongata
What are the three ways CO₂ is transported in the blood?
8% dissolved in plasma
20% bound to hemoglobin (not the iron)
72% as bicarbonate (HCO₃⁻)
What happens to bicarbonate at the lungs
The reaction reverses → CO₂ is reformed and exhaled
What does the oxygen dissociation curve show?
The % of hemoglobin saturated with O₂ at different PO₂ levels
What causes the curve to shift right?
Low pH, high CO₂, high temperature (Bohr effect)
What is the chemical equation for CO₂ transport in blood?
CO₂ + H₂O ⇌ H₂CO₃ ⇌ H⁺ + HCO₃⁻
