Unit 3 Flashcards
What is gas exchange?
Gas exchange is the process by which all organisms absorb one gas from the environment and release another.
Give an example of gas exchange in redwood trees.
Redwood trees absorb CO2 for photosynthesis and emit O2.
What is diffusion and why is it important for gas exchange?
Diffusion is the basis of gas exchange, a relatively slow process that is maximized by increasing surface area and decreasing diffusion length.
How does diffusion work in small organisms?
Small organisms have a large surface area to volume ratio and a small distance between the organism’s center and exterior environment, allowing the outer surface of the cell to be used for gas exchange.
How does diffusion work in large organisms?
Large organisms have a small surface area to volume ratio and a large distance between the organism’s center and exterior environment, requiring a specialized gas exchange surface like alveoli in the lungs.
What are the four properties of gas exchange surfaces?
- Permeable: Allows free diffusion of O2 and CO2.
- Large: Large surface area relative to volume.
- Moist: Covered by a thin layer of moisture to dissolve gas.
- Thin: Gases diffuse over a short distance, usually through a single-layer of cells.
Why is a concentration gradient important in gas exchange?
Diffusion only occurs because of a concentration gradient; it must be maintained for efficient gas exchange.
How is a concentration gradient maintained in the alveoli?
CO2 diffuses out of the blood into the alveoli because the concentration of CO2 in the air is less than in the blood.
How do small, aerobically-respiring organisms maintain concentration gradients?
Cell respiration continually uses oxygen, producing CO2, maintaining higher CO2 and lower O2 concentrations inside the cell compared to outside.
How do large organisms like mammals maintain concentration gradients?
Through aerobic respiration, flowing through dense capillary networks and organs, maintaining high CO2 and low O2 concentrations in the blood relative to air.
What is ventilation?
Ventilation is the movement of air in and out of the lungs and water across the gills.
How does ventilation help maintain concentration gradients in mammals?
Mammals periodically inhale and exhale, preventing high CO2 and low O2 concentrations in the lungs. The rate of ventilation is adjusted based on CO2 concentration in the blood.
How does ventilation work in fish?
Fish take in water through their mouth, pump it across their gills, and out their gill slits, with blood flowing in the opposite direction to maintain high O2 and low CO2 concentrations.
Describe the structure of the pulmonary alveolus.
Pulmonary alveoli have a diameter of 0.2-0.5 mm, with walls about 0.2 micrometers thick, mostly covered by capillaries, and supported by collagen and elastic fibers.
What is the function of pulmonary surfactant?
Pulmonary surfactant, secreted by cells on the alveolus walls, reduces surface tension and prevents the lungs from collapsing by forming a moisture layer.
