gas exchange Flashcards
What is one feature of an efficient exchange surface?
Good blood supply
Give two ways the alveoli in the lungs are adapted for efficient gas exchange
They have a large surface area
They have thin walls (one cell thick)
Explain how the villi in the small intestine help increase the rate of diffusion of nutrients into the blood.
Villi increase the surface area of the small intestine (1)
They have thin walls for a short diffusion distance (1)
They have a good blood supply to maintain a concentration gradient (1)
This helps nutrients diffuse quickly into the blood (1)
Fish have gills with a large surface area and a good blood supply. Explain how this helps the fish absorb oxygen efficiently.
A large surface area means more oxygen can diffuse at once (1)
A good blood supply keeps oxygen levels low in the blood (1)
This maintains a steep concentration gradient so oxygen keeps diffusing in (1)
Explain why this is true, and how the body prevents this from happening.
Once the concentrations of oxygen inside the blood and in the alveoli are the same, diffusion stops.”
Diffusion happens from a high to low concentration (1)
If the concentration of oxygen is the same in the blood and alveoli, there is no concentration gradient (1)
So no net diffusion of oxygen will occur (1)
The body prevents this by constantly circulating blood, which removes oxygen from the lungs (1)
Having a large surface area means…
Having a large surface area means molecules can travel across at the same time. Therefore rate of diffusion is higher
If the exchange surface is very thin that means…
If the exchange surface is very thin that means there is a short distance therefore diffusion can take place quickly
e.g in root hair cell water only has to diffuse in a thin cell wall and cell membrane to get into the plant.
Short diffusion meaning
short diffusion is when diffsion can take place quickly due to thin surfaces of the cell
What does good blood supply maintain?
Good blood supply maintain concentration gradient
