2. Gas Exchange Flashcards
What is a gas exchange surface?
A boundary between the outside environment and the internal environment of an organism.
Organisms need carbon dioxide and oxygen to diffuse across gas exchange surfaces quickly.
What 2 things do gas exchange surfaces have in common that increase rate of diffusion?
Large surface area.
They’re thin - often one layer of epithelial tissue.
They provide short diffusion pathway across gas exchange surface.
What other factor also increases the rate of diffusion?
Organism maintains a steep concentration gradient of gases across the exchange surface.
What is gas exchange lie in a single-celled organism?
Single-celled organisms absorb and release gases by diffusion through their cell-surface membranes.
Large surface area, a thin surface and short diffusion pathway - no need for specialised gas exchange system.
What is gas exchange like in a fish?
Lower concentration of oxygen in water than in air.
Fish have special adaptations to get enough of it.
Gas exchange surface is in gills.
What is the structure of a fish’s gills like?
Water which contains oxygen enters the fish through mouth and passes out through gills.
Each gill is made from lots of thin plates called gill filaments which give large surface area to exchange gases and speeds up rate of diffusion.
Gill filaments covered in lots of tiny structures called lamellae - increase surface area even more.
Lamellae have lots of blood capillaries and thin surface layer of cells to speed up diffusion between water and blood.
BREAKDOWN.
What is each gill made of?
Lots of thin plates called gill filaments that give large surface area and speed up rates of diffusion.
BREAKDOWN.
What are gill filaments covered in?
Tiny structures called lamellae which increase surface area.
BREAKDOWN.
What do the lamellae have?
Lots of blood capillaries and a thin surface layer of cells to speed up diffusion between water and blood.
Where are the gills located on a fish?
Inside the fish’s head underneath gill slits or bony flap called operculum.
What is counter-current system?
When blood flows through the lamellae in one direction and water flows over them in the opposite direction.
Means water with with high oxygen concentration always flows next to blood with lower concentration o oxygen.
Maintains a steep concentration gradient between water and blood.
Describe gas exchange in dicotyledonous plants.
Plants need CO2 for photosynthesis, this produces oxygen as a waste gas.
They need oxygen for respiration, this produces carbon dioxide as a waste gas.
Main gas exchange surface is in the mesophyll cells in the leaf.
How are mesophyll cells adapted to their function of gas exchange?
They have a large surface area.
How do gases get into and out of the leaf?
Through special pores in the epidermis (usually the lower) called the stomata.
Stomata opens to allow exchange of gases and closes if the plant is losing too much water.
Guard cells control opening and closing of stomata.
What does dicotyledonous plants mean?
Green.
Non-woody plants, bushes and trees.
