Exchanging substances

Explain how gas exchange happens in the lungs?

Explain how gas exchange happens in the lungs?

• Transfers oxygen to the blood and remove carbon dioxide from it

• Use alveoli for diffusion

How are the alveoli specialised to maximise diffusion?

• Large surface area

• Moist lining for dissolving gases

• Very thin walls

• A good blood supply

Where are the villi found and what are they used for?

Found in the small intestine to increase diffusion and active transport of nutrients

How are the villi adapted to maximise diffusion and active transport?

• Millions of villi

• Increase the surface area to maximise absorption

• A single layer of surface cells

• a very good blood supply

What is diffusion used for on a plants leaves?

carbon dioxide diffuses into the air spaces within the leaves and then into the cells where photosynthesis happens

What are the exchange surfaces on leaves called?

Stomata

What diffuses out of stomata and why?

Oxygen and water vapour because they are the products of photosynthesis

Explain what guard cells are and where they are found?

Controls the size of stomata by opening or closing them to control a plants water lose in comparison to its water absorption in the roots. Found inside of stomata

How are leaves adapted to maximise diffusion?

• stomata

• flattened shape to increase surface area

• walls of cells act as an exchange surface

• air spaces inside the leaf increase area increasing chances of carbon dioxide absorption

How does water loss occur through the stomata?

• the water vapour evaporates from cells inside the leaf

• it escapes by diffusion because the concentration gradient is lower outside than inside the leaf

What are the exchange surfaces on fish?

Gills

What and how substances are exchanging through the gills of a fish?

Water enters the fish through its mouth and passes out through the gills. As this happens oxygen diffuses from the water into the blood in the gills and carbon dioxide diffuses from the blood into the water

How are the gills adapted to maximise diffusion?

• Gil filaments: increase the surface area

• Lamellae: further increase the surface area by covering the filaments

• Lots of blood capillaries: speed up diffusion

• thin surface layer of cells: minimise the distance of diffusion

• Blood vs water flow directions: blood flows through the lamellae in one direction and water flows in the opposite direction to maintain the concentration gradient

• Oxygen concentration in the water is always higher than in the blood