Exchange surfaces - Cell Biology

Question 1

How is the small intestine adapted for efficient absorption?

Answer 1

• Villi - increases surface area = quick absorption
• Short diffusion distance because each villus has a single layer of surface cells - concentration gradient is constantly maintained.
• Villi - very good blood supply

Question 2

How are the alveoli adapted for efficient gas exchange?

Answer 2

• Massive surface area
• Moist lining for dissolving gases
• Thin walls - short diffusion path
• Good blood supply to maintain concentration gradient

Question 3

How are leaves adapted for exchange?

Answer 3

• Air spaces that surround the leaf cells increase the area in which gas exchange takes place
• Gaurd cells close the stomata when the plant is losing more water - prevents the plant from wilting
• Flattened shape of leaf increases the area of this exchange surface so its more effective

Question 4

How are the roots adapted?

Answer 4

• Root hair cells provide a large surface area
• Vacuole full of concentrated cell ap - creates a steep water potential gradient
• Root hair cells have lots of mitochondria for active transport of mineral ions

Question 5

How are exchange surfaces adapted to maximise effectiveness?

Answer 5

• Thin membrane - substances have a short distance to diffuse
• Large surface area - lots of a substance can diffuse at once
• In animals, exchange surfaces have lots of blood vessels to get things into and out of the blood quickly
• Gas exchange surfaces in animals are often ventilated - air moves in and out

Question 6

How are the gills of a fish adapted?

Answer 6

• Each gill has gill filaments - give a big surface area for exchange of gases
• Gill filaments are covered with lamellae - increase SA even more
• Lamallae have lots of blood capillaries to speed up diffusion
• They have a thin surface layer of cells to minimise diffusion path
• Conc. of oxygen is always higher in the water so the concentration gradient allows oxygen to enter blood
• Blood flows in 1 direction in lamallae and water flows in opposite direction. This maintains a large conc gradient between water and blood

Question 7

How do the gills work?

Answer 7

• Used for gas exchange
• Water (has oxygen) enters from mouth and passes through its gills
• Oxygen diffuses from water into blood
• Carbon dioxide diffuses from blood to water