B8 Exchange surfaces Flashcards
Define diffusion?
Movement of particles from an area of high concentration to an area of low concentration
What are the main factors that affect the rate of diffusion?
Concentration gradient
Temperature
Surface area
Describe how the alveoli are adapted for gas exchange
Millions of alveoli - large surface area
Rich blood supply - maintains concentration gradient
Alveoli close to capillaires - short diffusion distance
Thin walls - short diffusion pathway
Ventilation - maintains concentration gradient
Name two chemicals that diffuse into all cells.
Glucose
Oxygen
Name two chemicals that diffusion out of all cells
Carbon dioxide
Urea
How are single celled organisms adapted for diffusion?
Large surface area to volume ratio
Why do multi-cellular organisms need a ventilation and circulation system?
Surface area to volume ratio is too small
Oxygen and glucose could not diffuse to each ell in the body without them
Define osmosis?
Movement of water from a dilute solution to a concentrated solution
through a selectively permeable membrane
What happens to an animal cell if it is placed in water?
Absorbs water by osmosis
Cytoplasm swells
Cell will eventually burst
What happens to an animal cell if it is place in very strong salt/sugar solution?
Water is lost by osmosis
Cytoplasm shrinks
Cell becomes crenated
What happens to plant cells if they are placed in water?
Absorb water by osmosis
Become turgid
Cell wall prevents bursting
What happens to plant cells if they are placed in very strong salt/sugar solution?
Water is lost by osmosis
Cytoplasm shrinks
Cell becomes flaccid
Describe how the gills of a fish are adapted for gas exchange
Large surface area
Thin gill walls - short diffusion distance
Good blood supply - maintains concentration gradient
Blood capillaries are close to water - short diffusion distance
Counter current flow - blood and water flow in opposite directions.
Describe how the small intestine wall is adapted for rapid diffusion
Villi - increase surface area
Good blood supply - maintains concentration gradient
Close blood supply - short diffusion distance
Thin walls - short diffusion distance
How is the surface area to volume ratio of a cube calculated?
Surface area = 6 (width x length)
Volume = length x width x depth
Ratio = surface area / volume
What happens to the surface area to volume ratio as an organism gets bigger?
SA:V gets smaller
Organism needs to develop a gas exchange system and circulation system
Define active transport
Movement of substances from a more dilute solution to a more concentrated solution
How is a root hair cell adapted to absorb mineral ions?
Large surface area
Lota of mitochondria to provide energy
Name the chemical absorbed by the roots by active transport
Mineral ions eg nitrate
Name a molecule absorbed by active transprot in the gut
Sugar
Give a differnece between diffusion and active transport
Active transport requires enregy whereas diffusion does not
Active transport moves molecules from a low concentration to a higher concentration whereas diffusion moves molecules from a high concentration to a low concentration
Give a difference between osmosis and diffusion
Osmosis is the movement of water whereas diffusion is the movement of any chemical
State the equation for working out percentage change in mass
change in mass x 100
initial mass
How is a root hair cell adapted to absorb water?
Large surface area
