Diffusion Flashcards
Diffusion
2 marks
Random movement of molecules down the concentration gradient
from an area of higher concentration to an area of lower concentration.
How do substances move in and out of a Cell or Organism?
2 marks
Through a semi-permeable membrane via Diffusion.
Substances that move in and out of Cell via Diffusion
5 marks
Oxygen Carbon Dioxide Water Dissolved Nutrients Urea
Rate of Diffusion is affected by;
3 marks
Concentration Gradient
Temperature
Surface Area
How does the concentration gradient affect rate of diffusion?
(2 marks)
Larger surface area in the high and low concentrations increases the diffusion rate.
How does temperature affect rate of diffusion?
3 marks
High temperature - provides particles with more kinetic energy increasing the diffusion rate.
How does surface area affect rate of diffusion?
2 marks
Larger surface area - through which diffusion can happen - increases the diffusion rate.
What happens as the cells volume increases?
1 mark
More substances are needed for cell reactions.
What happens as the cells surface area increases?
1 mark
Amount of substances diffusing into the cell increases.
Surface area/ Volume ratio (SA/V ratio)
3 marks
Volume and Surface Area increase.
Volume increases faster so much that the surface area available (to allow substances in) halves each time the volume doubles.
Why does the cell die once it reaches its maximum size?
2 marks
Not enough surface area to allow the diffusion of sufficient substances like oxygen.
Why do Organisms need a large surface area?
(Large SA/V ratio)
(1 mark)
To supply substances for cell reactions.
Why have Multi-celled Organisms have developed internal gas exchange organs (lungs)?
(1 mark)
To provide an increased surface area.
Why is the Circulatory System developed to provide all cells with substances? (e.g oxygen)
(1 mark)
Lungs are far away from other body cells which require oxygen.
Concentration
1 mark
The measure of the amount of a substance.
