diffusion and osmosis Flashcards
(20 cards)
What is diffusion?
The passive movement of particles from an area of high concentration to an area of low concentration.
Does diffusion require energy?
No, it is a passive process.
What types of substances move by diffusion?
Oxygen, carbon dioxide, water (osmosis), nutrients, and mineral ions.
What factors affect the rate of diffusion?
Temperature, surface area, concentration gradient.
What material is used to observe diffusion?
Agar blocks containing dye.
What trend was observed in the experiment?
Smaller blocks with a higher SA:V ratio diffused faster.
Why do cells tend to be small?
To maximise their surface area-to-volume ratio for efficient diffusion.
What is osmosis?
The diffusion of water from a dilute solution to a concentrated one through a selectively permeable membrane.
What happens to animal cells in pure water?
They swell and may burst (lysis).
What happens to plant cells in pure water?
They become turgid due to increased turgor pressure.
What is plasmolysis?
When plant cells lose water, shrink, and the membrane pulls away from the wall.
What is used to test osmosis in this practical?
Potato cylinders and different concentrations of sucrose.
How is osmosis measured?
By change in mass or length of the potato cylinders.
What does it mean if the mass doesn’t change?
The sucrose concentration is equal to the potato’s internal concentration.
What is Visking tubing used for?
To model a selectively permeable membrane in osmosis.
What is transpiration?
The evaporation of water from spongy mesophyll cells and its diffusion out of stomata.
What is the transpiration stream?
Continuous movement of water from roots to leaves.
Name 3 roles of the transpiration stream.
Supplies water for photosynthesis, transports minerals, provides turgor.
What is the purpose of the washing line method?
To measure water loss from leaves under different conditions.
Why is petroleum jelly used on cut stalks?
To prevent water loss from the stalk, isolating loss from the leaf surface.
