Movement Across Membranes Flashcards
(15 cards)
Why can substrates pass through cell membranes?
Cell membranes are partially permeable, enabling some molecules to pass through.
By what three methods can different substances pass through cell membranes?
•Diffusion
•Osmosis
• Active Transport
What is diffusion?
The net movement of molecules from an area of high concentration to an area of low concentration down a concentration gradient
Why is diffusion described as a passive process?
It does not require energy
What substances can pass through cell membranes by diffusion?
Small molecules .e.g. carbon dioxide, oxygen
What two factors affect the rate of diffusion?
•Temperature
•Concentration gradient
How does temperature affect the rate of diffusion?
The higher the temperature, the more energy possessed by molecules and the faster the rate of diffusion.
How does concentration gradient affect the rate of diffusion?
The steeper the concentration gradient, the faster the rate of diffusion.
What is osmosis?
The net movement of water molecules from an area of high water (low solute) concentration to an area of low water (high solute) concentration across a partially permeable membrane
Describe what happens to an animal cell if it is placed into a more dilute solution
•higher concentration of water in surrounding solution
•water enters by osmosis .
•pressure inside cell increases . . Cell bursts
Describe what happens to a plant cell if it is placed into a more dilute solution
•higher concentration of water in surrounding solution.
•water enters by osmosis.
• cell wall resists increase in pressure Cell turgid.
Describe what happens to an animal cell if it is placed into a more concentrated solution
•lower concentration of water in surrounding solution
•water leaves cell by osmosis
•pressure inside cell decreases. Cell shrinks
Describe what happens to a plant cell if it is placed into a more concentrated solution
•Lower water concentration in surrounding solution
•water leaves cell by osmosis
•pressure inside cell decreases. Cytoplasm shrinks
•cytoplasm pulls away from cell wall-plasmolysis
Describe what happens to a cell wall if it is placed into a solution of equal water concentration
No net movement of water molecules into or out of the cell
What is active transport?
The moment of molecules across a cell membrane from an area of low concentration to an area of high concentration, against the concentration gradient, using energy
