Transport Across Cell Membranes Flashcards
What is diffusion
The passive movement of a substance from an area of high concentration to an area of low concentration down a concentration gradient
What is the cell membrane
A fluid structure composed of fats and proteins + controls what enters and leaves a cell
What are the substances that enter and leave the cell by diffusion
Enter: oxygen and food
Leave: CO2
Why is the cell membrane selectively permeable
As they have tiny pores which allows small substances to move through (eg water) and not large ones (eg protein)
What is osmosis
The passive movement of water molecules from am area of high water concentration to an area of low water concentration across a selectively permeable membrane
What is the effect of placing a plant and animal cell in pure water, dilute solution and a strong solution
Pure water: water moves from a high concentration to a low concentration inside by osmosis, the cell swells up and becomes turgid
Dilute solution: no effect: concentration inside and outside are the same
Strong solution: water moves from a low concentration to a big concentration, cell shrivels up and becomes plasmolysed
What is passive transport
The movement of a substance with the concentration gradient and requires no energy
Give examples of passive transport
Diffusion
Osmosis
What is active transport
The movement of a substance against the concentration gradient and requires energy- membrane proteins are needed
Give examples of substances that move by active transport
ions - sodium
