UNIT 1 - Transport Across Membranes Flashcards
the cell membrane contains:
- phospholipid molecules (double layer)
* patchy mosaic of protein molecules
how can substances move in or out of a cell?
- diffusion
- osmosis
- active transport
name two types of passive transport.
diffusion and osmosis.
describe passive transport.
passive transport is the movement of a substance down a concentration gradient. this does not require energy.
why do cells use diffusion?
so they can move useful substance into the cell and waste products out.
name useful substances needed by cells. (3)
- glucose
- oxygen
- amino acids
name waste products removed from cells. (2)
- carbon dioxide
* urea
describe osmosis.
the diffusion of water. does not require energy.
what affects whether the cell loses or gains water?
the water concentration of the solution outside of the cell.
osmotic effects on animal cells - normal red blood cell - pure water
water goes into cell, cell bursts.
osmotic effects on animal cells - normal red blood cell - weak salt solution.
cells are the same, no movement, so no change.
osmotic effects on animal cells - normal red blood cell - strong salt solution
water goes out of cell - so cell shrinks.
osmotic effects on plant cells - normal plant cell - pure water.
water passes into cell, cell becomes turgid (filled).
osmotic effects on plant cells - normal plant cell - weak sugar solution
concentration in and out cell are the same, no movement.
osmotic effects on plant cells - normal plant cell - strong sugar solution.
water passes out of cell becomes plasmolysed.
