Movement Of Substances Flashcards
(10 cards)
How does water move into and out of cells by osmosis
Tissue fluid surrounds body (water with oxygen, glucose etc. dissolved). It’s squeezed out of bloody capillaries to supply cells with everything they need
Tissue fluid has different concentration to fluid inside a cell so water either moves into cell or out of cell by osmosis
Cell short of water = solution inside concentrated so exterior solution more dilute - water moves into cell
Cell plenty of water = interior more dilute so water drawn into fluid
Effect of surface area to volume ratio on rate of movement of substances
Higher with larger surface to volume ratio
Effect of concentration gradient on rate of movement of substances
Faster movement if steeper concentration gradient (doesn’t affect active transport - only osmosis and diffusion)
Effect of a turgid cell on a plant
When plant well watered, all cells draw in water by osmosis so become plump/ swollen
Contents of cell push against cell wall (Turgor pressure) so supports plant tissues
Effect of flaccid cell on plant
If no water in soil, plant starts to wilt because cells start to lose water- lose Turgor pressure
INELASTIC CELL WALL prevents plant completely losing shape
Why doesn’t a unicellular organism need transport systems?
Can rely on diffusion to move substances in and out of cells as has large surface area to volume ratio so nutrients etc can pass quickly through membranes and around organism
Why does a multicellular organism need transport systems
Small surface area compared to volume so need specialized exchange surfaces and transport systems
Experiment to test for diffusion in a non-living system
- make up agar jelly with phenolphthalein and dilute NaOH so jelly turns pink
- fill beaker with dilute HCl and using scalpel cut cubes and place in acid
- leaves cubes for while and turn colorless as acid diffuses into the jelly, neutralizing the NaOH
Test for Osmosis in living system
-cut up potato into identical cylinders and prepare beakers with different sugar solutions (water -> v. Concentrated sugar solution)
-measure length of cylinders, leave few in each breaker for approx half an hour then remove and remeasure lengths
-if water drawn in = longer
if drawn out = shrunk
Test for osmosis in non-living system
- tie piece of wire around one end of some visking tubing and put glass tube in other end - fix tubing around it with wire
- pour sugar solution down glass into tubing
- leave overnight then measure where liquid is (water should be drawn in by osmosis and elk force water up glass tube)
