Movement In and Out of Cells Flashcards
What is osmosis?
The net movement of water particles across a partially permeable membrane from an area of high concentration to an area of low concentration
What is active transport?
The movement of particles from an area of low concentration to an area of high concentration (against a concentration gradient) using energy released during respiration
What term is used to describe plant cells which are well watered (plump and swollen)?
Turgid
What term is used to describe plant cells which are not well watered (start to droop and wilt)?
Flaccid
Why is it important that a plant has turgid cells?
Because the contents of the cells push against the cell wall, creating turgor pressure. This helps support the plant tissue.
What part of the plant helps support the plant tissue when the cells are flaccid?
The inelastic cell wall
What is diffusion?
The net movement of particles from an area of high concentration to an area of low concentration
Which three factors affect the rate of movement in and out of cells?
Surface area to volume ratio
Temperature
Concentration gradient
How does the surface area to volume ratio affect the rate of movement in and out of cells?
The rate of diffusion, osmosis or active transport is higher in cells with a larger surface area to volume ratio. This means substances can move in and out of the cell faster.
How does temperature affect the rate of movement in and out of cells?
As the particles get warmer, they have more kinetic energy, so move faster
How does the concentration gradient affect the rate of movement in and out of cells?
Substance move in and of of cells faster if there’s a big difference in concentration between the inside and outside of the cell
Explain why small, unicellular organisms do not need a transport system
Simple, unicellular organisms can rely on diffusion for moving substances in and out of cells, because they have:
- a large surface area to volume ratio and
- a short diffusion distance
so are able to supply the entire organism
Explain why large, multicellular organisms do need a transport system
Large, multicellular organisms can’t rely on diffusion directly into and out of cells because:
- it would be too slow to reach every cell in the organism’s body and
- there’s a small surface area to volume ratio
Therefore large, multicellular organisms require a transport system
Describe an experiment to investigate diffusion in a non-living system
- make up some agar jelly with phenolphthalein indicator and dilute sodium hydroxide - it will be pink
- fill a beaker with some dilute hydrochloric acid
- using a scalpel, cut up the jelly into cubes and put them in the beaker of acid
- if you leave the cubes for a while, they’ll eventually turn colourless and the acid diffuses into the jelly and neutralises the sodium hydroxide
Describe an experiment to investigate osmosis in a living system
- cut up a potato into identical cylinders and get some beakers with different sugar solutions in them (one should be pure water, another should be very concentrated, with a few in between)
- measure the lengths of the cylinders and leave a few cylinders in each beaker for half and hour
- take them out and measure their lengths again
- the potato in pure water will have taken in water
- the potato in sugar will have shrunk
