Section 1: Movement of Substances in and out of cells Flashcards
Osmosis, diffusion, active transport and experiments
What is diffusion
The net movement of particles from an area of high concentration to an area of low concentration
What is osmosis
The net movement of water molecules from an area of high water potential to an area of low water potential across a partially permeable membrane
What is active transport
The net movement of particles against the concentration gradient (low concentration to high concentration) using energy released during respiration
What type of movement is osmosis and diffusion
passive (doesn’t require energy)
What are the factors that effect the movement of substances
temperature
distance
concentration gradient
SA:V ratio
How does distance effect the rate of movement
The shorter the distance the faster the rate of movement in and out of cells
How does temperature effect the rate of movement
The higher the temperature the more kinetic energy the particles have so they will move faster in and out of cells
How does the concentration gradient effect the rate of movement
Particles will move faster in and out of cells if there is a big difference in concentration between the inside and outside of the cell
Which movements does concentration gradient effect
osmosis and diffusion
How does the surface area to volume ratio effect the rate of movement
The larger the SA:V ratio the faster the movement in and out the cell
What size cube has a big SA:V ratio
the smaller the cube the larger the ratio
Describe an experiment to investigate diffusion using non-living systems
- Make up some agar jelly, the jelly should be a shade of pink
- Pour some Hydrochloric acid into a beaker and add the a few cubes of agar jelly
- Leave the cubes and eventually they will turn colourless
Why does the agar jelly turn colourless
The acid diffuses into the agar jelly and neutralises the sodium hydroxide (what makes the jelly pink)
Describe how to investigate osmosis using living systems
- Get 2 beakers and fill one with concentrated sugar solution and one with pure water.
- Measure 6 potato strips and put 3 in each into each beaker
- Leave for half an hour or so and then remeasure the potato strips
What should happen to the potato strips in the water and in the sugar solution and why
The potato strips in the water should increase in length because the water concentration in the potato is lower then in the water so because of osmosis the water goes into the potato.
In the sugar solution the potato should shrink because it has a higher water potential then the sugar solution so because of osmosis the water moves out of the potato.
