Diffusion Flashcards
What is diffusion?
The intermingling of substances by natural movement of their particles
What 3 things can speed up diffusion?
Temperature
Give them space
Kinetic energy
Ammonia vapour through a tube experiment
What is the method?
- Place Cotten wool in a tube and close the tube using rubber bungs
- Set timer immediately
- After 5 seconds record the length on the tube where the red litmus paper has turned blue
- Repeat every 5 seconds until it stops
Ammonia vapour through a tube experiment
When the ammonia vapour if given off the alkaline can be detected by what?
Using red litmus paper that turned blue when ammonia reaches it
Ammonia vapour through a tube experiment
What is the independent variable?
Time
Ammonia vapour through a tube experiment
What is the dependent variable?
Distance etc…
Ammonia vapour through a tube experiment
What sort of graph should be drawn and why?
Line graph
Because the independent and dependent variable are both numbers
Ammonia vapour through a tube experiment
Describe the results on the graph, what do you notice happening?
Between 5s and 20s it has diffused 14mm. After first diffusing it slowed down, between 30s and 40s it was only diffusing 5mm
Ammonia vapour through a tube experiment
Explain the results of this experiment
At the beginning there was a high concentration gradient so diffusion took place quickly.
Towards the end of the experiment the concentration gradient was low, so diffusion took place slowly
Does diffusion use up energy?
No
Name 3 examples of diffusion in living organisms
- Carbon dioxide diffuses from the blood circulating around the lungs
- Oxygen diffuses from blood cells in the blood streams into muscles
- In pregnancy food/Oxygen diffuses into baby via placenta
Describe how a red blood cell has adapted to make diffusion quicker and faster?
Larger surface area
Concave to be faster
Phenolphthalein pink agar experiment
What’s the aim of the experiment?
Carry out an investigation into how the surface area to volume ratio of agar blocks effect the rate of diffusion
Phenolphthalein pink agar experiment
What’s your hypothesis for this experiment?
The bigger the square the longer it will take to diffuse
Phenolphthalein pink agar experiment
Evaluation for this experiment
The phenolphthalein agar cubes volume increased it takes longer to diffuse, because of the volume: surface area ratio
Phenolphthalein pink agar experiment
Is there any possible errors in this experiment?
The cubes won’t be cut exactly
Why is diffusion important?
It is the main way in which living organisms obtain the things they need and get rid of their waste products.
Most single celled animals are less than 1mm across and the largest are only about 2mm long. Explain this?
It requires oxygen for diffusion, if it is to big it can’t get the oxygen because all compared to the volume ratio
What is osmosis?
Osmosis is the next movement of the water from a high water concentration to a low water concentration a perticually permeable membrane
What state does osmosis take place?
Water
Explain the results in a osmometer?
Water particles come in, but the sugar is to tick to come out. Liquids rises up the tube
What will happen to red blood cells if they are placed in a solution of distilled water?
(Animal cells)
There would be too much water so it would pop
Explain why an animal cell would pop?
- Net diffusion of water into cell, so cell swells and bursts
- No net diffusion of water, so cell is normal size
- Net diffusion of water out of cell, so the cell shrinks
Plant cells do not burst in placed on distilled water, why?
Plant cells
The cell wall will stop to much water from entering so it won’t pop
Explain why a plant cell will not pop
- Net diffusion of water into cell, so cell becomes turgid
- No net diffusion of water, so cell is normal size
- Net diffusion of cell water so cytoplasm shrinks from cell wall and plasmolyses
What does passive mean?
It doesn’t require a lot of energy
What does active transport mean?
It is the movement of a substance from a low to high concentration across a cell membrane. This process requires energy released by respiration
Give two main differences between diffusion and active transport?
- Active transport is the movement against a concentration gradient
- Active transport requires energy from respiration
Why do you cells that carry a load of active transport have a lot of mitochondria?
Mitochondria a is where most of respiration takes place so the more mitochondria you have the more active transport there is.
Where does the energy for active transport come from?
Respiration is were the energy comes from
