Diffusion is the net movement of a gas or a solute from and area of high concentration to an area of low concentration as a result of the random movement of particles
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Dictionary
Net movement -
Overall movement
Large molecules cannot usually move through a membrane because they are too big but smaller particles will eventually even themselves out throughout a molecule.
Diffusion is the net movement of particles, through particles of air, to an area where they are at a lower concentration
Everyday examples of diffusion
Two everyday examples of diffusion would be:
Toast and deodorant
Two substances that need to get out of cells:
Carbon dioxide and glucose
Two substances that need to get into cells:
Oxygen
Sunlight (rays)
During respiration carbon dioxide is produced in the respiring cell. Explain why carbon dioxide diffuses from the respiring cell into a blood vessel nearby. How does this help the cell survive?
Carbon dioxide diffuses from the respiring cell into a blood vessel near by. Co2 is taken out of respiring cells and put into blood vessels to help the cells survive, it does this because too much co2 is toxic to the human body and if too much of it got into the respiring cells, we would die. If the co2 is placed into a blood vessel it can then be exhaled and the process repeats.
To get into or out of cells, dissolved substances have to pass through the cell membrane around the outside of it. This means only particles that are small enough can get through and particles that are too big cannot get across. Diffusion happens faster if the concentration gradient is bigger or slower if they are smaller.
Other Facts
Dissolved substances and gases can move in and out of a cell using diffusion.
Diffusion occurs more rapidly when there is a larger difference in concentration.
Cells
How do you define a cell?
Definition of a cell -
There are many types of cells, the structure of a cell gives a clue to its function
Examples of cells
Fat cell
Sperm cell
Root hair cell
Facts you should know
Most human cells, like animal cells contain a nucleus, cytoplasm, cell membrane, mitochondria and ribosomes
Plant and algal cells contain everything in an animal cell, plus many also contain cytoplasts and a permanent vacuole filled with sap
Plant cells are different from animal cells because they have different functions
Bacteria are much smaller than plant and animal cells
Yeast is a single celled organism, which is different from plant and animal cells
Cells are specialized to carry out a certain function e.g fat cell, sperm cell.