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Chapter 6: Diffusion and Osmosis - Coggle Diagram
Chapter 6: Diffusion and Osmosis
Diffusion
Diffusion is the net movement of atoms or molecules from a region of higher concentration to a region of lower concentration
Examples
Diffusion in gases such as the aroma of perfume
Diffusion of liquids
Diffusion through a fully permeable membrane
Diffusion through a partially permeable membrane
Osmosis
Osmosis is the net movement of water molecules from a region of higher water potential to a region of lower water potential
Water potential
Water potential is the measure of the tendency for water molecules to move from one place to another
A dilute solution would have more water molecules per unit volume than a concentrated solution, and hence, would have a higher water potential.
Water molecules always move from a region of higher water potential to a region of lower potential
Osmosis can only be carried out by a partially permeable membrane
Large molecules like starch molecules, sucrose molecules and complex sugar molecules are not able to pass through a partially permeable membrane
Diffusion in Cells
Amoeba
In the amoeba, it carries out respiration by letting oxygen diffuse in and carbon dioxide is diffused out when respiration occurs
Plant cells
Plants carry out photosynthesis and during photosynthesis they take in carbon dioxide so carbon dioxide diffuses into the cell while oxygen diffuses out of the cell
Osmosis in plant cells
Plant cell membranes are partially permeable while plant cell walls are fully permeable
If a plant cell is placed in a solution of higher water potential, water molecules enter the vacuole through osmosis so the vacuole increases in size, causing the cell wall to stretch, the water molecules will continue to enter the cell until the cell wall cannot stretch anymore, the pressure exerted by water molecules on the cell wall is called turgor pressure
If a plant cell is in a solution of lower water potential, water molecules leave the vacuole through osmosis so the vacuole loses water and decreases in size. The shrinkage of the cytoplasm from the cell wall is known as plasmolysis, the cell in this state is called plasmolysed, plasmolysed tissues are limp and they will be killed if they remain plasmolysed for too long
Osmosis in animal cells
Animal cells have a cell membrane but do not have a cellulose cell wall, so if they are placed in water, when water enters the red blood cell through osmosis, the red blood cell will swell up and burst
If red blood cells are places in a solution with a lower water potential,water molecules leave the cell through osmosis and the cell would shrink and crinkle