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| #Activity No #2 '''Concept Name - Activity No.''' | | #Activity No #2 '''Concept Name - Activity No.''' |
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− | ==Concept #== | + | ==Concept #== - Diffusion |
| ===Learning objectives=== | | ===Learning objectives=== |
| + | #Transport of materials in plant and animal cells takes place through different processes. |
| + | #In diffusion movement of molecules take place from a region of higher concentration to a region of lower concentration. |
| + | #3.Diffusion is seen in both lower and higher organisms. |
| ===Notes for teachers=== | | ===Notes for teachers=== |
| + | #Movement of materials or molecules in all living organisms take place through diffusion. |
| + | #In diffusion movement of molecules take place from a region of higher concentration to a region of lower concentration. |
| + | #Diffusion is the net movement of a substance (e.g., an atom, ion or molecule) from a region of high concentration to a region of low concentration. This is also referred to as the movement of a substance down a concentration gradient. A gradient is the change in the value of a quantity (e.g., concentration, pressure, temperature) with the change in another variable (e.g., distance). For example, a change in concentration over a distance is called a concentration gradient, a change in pressure over a distance is called a pressure gradient, and a change in temperature over a distance is a called a temperature gradient. |
| + | #An example of a situation in which bulk flow and diffusion can be differentiated is the mechanism by which oxygen enters the body during external respiration (breathing). The lungs are located in the thoracic cavity, which is expanded as the first step in external respiration. This expansion leads to an increase in volume of the alveoli in the lungs, which causes a decrease in pressure in the alveoli. This creates a pressure gradient between the air outside the body (relatively high pressure) and the alveoli (relatively low pressure). The air moves down the pressure gradient through the airways of the lungs and into the alveoli until the pressure of the air and that in the alveoli are equal (i.e., the movement of air by bulk flow stops once there is no longer a pressure gradient). |
| + | The air arriving in the alveoli has a higher concentration of oxygen than the “stale” air in the alveoli. The increase in oxygen concentration creates a concentration gradient for oxygen between the air in the alveoli and the blood in the capillaries that surround the alveoli. Oxygen then moves by diffusion, down the concentration gradient, into the blood. The other consequence of the air arriving in alveoli is that the concentration of carbon dioxide in the alveoli decreases (air has a very low concentration of carbon dioxide compared to the blood in the body). This creates a concentration gradient for carbon dioxide to diffuse from the blood into the alveoli. |
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| ===Activities=== | | ===Activities=== |
− | #Activity No #1 '''Concept Name - Activity No.''' | + | #Activity No #1[[Structure_of_cell_Cell_Activity1|Diffusion]] |
| + | {{subst:science-activity}} |
| #Activity No #2 '''Concept Name - Activity No.''' | | #Activity No #2 '''Concept Name - Activity No.''' |
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