1. Define Diffusion!
-. Diffusion is the movement of particles from a higher concentration region to
a lower concentration region (or can be called as "down a concentration
gradient").
2. Discuss the importance of diffusion in nutrient uptake and gaseous exchange in
plants and humans!
-. Diffusion is important for humans because the lungs' cells exchange oxygen and
carbon dioxide through diffusion. Moreover, digested food substances, such as
amino acids and glucose diffuse through the villi into the blood capillaries.
-. For plant cells, diffusion is used for oxygen intake and carbon dioxide removal.
3. Define Osmosis!
-. Osmosis is the movement of water molecules from a higher water potential
solution to a lower water potential solution, across a partially permeable
membrane.
4. Discuss the effects of osmosis on plant and animal tissues!
-. When placed in a low water potential solution, animal cells will shrink and have
little spikes appear on the cell surface membrane. The crenated cell will
become dehydrated and, eventually, die.
-. When placed in a high water potential solution, animal cells will swell and
burst.
-. For plant cells, its cytoplasm will shrink away from the cell wall when it placed
in a low water potential solution due to outward osmotic flow of water.
This event called plasmolysis which causes tissues to become limp or flaccid.
Plant cells will be killed if they remain plasmolysed for too long.
-. When plant cells place in a high water potential solution, such as distilled
water, its vacuole will increase in size as water is going in and push the cell
contents against the cellulose cell walls. Since the cell wall is strong and
relatively inelastic, it prevents over-expansion of the cell and, also, prevents
the entry of more water. The plant cells will expand and become turgid.
PS : *. The turgor pressure, that keeps the cell turgid, helps to maintain the shape of
soft tissues in plant and keep them firm and erect. The surrounding cells pushed
against each other creating support for the plant.
*. Other function of the turgor pressure :
a). To make some flowers open during the day and close at night.
b). Due to the changes in turgor of the guard cells, the stomata in the plant
opens and closes.
c). The changes in turgor of cells in the small swellings at the base of
the leaflets of mimosa plant causes them to fold when they are touched.
5. Define Active Transport!
-. Active Transport is the substances movement against a concentration gradient
which is from a lower concentration region to a higher concentration region;
and it is an energy-consuming process.
-. Example : It is important for root hair cells to absorb dissolved mineral salts and
for the small intestine cells to absorb glucose and amino acids.
little spikes appear on the cell surface membrane. The crenated cell will
become dehydrated and, eventually, die.
-. When placed in a high water potential solution, animal cells will swell and
burst.
-. For plant cells, its cytoplasm will shrink away from the cell wall when it placed
in a low water potential solution due to outward osmotic flow of water.
This event called plasmolysis which causes tissues to become limp or flaccid.
Plant cells will be killed if they remain plasmolysed for too long.
water, its vacuole will increase in size as water is going in and push the cell
contents against the cellulose cell walls. Since the cell wall is strong and
relatively inelastic, it prevents over-expansion of the cell and, also, prevents
the entry of more water. The plant cells will expand and become turgid.
PS : *. The turgor pressure, that keeps the cell turgid, helps to maintain the shape of
soft tissues in plant and keep them firm and erect. The surrounding cells pushed
against each other creating support for the plant.
*. Other function of the turgor pressure :
a). To make some flowers open during the day and close at night.
b). Due to the changes in turgor of the guard cells, the stomata in the plant
opens and closes.
c). The changes in turgor of cells in the small swellings at the base of
the leaflets of mimosa plant causes them to fold when they are touched.
5. Define Active Transport!
-. Active Transport is the substances movement against a concentration gradient
which is from a lower concentration region to a higher concentration region;
and it is an energy-consuming process.
-. Example : It is important for root hair cells to absorb dissolved mineral salts and
for the small intestine cells to absorb glucose and amino acids.
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