Botany-Passive Transport Answers Essay
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Substances necessary for normal growth and development of plants must continually be transported into cells while metabolic wastes must be eliminated so that they won’t accumulate inside the cells. For instance, water as well as mineral salts from the soil solution enter root cells while carbon dioxide and oxygen through tiny pores known as stomata in leaves and lenticels in stem. Excess oxygen not utilized during cell respiration as well as oxygen produced during photosynthesis is released to the atmosphere.
In most cases, movement of these substances is along a concentration gradient, that is, from regions of greater concentration to regions of less concentration. Such type of transport is known as passive transport.
Diffusion is a type of transport which is concerned with the movement of solute particles. Aside from concentration gradient, factors affecting the rate of diffusion include the temperature, size of diffusing molecules and presence of other molecules aside from the diffusing one. Osmosis, on the other hand, is another type of passive transport, which is involved in the movement of solvent (e.g. water) through a semi-permeable membrane. In osmosis, the presence of a differentially permeable membrane as well as differences in the concentration of the medium and the intracellular substance (i.e. cell sap) are factors to consider in determining the direction of water flow. (madel, dito gawa k ng visuals na puede,.. kung aong maisip mo di ko nga alam kung ano puede ndin ilgay …. Ano kaya gagamitin ntin? Naka-acetate oh sa manila paper kaw n bhala..;)
Now the walls of these cells are made of a stuff a bit like a really fine netting that will let water through but not salt (a partially permiable membrane). Now water and salt prefer being mixed together than seperated, and water will move through the cell wall towards whichever side is the saltiest, this is called osmosis.
This means that because outside is saltier the water leaves the cells, so the cells empty, and like a half full bag of water, go all floppy so the whole lettuce leaf goes floppy
Now if you put the leaf in fresh water there are more salts in the leaf than in the water, so water will move back into the cells making them blow up like balloons again and become all strong and rigid.
So if you have some old limp Lettuce soaking it in water for a while for a while will make it go crisp again.
-The leaf in the salt water would be dehydrated, as its internal osmotic pressure would make water from the leaf seep through the cellular membranes. -it’s osmosis. the cells in the leaf are permeable to water but not salt,so if you immerse the leaf in salt water the cell will absorb water trying to balance the osmotic pressure .if you put the leaf in fresh water the cells will dump water,the salt water will cause the cells to absorb too much water and they will burst,the fresh water leaf will dehydrate and wrinkle,i think i got it right but don’t quote me. -Your talking about tonicity, the salt solution is hypertonic and would pull fluid from the plasmodesmata in the plant cells…the plain water being relatively isotonic would have little loss of fluid depending on where you live in the country and if you used tap water or bottled. Its the same concept of cellular dehydration and water toxicity in human cells.