Реферат: BioReport Essay Research Paper 1 Cellular TransportaOsmosisOsmosis

Bio-Report Essay, Research Paper

1.) Cellular Transport


Osmosis is the diffusion of water molecules across a differentially permeable membrane from a region where water molecules are more concentrated to one where they are less concentrated. The transport of water is simple the cell being selectively permeable will allow water through it until an equilibrium is reached and at that time water will flow both in and out of the cell maintaining the equilibrium. For example a red blood cell is placed into a isotonic solution which means both the solution and the cell have the same concentration the net movement of water is zero, water however does move freely in and out of the cell to maintain the balance.

b.Active Transport

In active transport a cell moves materials from an area of low concentration to an area of high concentration, this process is the opposite of osmosis or diffusion. Active transport requires energy because it is moving against the concentration gradient. In active transport the cell uses ATP to remove unwanted materials and to receive needed ones. For example a muscle cell wants potassium and wants to get rid of a sodium, the cell releases ATP to the pump proteins which results in the cell ejecting the sodium ion and at the same time another receptor cell accepts a potassium which is then released into the cell and the process is repeated until the cell is finished.

c.Facilitated Transport

In facilitated transport a molecule that cannot normally pass through into a cell use a carrier protein to gain access and exit. Basically this allows a cell to acquire molecules that cannot get through it+s selectively permeable membrane. For example a plant cell requires glucose and the glucose will not fit through the cell membrane. A carrier protein in the plasma membrane will accelerate the movement of the glucose and allow it into the cell.

2.)Tropic Levels and The Food Chain

a.One of the primary producers of this food chain, the aquatic plants and algae, get their energy from the sun and the soil, with this energy they make their own food and live.One of the primary consumers of the aquatic plants are the aquatic insects which get their energy from feeding off the plants in the lake.The secondary consumers in this lake are the many small fish which inhabit it, they receive their energy from feeding off the small insects. The head of the food chain in the lake are the lake trout which eat just about anything it can find including the smaller fish, it gets it+s energy from them.

b. The energy transfer between these tropic levels is incredibly efficient, the amount of energy on any given tropic level is balanced through the availability of the food on each of the levels. If there is an overpopulation somewhere it is quickly taken care of and the balance is restored.

c.Surprisingly the effects would not be that great because the snails that feed off of the toxic material would die off or adapt to it until it stopped, the lake trout would of course just find another food source until the balance was restored. Even if the effects of the toxin were great eventually a balance would be restored.

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