Diffusion and Osmosis Lab Report Example | Topics and Well Written Essays - 2500 words

Diffusion and Osmosis - Lab Report Example The cell and its extracellular environments are fluid in that concentrations of substances dissolved in it vary. Depending on varying concentration of the substances dissolved in water, be it extracellular or intracellular, dissolved substances or water move from one compartment to another directed by physical principles of gradients. To accomplish this, the cell utilizes the processes of osmosis and diffusion as appropriate. These phenomena can be visualized outside the cell by simulating these in vitro. Since cell membrane is a semipermeable membrane and exchanges occur through this, these experiments must utilize a construct of the semipermeable membrane that can be made with a commercially available dialysis tubing and bag. These membranes have microscopic pores through which small molecules like water can pass, but larger molecules, such as sugar cannot pass through them. Thus through this molecular net, solutions of different solute concentrations can be observed to pass in a m easurable fashion. This experiment has been designed to prove the hypothesis of the mechanisms of osmosis and diffusion through such a semipermeable membrane. Diffusion is defined as the movement of molecules from a site of higher concentration to that of a lower concentration. Technically speaking, this difference in concentration creates a concentration gradient, and the steepness of the gradient determines the rate of diffusion. In an attempt to find out the reason as to why it occurs, it can be attributed to a great deal of space between the molecules of all substances that are candidates for diffusion. Liquids have moderate intermolecular space. Moreover, all molecules are in a state of constant random movement so that they collide and intermingle. It is expected that in solids diffusion would occur slowly for tight packing of the molecules. Liquids and gases would diffuse freely because their molecules are spaced widely. Thus, it can be stated that any solute will tend to uniformly occupy the entire space available to it. This movement, known as diffusion, is due to the spontaneous Brownian random movement that all molecules experie nce. The net result of diffusion is the movement of substances according to their difference in concentrations, from regions of high concentration to regions of low concentration. Diffusion is an effective way for substances to move short distances. Diffusion across a membrane has no preferential direction; it can occur from the outside of the cell toward the inside or from the inside of the cell toward the outside. It is however determined the extend of permeability through a membrane, which in the case of a living cell is the protein-lipid-protein plasma membrane, and therefore, diffusion across the membrane usually implies that the diffusing solute enters the lipid bilayer to cross it, the solute's solubility in a lipid solvent compared with its solubility in water is important in determining its permeability through it. Hydrophilic substances, such as ions and sugars, do not interact well with the lipid component of the membrane, hence would diffuse across the membrane more slow ly. This is, however, not applicable in physical membrane such as a dialysis membrane (Campbell NA, Reece JB, Mitchell LG., 1999). If equal volumes of pure water and a strong sugar solution are taken, the pure water will have more water molecules and would have higher water concentration that a sugar

Client and Policy Failure Assignment Example | Topics and Well Written Essays - 250 words

Client and Policy Failure - Assignment Example By doing so; I will able to cater for the interests of my clients who are affected negatively by the policy on basements and city building codes. My responsibility is to assist clients obtain affordable housing that are safe and habitable, as opposed to expensive houses that lead to people living in the streets. Thus, the clients’ get affordable housing and the city remain free of homeless people. The action-forcing event that triggered the study was the numerous complaints made by New York residents, demanding that action to be taken concerning illegal and unsafe apartments. These individuals are taxpayers being forced out of their homes, and owners of basement apartments being asked to dismantle their rental units, as in the case of Rakha and Mahbub who were asked to pay a penalty of $1,200, after spending more than $4,000 upgrading a cellar apartment of their home in Queens. In addition, the supporters of legalization of basement apartments such as Jerilyn Perine, a former city housing commissioner, and current Executive Director of the research group Citizens Housing and Planning Council claim that the issue of basement housing and other illegal houses has to be dealt with, as well as the allowance of a better city planning strategies. This is in relation to the words uttered by the City Councilman Brad Lander who said he was outlining legislation in favor of the â€Å"a ccessory† housing units, and building code standards for them. The actual policy targeted for reform is the New York City Building or the Housing Maintenance Code, (ARTICLE 5- Occupancy of Cellars and Basements). That states that basements, cellars, and â€Å"granny flats,† should not be rented or occupied due to health and safety measures. What policy options exist for Assistant Secretary of State for Consular Affairs Janice L. Jacobs to decrease employment visa fraud committed by U.S. based high-tech companies in response to the recent discovery of visa fraud committed by