Transport across a membrane

Transport across a membrane Transport across a membrane occurs by one of two opposite means, actively or passively. Active transport requires the cell to utilise cellular energy in the form of ATP, in order to employ protein pumps or engage in the activity of endo / exocytosis. Passive transport therefore occurs with no energy expenditure by the cell, where molecules exit or enter the cell using kinetic energy, or protein channels. To this effect passive transport encompasses, osmosis, diffusion of a solute across a membrane, facilitated diffusion and transport of an ion down an electrochemical gradient. The reasoning for this is outlined below. Intrinsic homeostasis at a cellular and molecular level is achieved when the cell is in an isotonic environment where the internal solute concentration of a cell is in equilibrium with the external, extra cellular environment, solute concentration and there is no net movement of water in any direction. A change in concentration of solute, initiates transport across the membrane in order to achieve equilibrium once again. The cell membrane is a structure designed in such a way to allow passage of molecules and ions in and out of the cell, to and from the extracellular fluid, whilst keeping essential components such as organelles and ribosomes within its boundary. It is comprised of a phospho lipid bi-layer, in which are embedded a variety of carrier and channel proteins. The lipid bi-layer acts as a barrier to molecules in both directions and the proteins allow entrance and exit of select molecules. (www.faculty.weber.edu/jclark1/mem%20 Permeability. PDF 25.11.09) Some chemicals will traverse the membrane, such as water, carbon dioxide, oxygen, small polar molecules and lipids and others such as ions, amino acids, large polar and macromolecules will not and the membrane is effectively selectively permeable. (www.staff.jccc.net/PDECELL/cells/transport.html 25.11.09) The most basic category of passive transport is that of diffusion of a solute across a membrane. Molecules that move across the membrane in this manner are more soluble in oil than in water and hence effortlessly ‘dissolve in and spontaneously cross the non polar lipid core of the membrane bi layer Examples of these molecules are steroid hormones, Oxygen and Carbon Dioxide (www. Biologyreference.com/Ma-MO/membrane-Transport.html 26.11.09) during the process of diffusion, ‘molecules move from an area of high concentration to an area of low concentration down the concentration gradient in order to achieve equilibrium. This is achieved by kinetic energy of the molecules whi ch are in Brownian motion. An increase in temperature causes the rate of diffusion to increase causing equilibrium to be achieved more quickly as kinetic energy increases. Size and type of molecule also has a bearing on the rate as the smaller the molecule the faster it will diffuse. Osmosis is purely ‘the diffusion of water molecules across a partially permeable membrane from a region of higher water potential to an area of lower water potential'(www.biologymad.com/resources-getting in and out of cells 25.11.09) In an isotonic surrounding there is no net movement of water molecules in either direction as there is no concentration gradient, however in a hypertonic solution where the concentration of solutes is higher and hence the water potential is more negative than the cell, water molecules from within the cell will move down the ‘water potential gradient to the extracellular fluid in order to achieve equilibrium. This can be shown in laboratory conditions by placing red blood cells in a hypertonic solution and observing them. Over time the cells will crenate as the water molecules exit the cell. Similarly if cells are in a hypotonic solution where the concentration of solutes is lower, the water potential is higher and hence the cells now have a more negative water potential and water will be taken into the cell by osmosis down the water potential gradient. Red blood cells left in a hypotonic solution and observed will show nothing under the microscope over time, as the cells eventually undergo cytolysis. (www.biologymad.com/resources-getting in and out of cells 25.11.09). Unfortunately most molecules cannot cross the membrane by straightforward diffusion alone as they are either too large, insoluble in lipid or they carry a charge which is repelled by the surface of the membrane. They therefore undergo facilitated diffusion, a mechanism by which passive transport still occurs without energy expenditure of the cell, but where the molecules are assisted across by groups of proteins inherent to the membrane. Facilitated diffusion still occurs down the concentration gradient but is specific to the molecule being facilitated. A carrier protein is specific to a particular molecule or class of molecules,(www.users.rcn.com/jkimball.ma.ulyranet/biologypages/d/diffusion.html#facilitated 26.11.09) where the molecule binds to the protein which in turn changes shape to enable the molecule to cross the membrane. An example of this being the transport of glucose into the cell. Once inside the cell glucose phosphate is manufactured for which there is no carrier prote in and hence glucose cannot pass back out of the cell. In this case equilibrium will never be reached. . (www.biologymad.com/resources-getting in and out of cells 25.11.09). In the case of transport of an ion down the electrochemical gradient, Ions transit from an area of high concentration to an area of low concentration again through facilitated diffusion with the aid of intrinsic proteins called ion channels. Without these channels charged molecules such as K+ Na+ would be repelled by the charge on the membrane. Transmembrane channels that allow facilitated diffusion, can be permanently open, or can be closed and opened as in neurones, and as such are known as ‘gated, they open or close in reaction to a ligand, a signalling molecule which can be either extracellular or intracellular. It is the gated mechanism that allows a nerve impulse to pass along a neurone. Sometimes however it is necessary for cells to transport molecules against the gradient by the use of carrier proteins, known as protein pumps. They are akin to those of facilitated diffusion, except they are working against the gradient and therefore energy in the form of ATP is expended by the cell in the doing so. This process is known as Active Transport. In all the cases outlined above the objective of passive transport has been to transport molecules across the semi permeable membrane down a concentration gradient, without expenditure of energy to the cell, and, passive transport can be demonstrated by diffusion of a solute, osmosis, facilitated diffusion and transport of an ion down an electrochemical gradient.

Booker T. Washingtons Influence on Historically Black Colleges Essays

BOOKER T. WASHINGTON: THE AMBIGUITY OF INFLUENCE ABSTRACT My paper will discuss the continuing influence of Booker T. Washington's writings on historically black colleges. While my paper will focus on the ways in which the historically black college continues to adhere to the model provided by Washington, it will also explore the ways in which it diverges from the early Hampton-Tuskegee ideal. According to James D. Anderson in The Education of Blacks in the South, both contemporary observers and later historians have portrayed the white south as taking a monolithic view of black education. However, many secondary schools in the south did not emphasize the kind of industrial education advocated by Washington. In the same manner, the historically black college no longer places the emphasis on vocational training it did at one time. However, there are still advocates for Washington's model although the training under discussion is in technical fields. Washington's influence can also be found in the importance often placed on action in hi storically black colleges, such as mine, which can undermine attempts on the part of faculty to pursue a life of the mind. At the same time, stimulating new influences emerging from African-American studies are changing and enhancing the campus culture enriching both students and faculty. My paper will conclude by considering the influence of honors programs as well as multi-ethnic and multi-cultural student bodies and faculties on the future directions of the historically black college. INTRODUCTION The freedmen and women of the Ante-Bellum South had a thirst and hunger for knowledge known by few; often learning from another freedman who had just learned to read himself, freed... ... bonds to a past and to an American tradition erase all personal feelings of self-aggrandizement and intellectual pride, a place where the self encounters the struggle of America's past, a place where the soul grows deep like the rivers. WORKS CITED Anderson, James D. The Education of Blacks in the South, 1860-1935. Chapel Hill: U of North Carolina P, 1988. Du Bois, W. E. B. The Souls of Black Folk. 1903. New York: Penguin Books, 1989. Sims, Serbrenia J. Diversifying Historically Black Colleges and Universities: A New Higher Education Paradigm. Westport: Greenwood P, 1994. Washington, Booker T. A Sunday Evening Talk. Tuskegee Institute, Alabama. 15. Jan. 1911. Washington, Booker T. Up From Slavery. 1901. New York: Doubleday & Co., 1963. Willie, Charles V., and Edmonds, Ronald R. Black Colleges in America. New York: Teachers College Press, 1978.

Automobile Industry, India Automobile Industry Essay

Following India’s growing openness, the arrival of new and existing models, easy availability of finance at relatively low rate of interest and price discounts offered by the dealers and manufacturers all have stirred the demand for vehicles and a strong growth of the Indian automobile industry. The data obtained from ministry of commerce and industry, shows high growth obtained since 2001- 02 in automobile production continuing in the first three quarters of the 2004-05. Annual growth was 16. 0 per cent in April-December, 2004; the growth rate in 2003-04 was 15. 1 per cent The automobile industry grew at a compound annual growth rate (CAGR) of 22 per cent between 1992 and 1997. With investment exceeding Rs. 50,000 crore, the turnover of the automobile industry exceeded Rs. 59,518 crore in 2002-03. Including turnover of the auto-component sector, the automotive industry’s turnover, which was above Rs. 84,000 crore in 2002-03, is estimated to have exceeded Rs. 1,00,000 crore ( USD 22. 74 billion) in 2003-04. Automobile Dealers Network in India In terms of Car dealer networks and authorized service stations, Maruti leads the pack with Dealer networks and workshops across the country. The other leading automobile manufactures are also trying to cope up and are opening their service stations and dealer workshops in all the metros and major cities of the country. Dealers offer varying kind of discount of finances who in tern pass it on to the customers in the form of reduced interest rates. Major Manufacturers in Automobile Industry Maruti Udyog Ltd. General Motors India Ford India Ltd. Eicher Motors Bajaj Auto Daewoo Motors India Hero Motors Hindustan Motors Hyundai Motor India Ltd. Royal Enfield Motors Telco TVS Motors DC Designs Swaraj Mazda Ltd Government has liberalized the norms for foreign investment and import of technology and that appears to have benefited the automobile sector. The production of total vehicles increased from 4. 2 million in 1998- 99 to 7. 3 million in 2003-04. It is likely that the production of such vehicles will exceed 10 million in the next couple of years. The industry has adopted the global standards and this was manifested in the increasing exports of the sector. After a temporary slump during 1998- 99 and 1999-00, such exports registered robust growth rates of well over 50 per cent in 2002-03 and 2003-04 each to exceed two and- a-half times the export figure for 2001-02. Automobile Export Numbers Category1998-991998-99Passenger Car25468121478Multi Utility Vehicles26543892Commercial Vehicles1010819931Two Wheelers100002256765Three Wheelers2113851535Percentage Growth-16. 632. 8 THE KEY FACTORS BEHIND THIS UPSWING Sales incentives, introduction of new models as well as variants coupled with easy availability of low cost finance with comfortable repayment options continued to drive demand and sales of automobiles during the first two quarters of the current year. The risk of an increase in the interest rates, the impact of delayed monsoons on rural demand, and increase in the costs of inputs such as steel are the key concerns for the players in the industry. As the players continue to introduce new models and variants, the competition may intensify further. The ability of the players to contain costs and focus on exports will be critical for the performance of their respective companies. The auto component sector has also posted significant growth of 20 per cent in 2003-04, to achieve a sales turnover of Rs. 30,640 crore (US$ 6. 7 billion). Further, there is a potential for higher growth due to outsourcing activities by global automobiles giants. Today, this sector has emerged as another sunrise sector. EVEN GROWTH Opposing the belief that the growth in automobile industry has catered only to the top income-stratum of society, Growth of exports of 32. 8 % in the first three quarters of 2004-05, the fastest growth in volumes has come from commercial vehicles as against passenger cars. Between 1998-99 and 2003-04, output of commercial vehicles has grown 2. 8 times compared to the 2. 2 times increase in passenger cars. Furthermore, two-wheeler output continues to dominate the volume statistics of the sector. In 2003-04, for every passenger car turned out by the sector, there were 7 two-wheelers produced. In the two wheeler segment, there is a greater preference for motorcycles followed by scooters, with both production and domestic sales of motorcycles increasing at faster rates than for scooters in the current and previous years. However, mopeds have registered low or negative growth. Export growth rates have been high both for motorcycles and scooters.

The Mental Health Act By Charlie Gordon - 1001 Words

In 1959, the Mental Health Act was passed to stop the difference in mental hospital and other hospitals. Before this act mental illnesses were looked at differently. People with mental disabilities were put in asylums. Now the world sees that differently because we include them in everyday life. In Flowers for Algernon, Charlie Gordon experiences having a mental illness, and learns how to live a normal life after a life changing surgery. Charlie’s surgery changes his life for the rest of his life. Charlie Gordon lived in New York City at the age of 32 with a mental disability. He attend Beekman College Center for Retarded Adults to try to learn to read and write. His teacher, Miss Alice Kinnian, suggested him to take part in an†¦show more content†¦Donner, fire Charlie. He also learns the social skill love. He sees Miss Kinnian as his love, but she tells him that she is the only women in his life that he know well, and to go talk to other women. He eventually does this and finds interest in other women but they don t go very well. The Charlie before the surgery didn’t know much about his childhood, but the smarter Charlie had flashbacks of his childhood like how his mother used to love him but then didn’t and sent him away. One day he ventures to go see his father in his barber shop, but his father doesn’t recognize him and Charlie leaves without revealing who he is. Charlie then realizes that he needs to be put on the committee of this experimen t because he thinks he sees a flaw in the experiment which he later proves to be true. He proves that he will slowly fall back to the stage he was at before the operation. Just about right after he finishes this, Algernon dies and Charlie buries him in his backyard. Before he stops progressing and starts degressing he goes to visit his mother and sister. After regressing back to his old self, he goes to get his job back at the bakery. After seeing Alice again at the school, he thinks people feel sorry for him and goes to live in the Warren State Home. Charlie experiences drastic changes throughout the story. All of them are mentally due to the experimental operation he had. In the