Research paper Example | Topics and Well Written Essays - 1500 words

Research Paper Example Consequently, the innocent young girl encounters an enormous wolf in the woods in the process of delivering food to her grandmother. Thus, the young girl innocently informs the wolf of her destination. The wolf then goes ahead and swallows the girl’s grandmother. Unsatisfied, the evil wolf decides to wait for the young girl in the pretense of her grandmother. However, upon arrival the young girl notices some strange behaviors concerning her grandmother. First, her voice was extremely deep. In addition, her eyes and hands were also immensely enormous. Moreover, her mouth was also enormous. However, before the little girl could unravel the happenings the wolf pounced on her and swallowed her (Zipes 4). With his tummy full, the wolf fell into a deep sleep. However, in his deep sleep a stranger comes to the rescue of the duo. He cuts the wolf’s belly open with a saw to the delight of Little Red Riding Hood and her grandmother who emerge from the wolf’s belly unscathe d. Therefore, in order to teach the evil wolf a lesson the trio fills its belly with stones. Eventually, when the wolf wakes up he decides to run away, however, the stones weigh him down. Consequently, he collapses and dies. Therefore, it is clear that the tale attempts to outline the dangers of the enormous forest. In comparison with forest, the village offers a safe home as opposed to the former. Therefore, the tale was aimed at checking little children from engaging in dangerous practices since they could end up being harmed. COMPARISON WITH OTHER TALES Other tales such as Peter and the Wolf or The Wolf and the Seven Young Kids also employ a similar thematic footing. In both cases, the tales paint a thematic scenario in which an individual emerges unscathed from the belly of an evil wolf. As such, this thematic setting has been embraced by other numerous tales (Meidell 175). This overwhelming semblance to other fairy tales can be attributed to the origin of the tale reason being that the tale embraces a medieval bias that was popular in the ancient times. This similarity can also be associated with the moral lessons learnt from the tale. HISTORY OF LITTLE RED RIDING HOOD TALE Little Red Riding Hood has its origin rooted in various versions of the story in Europe. Consequently, its original versions date back to the 17th century (Iona and Peter 93). However, the tale was also told in both Italy and France in the fourteenth century. Consequently, this version was referred to as The False Grandmother. Therefore, this implies that the title of the tale varied from one region to another. As such, the original versions significantly differ from the present day versions (Tatar 17). For instance, the antagonist of the story needs not necessarily be a wolf. This implies that in other versions of the tale the antagonist is presented as a different character. For instance, an ogre is employed as an antagonist instead of a wolf. Other manuscripts also depict the antago nist in the form of a dragon. Nevertheless, the antagonist is depicted as a wolf in most cases. Since the tale is mainly meant for young audiences, the depiction of the antagonist as a wolf enables the audiences to easily associate and relate with the tale while appreciating its message. Consequently, depiction of the antagonist as an ogre may be effective for African audiences. However, in all these versions, the antagonist is depicted as an enormous and dangerous being. Moreover, the antagonist is

Business administration - Program Capstone Essay

Business administration - Program Capstone - Essay Example Moreover, a manager must specify objectives and prioritize interests, values, concerns and aspirations. Also a manager, who is aware of both short-term and long-term implications of a decision and have a 360 degree approach, makes better decisions (George, 2000). In order to achieve desirable results and better decision making, a manager must identify the purpose of decision and clarify all the uncertainties involved. The amount of risk that a situation at hand can tolerate must be carefully evaluated. Multiple ideas must be generated and a manager should not adopt a particular perspective, desisting a multidimensional approach of making better decisions. Perhaps the most crucial aspect of making better decisions is reviewing the steps and looking for the implications of it in order to revise them and take corrective actions. In the realm of decision making, assumptions are accepted cause and effect relationships that provides basis for actions and create useful what if scenarios to simulate different realities or possible situations (Facione,2007). However, they can be dangerous when accepted as realities without proper investigations. With respect to assumptions, the firm I worked with had its own perceptions of issues.

Ethics and Morality in the Health Professions Essay

Ethics and Morality in the Health Professions - Essay Example If at all God created every creature, then why should one think of taking his or her life away. It would be quite unethical in my career to leave such an individual to die when I knew in real sense that he or she was going to die. The only way that one could tell if someone else has feelings for suicide, could be through a conversation where he or she will confess such feelings. It was the right step undertaken by a patient who required suicidal assistance to approach you Dr. Deborah. It is quite true that a suicidal person who locks him or herself away tends to feel isolation and for that matter, they may end up attempting suicide without the knowledge of his or her friends and relatives. If at all Dr. Brody you would put yourself in the patient’s shoe, then you would not imagine that someone wishes you to take your life away. In most countries in the west, suicide has significantly shown that it is the foremost cause of death (Gutheil 29). These countries spend anonymous amo unt of money in maintenance of safety on roads but unaware on suicide and its prevention. It is the best option for a country to engage into campaigns on choices to make good life. A person who wants to attempt suicide or has feelings or thoughts of suicide, it is then quite evident that such individuals have symptoms to indicate that they can no more cope up with life. It is repeatedly as a result of series of events or cases that make somebody overwhelmed in distress or trauma. There is no doubt that this patient wanted you to be available in order to listen to him or her and feel about what he or she could be experiencing in life. A problem talked about in my view, sometimes creates a road map towards fundamental solutions. All doctors and even nurses for that matter have no substantial grounds to ignore their patients who request for assistance in suicide. It could be quite unethical if we rather allowed and assist patients to die. When anyone demands for help to die, such a req uest should enhance discussions to ascertain the reasoning of the patient through needs assessment with no grounds of judgment. Therefore Dr. Deborah, it would be my advice that you should not hesitate to assist. Acknowledge this request and oppose the inclination to abandon or ignore the dialogue. Listen to the patient and even more and establish a contract of no-suicide. Ask the patient to make a promise that he or she will eradicate such feelings of suicide. Such issues should be taken seriously to extend that if the patient appears acutely suicidal; endorse him or her under care in the hospital department of emergency. It would be also important to seek opinions from psychologists, counselors and psychiatrists. It is a question that most doctors should continuously ask themselves why people attempt suicide. People who want to avoid emotional pain that is unbearable normally result into suicide (Gutheil 40-42). It is therefore a task ahead of you Dr. Debora Brody to help your pat ient look for better choices that will enable him or her to think critically and analyze every situation in life. Why I would give such an advice to Dr. Brody is a decision that I fundamentally consider. I believe that life is such a precious thing that one should be neither denied nor think of taking it away. Suicide can not be the last option because death does not solve our worst experiences. One would think that it would be the end of our pains. I would not deny that painful life ends at the grave but

Reno v. American Civil Liberties Union, 521 U.S. 844 (1997) Essay

Reno v. American Civil Liberties Union, 521 U.S. 844 (1997) - Essay Example The CDA provisions were in tandem with Christian faith and the Holy bible which deplores immorality. The book of 1Thessalonians 4:3 states,† For this is the will of God, your sanctification; that is, that you abstain from sexual immorality." The Bible also states in the book of Proverbs 29:17, â€Å"Correct your son and he will give you comfort; He will also delight your soul.† This act sought to safeguard upbringing of children by shielding them from a filthy society that threatens corrupt their morality. However, in the case of â€Å"Reno vs. American Civil Liberties Union,† the court of Supreme upheld a previous lower court decision that the CDA violated two existing provisions of the constitution. The CDA act violated the first amendment that provided freedom of speech. The CDA was found also violating the Fifth Amendment by virtue of vagueness of its words such as â€Å"indecent â€Å"and â€Å"patently offensive† (Law.cornell.edu, 2014). The judges final ruling resonates with an incidence in the Bible where Jesus disregarded Mosaic Law in order to protect a more fundamental right in the book of John 8:7-8 where he saved an adulterous woman from a mob that wanted to stone her, as required by the Mosaic Law. â€Å"He, who is without sin among you, let him be the first to throw a stone at her and when they heard it, they began to go out one by one, beginning with the older ones...† Justice John Paul Steven recognized the fact that the government had the responsibility to protect minors from sexually explicit materials but expressed his concern that the provisions unnecessarily suppressed the right to provide information to adults which could be educative. For instance a discussion on birth Control practices. The court was also concerned with the criterion used to define indecent materials or communication. The court argued that CDA â€Å"community standards† criterion implied that other nation- wide internet communication would be

The Many Issues Working Parents Face Essay Example for Free

The Many Issues Working Parents Face Essay Working parents may consider work to be either a blessing or a curse. Most people agree that without work there is no way to support oneself or a family. Both parents are forced to work because they want their children to experience â€Å"the good life.† However, on their road to success, working parents have to sacrifice several other things. In addition to a lack of family or leisure time, a person’s job also creates a lot of stress. Work can be the highway to success. However, hectic schedules caused by long hours of work can lead to negative changes in one’s personal life. Marilyn Gardner talks about a cop whose work hours are messed up. She states that Mr. Fulgham â€Å"works twelve-hour shifts which rotate between days and nights† and eats breakfast when his family is normally eating lunch. He gets almost no time with his family. When he gets a chance to spend time with his family, it causes the schedule of his family to get messed up too (Gardner 235-38). De Graaf, a journalist for the New York Times, states that â€Å"(u)ntil the current recession, Americans were working some of the longest hours in the industrial world.† Long hours at work lead to lesser time with family. For example, in â€Å"My Mother, Her Career, My Questions,† Palmer has a friend whose mother hardly spent any time with her. Being a doctor and working long hours, the mother was so tired when she came back home that she had to â€Å"force hers elf to play† with her kids (Palmer 244). This shows how work can have a negative impact of the person’s relationships with his/her family. Even parents feel guilty about not being able to spend enough time with family. They admit that the longer they work, the lesser time they spend with their kids (Seligson). It is said that people who work longer hours are more likely to get a divorce due to the lack of togetherness. The main point of being a â€Å"family† is that the members of the family have to be together and enjoy each other’s company. However, parents that work weird schedules or extremely long hours fail to spend enough time with their family. This loosens relationships and can even tear apart families. Thus, there has to be a balance between work time and family time. Parents are always aiming to work those extra hours to get more work done, but they do not realize that  they are missing out on their children’s lives. Additionally, working parents need to know that too much work can also cause Another negative effect of working long hours is the stress it causes. When there isn’t enough time to complete a certain project at work, a person works overtime to finish it. These long hours can mess up a person’s daily schedule. Anger, exhaustion and stress are some of the many negative effects long hours have on an individual (Gillian). Audrey Gillian, a journalist for The Guardian, feels that Ronald Regan was wrong when he said â€Å"hard work never killed anyone.† The health issues caused by working long hours can eventually lead to death. In addition to that, in â€Å"The Case for Staying at Home,† Claudia Wallis talks about how women have to work both at their workplace and at home which creates more stress and exhaustion. In â€Å"Serving in Florida† Barbara juggled two different jobs. With the minimum wage she got, she could hardly afford to pay her rent (Ehrenreich 179-186). She started working longer hours to get more money. Although she tried fighting till the end, she had to finally give up both her jobs because she was working all day and couldn’t seem to make ends meet (Ehrenreich 186). It seems like people have to choose between life and work. After coming back from a day of hard work, one would usually opt to take a break and just rest. However, women are expected to come home and attend to the family’s needs. She has to cook, clean and basically keep her family happy (Wallis 240). This causes the person to be stressed out and fatigued. People need to realize that it is fine to take a break from work once in a while. A person’s body has a certain limit for everything. When a person goes beyond that limit, the human body reacts and this causes stress and other health related issues. Stress leads to fights which lead to broken relationships. Are you ready to forget about family and only focus on your career? Most would say that there needs to be balance so that one can be successful at work and at the same time, maintain good relationships with his/her family. All in all, work may have a positive effect on our lives, but in excess it can ruin a person’s life and even break up families. Work can also make a person weary and tired. If you are in surgery, would you prefer a well rested doctor to operate on you or one who has been working the whole day with no break? I would surely opt for the rested one to make sure nothing would go wrong. People need to maintain a work-life balance so that the effects of work  don’t cause their life any harm. Works Cited de Graaf, John. Less Work, More Life. The Progressive Sept. 2010: 22+. Gale Opposing Viewpoints In Context. Web. 10 Dec. 2012. Ehrenreich, Barbara. Serving in Florida. 2001. The Language of Composition: Reading, Writing, Rhetoric. Boston: Bedford, 2008. 179-86. Print. Gardner, Marilyn. More Working Parents Play Beat the Clock. The Language of Composition: Reading, Writing, Rhetoric. Boston: Bedford/St. Martins, 2008. 235-38. Print. Gillan, Audrey. Work until You Drop: How the Long-hours Culture Is Killing Us. The Guardian. Guardian News and Media, 20 Aug. 2005. Web. 06 Dec. 2012. Palmer, Kimberly. My Mother, Myself, Her Career, My Questions. The Language of Composition: Reading, Writing, Rhetoric. Boston: Bedford/St. Martins, 2008. 243-45. Print. Seligson, Hannah. When the Work-Life Scales Are Unequal. The New York Times. The New York Times, 02 Sept. 2012. Web. 10 Dec. 2012. Wallis, Claudia. The Case for Staying at Home. 2006. The Language of Composition: Reading, Writing, Rhetoric. Bedford, Freeman Worth Pub., 2008. 240-41. Print.

Cost Leadership Strategy For Tune Hotels Tourism Essay

Cost Leadership Strategy For Tune Hotels Tourism Essay As a business development manager of Tune hotel, I have been requested to propose and justify the implementation of an overall cost leadership strategy for Tune hotels.com. this proposal is consists of preparing a strategic service vision for Tune hotels.com by taking few aspects as a consideration into account, such as the target market segment, service concept, operating strategy and also the service delivery system as well. Besides that, I have been asked to identify what are the service dimensions in setting the benchmark for service qualifiers, service winners and service losers as well. Hotel overview Air Asia is a low cost carrier (LCC) airline, with the image of making flying feasible for everybody, where it is well known for the largest low fare and no frills airline, and Tune hotel is one of another luminous thought invented by the air Asias Chief Executive Officer (CEO) and also the founder of Air Asia as well, Datuk Tony Fernandes. Tune hotels have open its first no frills hotel branch in Jalan Tuanku Abdul Rahman,Kuala Lumpur on 9th april 2007. Tune Hotel is currently operating in places such as Malaysia, Downtown Penang, Kota Damansara, Kuala Lumpur, KLIA LCCT Airport, Johor, Kuching, Kota Kinabalu, Indonesia and United Kingdom and London as well. Question 1 Target market segment As in the context of a business, target market segment is an essential element which is needed to be considered and it is important in facilitating and directing the business path in the market. Target market segment, which is targeting the audience, is very important to sustain the survival of a business or industry as well. Tune hotel which has been categorized under the service industry and it can be considered as the market leader in the no frills budget hotel in Malaysia and South East Asia. Tune hotel has implemented a creative and innovative concept to be used in Malaysia, and they differ from their competitors since no any hotel or company has claims to be in the same market segment. Tune hotel has used the geographic segmentation dimensions to influence the market opportunity, for instance, tune hotel at Kuala Lumpur, Jalan Tuanku Abdul Rahman, which is known as the budget hotel which has the similar concept of no frills Air Asia Airlines,tune hotel also adapt the same concept where it is also the first no frills hotel in Asia as well. Tune hotel Kuala Lumpur are strategically located at the central of Kuala Lumpur in Jalan Tuanku Abdul Rahman, whereby it is close to major shopping, food and beverage outlets and entertainment areas. Moreover, the location is also convenient and facilities such as LRT and bused as well. (Anonmous, n.d) Swot analysis of tune hotel Strength Tune hotel has a great strength whereby they have a reward system to those customers who have done an advance booking service through internet with them. By introducing this system, tune hotel will be able to attract more customers and maintain those loyal customers in future as well. Besides that, Tune hotel have a great central location with facilities such as LRT and buses and it is nearby shopping areas, entertainment areas, and food and beverage areas as well. This attracts and encourages those customers, especially foreigners to choose Tune hotel as well. Moreover, Tune hotel are attractive with their pricing strategies as well, in situation where most of the Air Asia customers are those tune hotels loyal customers. Weakness Tune hotel has a very limited number of customers in the region who are conscious of the Tune hotel. This could be one of the weaknesses faced by Tune hotel. Tune hotel should be able to work on their advertising method and emphasis more on their service provided. Opportunity In order to gain the competitive market and be the first market leader in service industry, Tune hotel can be able to attract more customers by improving their marketing strategy effectively to gain the customers satisfaction and their support as well in future. Threat Tune hotel receives a high competition in the service industry since it has been unique in the industry. High Competition among competitors is one the biggest threat to tune hotel to sustain in the market in the future. Outsourcing is also one of the threat to Tune Hotel since other Hotels do provide facilities which tune Hotel doesnt provide, for instance other hotels have basis necessities of customer such as the boiler, drinking water and many more, meanwhile Tune hotel does not provide all this. Service concept Source: http://www.xm-msia.com/xm/tunehotels/facilities.asp Tune hotel is unique in providing their service, compared to their competitors, and they operate a limited service concept, where they only offer single and double room for its customers. They have 5 star beds provided in each rooms feature high quality spring mattress beds with basic needs such as pillows, pillowcase and bed sheets. Each of the room consists of attached private bathrooms together with heated power showers with the minimal room rates. Tune hotel are have a central and convenient and strategic location which is nearby to shopping areas, ATM services to withdrawal purposes, food and beverage such as kopitiam outlets and entertainment as well. Moreover, Tune hotel has 24-hour security facilities as well whereby it is secure and safe to be in the surroundings of the hotel. Operating strategy Tune hotel makes use of the outsourcing as their operating strategy to save the operation cost and to improve and get better output and efficiency of the hotel. For instance, Tune Hotel in Kuala Lumpur, the maintenance, Kopitiam, 7 eleven which is available for 24 hours, money changer kiosk, fast food outlets such as Subway, and CIMB ATM and bureau the change are certainly part of outsourcing. By implementing this operating strategy effectively, Tune Hotel have be able to save a huge amount of their cost and this eventually helped Tune Hotel to improve on better production and productivity effectively and efficiently of their hotel. ( Batcha, 2007). Service delivery system Source: http://www.scribd.com/doc/4089502/Tune-Hotel The service delivery system in Tune Hotel is overwhelming, and core and supplementary services provided are identified through the flower of service model. The service are divided into 2 main sections, where the information, order taking, billing and payment are categorized under the facilitating services, meanwhile consultation, housekeeping, hospitality and exception are categorized under the second section named as enhancing services. TUNE HOTELS STAKEHOLDERS Source: http://www.xm-msia.com/xm/tunehotels/about_us_3.asp Tune hotels sdn.bhd is 40% owned by Datuk Tony Fernandes, 30% by Dato Kamarudin Meranun, 25% by Dennis Melka and the rest 5% by Tune Strategic Investments Limited. Tune Ventures Sdn Bhd owns 72.19% stake in tune hotels, followed by Dato Kalimullah Hassan which now the chairman of ECM avenue which is one of the listed Malaysian investment bank owns 12.03% stake in tune hotels, Lim Kian Onn the chairman of ECM avenue, also owns the same percentage as Dato Kalimullah Hassan 12.03%, and lastly followed by tune hotels employee holding sdn bhd where the company is formely owned by the key employees of tune hotel owns 3.75% stake in tune hotels as well. Question 2 Service qualifiers Tune hotel is classified to be the service qualifier since it is providing a good service which meets the requirements of a consumer. For instance, tune hotel has a clean environment around, whereby they provide housekeeping services to make sure the consumers feels safe and clean with the surrounding environment. Moreover, Tune hotel are concerned with the safety as well, where they have the 24 hour security system applied, whereby they uses electronic key card to access into rooms, CCTV cameras services, round- the- clock on duty reception staff and no access to the main lobby without a keycard pass midnight.(anonymous, 2007) Moreover, tune hotel also has introduced tune hotel insurance only in Malaysia, and said to be globally soon. Those insurance are not only responsible for the lost of travel documents, but also has take the responsibilities of being cautious of guests personal accident, medical expenses and also delayed check in as well.(anonymous, n.d). Service winners Service winners are those competitive dimensions used to make the final choice among competitors, for instance is the price. The pricing strategy of Tune hotel is from the range of RM 9.90. Tune hotels price will be different during peak seasons, promotion seasons and also a different price range for the advance booking as well. Service loser When tune hotel fails to deliver the needs and wants of the customer, they might entitle to be the service loser. Service loser occurs when there is a failure to meet the expectations of what customer actually wants. Tune hotel should be able to implement new marketing strategy as Tune Hotel is having a high competition among its competitors which is a threat to them. Question 3 Porters generic strategies Source: http://www.quickmba.com/strategy/generic.shtml Tune hotel has adopt the cost leadership strategy overall. This cost leadership strategy mainly emphasis on the low cost producer in the industry. Setting price low sometimes might influence the way of thinking of a customer, where low price may give a negative perception of the quality and the brand image of the company itself. For instance, there are not many out there are aware about Tune hotel and its services, since it is new in the market. This is mainly because the strategy used to representation about Tune hotel is done ineffectively. Tune hotel should come up with an effective strategy to expose their brand name by having advertisement about its service and facilities provided to attract not only the Air Asias customers, but also to the locals and foreigners who travel frequently. Placing Tune hotel in a strategic location with the lower price is valuable, but it should also be a place where customers feel flexible and convenient with the environment as well. Tune hotel in Kuala Lumpur, Jalan Tuanku Abdul Rahman where it is a location which is popular with prohibited immigrations and place where they gather together. The place is nearer to the place where most of the time it is famous with prostitution, drugs and offense are indivisible. This might not guarantee the safety at times and it could be one of the main problem customers will have a choice to choose other hotels as their choice. Tune hotel can improve this by making a deep study and research about those place and plan the location as well to avoid those circumstances occur. Moreover, Tune hotel has limited services where they dont provide the basis necessities such as boiler, drinking water and so on. Tune hotel save cost on this, but yet it should not be limited in providing the services since its known as the budget hotel. Tune hotel can improve on their service provided to enhance the satisfaction of the customers and maintain its competitive advantage than its competitors. Conclusion Overall, Tune hotel has been taking the efforts to reach the audience by implementing the no frills concept hotel. Since it is still new in the market, Tune hotel should implement new ideas to expose its brand name and win the local consumers perception as well to adopt their name as well.

Virus-host Receptor Interactions in Biology

Virus-host Receptor Interactions in Biology Abstract Viruses are obligate intracellular parasites and, as such, must penetrate a suitable host cell in order to replicate their genomes and disseminate. Most viruses are limited to a specific set of cells or tissues in which they can successfully replicate, and this may be in one or more particular species. When viruses are able to bind a variety of cells, the pathogenesis and overall effect on the organism may differ. The main determinants of viral tropism differ between different virus families, but in order to take the first, and arguably most important step, in the infection of a host cell, the virus must attach via specific interactions between cell surface molecules and viral proteins. Enveloped viruses usually have proteins embedded in their envelope, assembled at the host cell surface prior to budding. In the case of some viruses (such as HIV-1), these may even consist of cellular proteins from the host cell itself. Non- enveloped viruses are usually internalized in some way and uncoated in an endosome in a pH-dependant manner. Many viruses require a number of cell surface receptors for cell entry, and it is this combination, added to other factors such as replication proteins, that determine whether or not a virus can penetrate and replicated within a certain cell. Introduction As obligate intracellular parasites, the life cycle of viruses depends on an intracellular replication phase and they are thus dependant on living cells. The first essential interaction a virus makes with a host cell is with a cell-surface receptor. A viral receptor may be defined as any cell surface component that mediates recognition of a cell and facilitates entry of the virus and subsequent infection. Receptors serve to ensure infection by overcoming repulsion between the virus and cell. (Baranowski, Flint, Jindrak, modern virol) Cellular receptors are generally proteins, although other types of receptor, such as carbohydrates, may be used (see table 1). These molecules are essential components of the cell or extracellular matrix and functions may include cell adhesion, signalling e.g. chemokine and growth factor receptors. (Baranowski 2003) While some viruses require only one receptor, binding to one cellular receptor alone may not be sufficient for initiation of infection for other viruses. Viruses may bind two or more receptors in sequence in order to initiate endocytosis or membrane fusion. For some viruses, the first contact with a cell is through a low-affinity interaction with a ubiquitous molecule, which allows the primary receptor-virus interaction to take place. The primary receptor is generally unique to certain cells and therefore partly defines the tropism of that particular virus, as cells are rendered susceptible to infection by a certain virus if the receptor required for attachment and entry is present. The primary attachment receptor may induce a conformational change in the viral envelope protein bound, to induce further interaction with the cell. (Modern Virology) A further interaction may then be required to initiate infection, performed by a coreceptor.The definition of the term coreceptor may sometimes be ambiguous, but generally, it is taken to be the molecule that induces fusion or penetration of a cell. This may be a further determinant of tropism, for example the interaction of HIV-1 Virus entry into a cell is the first step in the life0cycle of a virus; various mechanisms of viral cell enrty are shown in figure 1. The mechanism of entry varies between viruses, but all begin with the binding of a cellular receptor by a viral protein. Binding of a cellular receptor may induce endocytosis or formation of an endosome, the acidic environment of which induces uncoating; this may be dependent upon cellular proteins clathrin or caveolin. Enveloped viruses may require an acidic environment that will induce conformational changes in envelope proteins required to induce membrane fusion, while others, including the measles and HIV viruses, can fuse directly with the plasma membrane at neutral pH. (Baranowski) Fusion at the plasma membrane releases the nucelocapsid into the cytoplasm, where the virus can make its way to the nucleus or begin replication in the cytoplasm. The differences in these entry pathways are due to the nature of the molecular interactions between the vi ral components and target-cell receptors, for example, viruses that mimic the natural ligand of receptors for signalling molecules interefere with their signalling to promote viral entry into the cell and spread of infection. (Bomsell) Conformational changes resulting from the binding of a primary receptor that allow the binding of a fusion receptor are a common mechanism among various types of virus, including influenza and HIV type 1, examples and brief description. Similar to Influenza . Multiple receptors could be coreceptors and act together either to modulate each other or to contribute complementary functions. Alternatively, the receptors might act sequentially. Binding of the virus to the first receptor could cause changes in the virus or host that are necessary before the second receptor can bind (50). For those viruses in fluids with flow, such as blood or respiratory secretions, the initial binding must be able to effect rapid docking of the virus to its host cell. (Haywood) As previously stated, some viruses recognise more than one cellular receptor. The same receptor may also be used by more than one type of virus. (see table 1) Often, these are highly abundant in many tissues, for example, heparan sulfate can serve as a receptor for many viruses, including Human immunodefiecieny virus, Hepatitis C and Dengue Virus and as a co-receptor for Herpesviruses (excluding EBV). (ODonnel) CAR, acts as a receptor for both coxsackie and adenoviruses. (Schneider) Table 1 illustrates the diversity of cell surface molecules which viruses have adapted to recognise. Some viruses use more than one type of molecule as a primary receptor e.g. reoviruses bind to the beta-adrenergic receptor as well as NAN. (Flint) While the presence of certain receptors on host cells is vital to initiate infection, these interactions are not always sufficient to explain all aspects of cell, tissue and species tropism. (Flint)(Haywood, Schneider) Binding of a viral protein to a cell surface receptor does not necessarily mean a productive infection will follow, since a co-receptor may be absent or functional domains of the receptor may be blocked. (Baranowski) Absence of specific cytoplasmic or nuclear molecules may hinder the replication of some viruses, despite their permissivity. However, even a non-productive infection may induce pathogenic effects, for example, binding to specific receptor may induce the secretion of cytokines. (Schneider) A virus generally cannot infect a cell successfully in the absence of its specific receptor, so the distribution around the body of the receptor will act as a restriction on the range of tissues that can be infected and hence on the number of systems in the body where sig ns and symptoms of infection might be experienced. (Flint) In the true sense of the word, Tropism refers to the specific cells a particular virus is able to replicate in, although the use of receptor by a virus is increasingly a valid definition in the field of virology. Additional factors the cause viral tropism will not be considered in the context of this essay, although they may be mentioned briefly where relevant, since the focus of this review is the link between specific receptor usage and virus tropism and pathogenesis. (Kuhmann) The primary topics explored here are the virus-receptor interactions with cells that allow viruses to enter cells and initiate infection and how this relates to the tropism of the virus at a cellular and organismal level. I am to demonstrate how viral attachment and entry is often a complicated multi-step process, sometimes requiring many different cell and virus molecules. The viruses largely used to illustrate these points, Human Immunodeficiency Virus type 1 (HIV-1), Influenza A and Herpes Simplex Virus type 1 (HSV-1) are human viruses of medical significance, but the tropism of these particular viruses in other animals, along with other viruses specific to other animals will be discussed where relevant. The structure and genomic organisation of these viruses is irrelevant and is only discussed where it relates to the glycoproteins that interact with cellular receptors. Viruses of plants, fungi and bacteria are not discussed The presence on the cell surface of a protein that has been identified as the receptor for a given virus may not be sufficient for a productive viral infection, and there may be multiple mechanisms behind such restrictions: functional domains of the receptor may be blocked in some cellular context, additional proteins (or other cofactors) may be needed, or cells may exhibit impediments for completion of the infection cycle, despite an initial successful interaction with a functional receptor. HSV- Demonstrates how viruses may use a large number of viral proteins and receptors to bind and enter specific cells. (Hayashi and Yoon) and how the interactions are a complex multi-step process. Influenza multiple steps. binds many cell types Tropism is dependent on other receptors and interactions. Of the many examples, the interaction of  the human influenza A virus hemagglutinin  with N-acetylneuraminic acid, and the ensuing  conformational alterations involved  in pH-dependent membrane fusion, are one  of the best characterized at the structural  and functional levels (11) (Baranowski 2001)  example of proteolytic cleavage to aid spread and pathogenesis. Conformational change required for fusion HIV A well-documented case of use of multiple receptos is that of HIV-1 viruses and related viruses. Illustrates how a virus may use multiple coreceptors to mediate entry to different types of cells and thus influence the tropism of this virus. Uses some of the same receptors as other viruses (parallels between HIV, HSV and influenza) Multi-step process The interaction of the virion with the attachment receptor leads to the first conformational changes in the envelope proteins. This step enables the interaction with co-receptors, or entry mediators and further conformational changes at the plasma membrane. In enveloped viruses (top), this may deliver the energy for the direct fusion of the viral envelope and cellular membrane. Some enveloped and non-enveloped viruses require the low pH in acidic endosomes to induce this conformational change. Enveloped viruses may require the low pH to induce membrane fusion (centre). These mechanisms lead to the release and possibly uncoating of the virus genome, and the initiation of the virus replication cycle. Role of Viral Receptor Destruction While non-enveloped viruses typically undergo relase through cytolysis. Influenza and HIV-1 Viruses also demonstrate the importance of receptor-destroying activity on the infectivity of some viruses. This is imperative for the efficient release and cell-cell spread of the virus by preventing the glycoproteins on the newly-emerged virus from binding to the host cell receptors. It is also important for preventing superinfection of cells by the same or different viruses utilising the same receptor, which may result in cell death. The efficient budding and release of Influenza A virus from the host cell relies on the removal of Sialic Acid residues by Neuraminidase. In contract, the HIV-1 virus gp120 envelope glycoprotein downregulates the CD4 receptor after infection of monocytes, by stimulating TNF-ÃŽÂ ± production. Other cellular mechanisms contribute to down-modulation of CD4, including the gene product Nef, which causes CD4 internalisation respectively. The precursor of gp120 and gp41, gp160, has also been found to bind CD4 intracellularly in the presence of viral protein Vpu, resulting in retention of CD4 in the Endoplasmic Rectilium. Enveloped particles leave the infected cell inconspicuously  by budding and secretion. Nonenveloped viruses  are usually thought to undergo release through cell lysis,  but some may escape by secretory mechanisms after  budding into membrane bound compartments and then  losing their membrane (Altenburg et al., 1980). Others  may subvert cellular autophagy pathways to gain access  to exocytic organelles (Jackson et al., 2005).  (Marsh)