Eukaryotic organelles Essay Example for Free

Eukaryotic organelles Essay Eukaryotic organelles Living things have evolved into three categories of closely related organisms, called domains: Archaea, Bacteria, and Eukaryota. Life as we see it each day — including plants and animals — belongs to the third domain, Eukaryota. Eukaryotic cells are a more complex opposed to prokaryotes (simpler based cells), and the DNA is linear and found within a nucleus. Organelles are small structures within cells that perform specialized functions. They are found within the cytoplasm (a semiliquid substance that composes the foundation of a cell) Just as the name indicates, you can think of organelles as small organs. There are a dozen different types of organelles commonly found in eukaryotic cells. Some structures of organelles are membrane bound. The Plasma Membrane is a membrane boundary of a cell, and sorts cell transport and is the outermost cell surface. It separates the cell from the external environment. The plasma membrane is made mostly of proteins and lipids, especially phospholipids. The lipids occur in two layers (a bilayer). Proteins embedded in the bilayer appear to float within the lipid, so the membrane is constantly in flux. The membrane is therefore referred to as a fluid mosaic structure. Within the fluid mosaic structure, proteins carry out most of the membranes functions (prokaryote and eukaryote cell structure, 2000. ). The nucleus of eukaryotic cells is composed primarily of protein and deoxyribonucleic acid, or DNA. The DNA is organized into linear units called chromosomes. Functional segments of the chromosomes are referred to as genes. Approximately 100,000 genes are located in the nucleus of all human cells. Within the nucleus are two or more dense organelles referred to as nucleoli. In nucleoli, submicroscopic particles known as ribosomes are put together before their passage out of the nucleus into the cytoplasm. The endoplasmic reticulum (ER) is an organelle that is a series of membranes extending throughout the cytoplasm of eukaryotic cells. In some places, the ER is studded with submicroscopic bodies called ribosomes. The endoplasmic reticulum (ER) consists of two types the rough endoplasmic reticulum and the smooth endoplasmic reticulum. This type of ER is referred to as rough ER. In other places, there are no ribosomes. This type of ER is called smooth ER. The ER is the site of protein synthesis in a cell. Within the ribosomes, amino acids are actually bound together to form proteins. We can take a look at another organelle called the Golgi body (also called the Golgi apparatus). The Golgi body is a series of flattened sacs, usually curled at the edges. In the Golgi body, the cells proteins and lipids are processed and packaged before being sent to their final destination (prokaryotic and eukaryotic cell structure, 2000. ). Lysosomes and vacuoles are membranous sacs. The lysosome is derived from the Golgi body. It is a drop like sac of enzymes in the cytoplasm. These enzymes are used for digestion within the cell. They break down particles of food taken into the cell and make the products available for use. In other words break down old worn-out cell parts within the cell. Vacuoles Eukaryotic cells have their own internal power plant, called mitochondria. Mitochondria are organelles in eukaryotic cells where cellular respiration takes place. Mitochondria contain a short loop of DNA that is distinct from the DNA contained in the cells nucleus. These tiny organelles in the cell not only produce chemical energy, but also hold the key to understanding the evolution of the eukaryotic cell. The mitochondria play a central role in making chemical energy available to the cell. Cells which require and expend a lot of energy typically have a lot of mitochondria (Muscle cells). Plastids are major organelles found in the cells of plants and algae. They are the site of manufacture and storage of important chemical compounds used by the cell. Plastids often contain pigments used in photosynthesis and the types of pigments present can change or determine the cells color. They possess a double-stranded DNA molecule, which is circular. Microbodies are Membrane-bound organelle sacs that contain enzymes that manage many different metabolic reactions. One type of micro body, the peroxisome, regulates the conversion of fats to carbohydrates. Peroxisomes in the liver and kidney cells could also show important in the detoxifying of certain compounds such as ethanol in alcoholic beverages. Peroxisomes occur in both plant and animal cells. Organelles, which generally do not contain membranes, are ribosomes, cytoskeletal structures, centrioles, cilia, and flagella. Centrioles are small cylindrical-shaped structures that are found just outside of the nucleus. Their purpose is to produce microtubules that help move chromosomes during cell division. The cytoskeleton gives strength and flexibility to the cell. It consists of four major components microfilaments, intermediate filaments, thick filaments, and microtubules. Each of these four components provides different functions related to the overall purpose of the cytoskeleton. Cilia, tiny hair-like structures are numerous and are found on the surface of the cell. Their purpose is to move fluids or solids across the cell membrane. The trachea and bronchi are lined with cilia to move mucous that is secreted by the cells lining the trachea up to the pharynx (throat) where the mucous is either coughed up or swallowed. A flagellum is a long hair-like structure that performs a whip-like movement. The male sperm cell is the only cell in humans that contains a flagellum, which helps the sperm cell swim up the female oviduct. Ribosomes are small granular structures that are either attached to the endoplasmic reticulum or are free, floating in the cytoplasm. Proteins are produced on the surface of ribosomes (Unknown, 2012. ). Every part of the cell has a function. Membranes are essential to the organization of living processes within cells because they separate the cell from the outside world. They also separate compartments inside the cell to protect the important processes and events that occur. Cellular membranes have many functions in the different regions and organelles of a cell. All membranes contain proteins and lipid. However, the amount of each may vary depending on the membrane. Cell membranes are made up of two layers of phospholipids. Phospholipids have hydrophilic (water-loving) heads and hydrophobic (water-repelling) tails. Water exists on both the exterior and interior sides of the membrane. The hydrophobic tails hide behind the hydrophilic heads on both sides of the membrane, forming a non-rigid boundary around the inside of the cell. This non-rigid membrane is held in its shape by microfilaments (thin and solid tubes composed of protein) of cytoskeleton (Membrane structure and function, 2009. ). Proteins determine most of the membrane’s functions. One protein can have several functions. Integral proteins – those that penetrate through the phospholipid bilayer – regulate what comes in and out of a cell. Peripheral proteins are like appendages bound to the surface of the membrane. Peripheral proteins can also act as enzymes and transporters, but they only interact with different parts within the same cell. They help transport small hydrophobic molecules, toxins, and antimicrobial peptides. A cell membrane is a great example of a super molecular structure, where many molecules are ordered into a higher level of organization with emergent properties beyond those of the individual molecules (Membrane structure and function, 2009.). As every part of the eukaryotic cell works together to perform a task and function it seems apparent that without the team work of these components, the world would lack mammals, birds, invertebrates, fish, plants, fungi, and complex single celled organisms. The capabilities of long term functionalities are in conjunction with the growth stemming from this wondrous cell called a eukaryote, a milestone in the evolution of life. of the eukaryotic cell was a milestone in the evolution of life.

AIDS and The Nervous System: A Focus On The AIDS Dementia Complex :: AIDS Disease Diseases Essays

AIDS and The Nervous System: A Focus On The AIDS Dementia Complex Infection by the human immunodeficiency virus (HIV), the biologic agent of the AIDS syndrome, has emerged as one of the most important threats to public health in the United States and its incidence is rapidly increasing. A highly lethal disease with over 70% of AIDS patients dying within 2 years of diagnosis. This disease has already become the leading cause of death in men aged 25-44 and women aged 25-34. The Centers for Disease Control have for the purpose of epidemiological surveillance, defined AIDS as a "reliably diagnosed disease that is at least moderately indicative of an underlying cellular immunodeficiency in a person who has no underlying cause of cellular immunodeficiency nor any other cause of reduced resistance reported to be associated with that disease." [5] The pathophysiology of HIV is indicative of a retrovirus. At the cellular level the most distinct feature of AIDS is the depletion of the helper-inducer lymphocytes or T-helper cells. The specific antigen CD4 present on these lymphocytes appears to be the target of the AIDS retrovirus. HIV does not usually cause disease as soon as it is acquired and therefore in most cases, has a latency period which may be variable. The ultimate problem in this disease is the progressive immunosuppresslon due to the lack of lymphocytes. The nervous system is an early and obvious site of disease in AIDS In addition to the opportunistic infections that the defect in cell mediated immunity allows, there is neurologic damage directly attributable to the AIDS virus. Dysfunction’s of practically all parts of the nervous system have been reported as a direct or indirect result of HIV infection [3]. The human immunodeficiency virus directly attacks cells in the nervous system, although it does not cause morphologic injuries to the neurons. It causes disabling, but not necessarily irreversible changes to the brain and spinal cord. The most common manifestation of this virus is a progressive dementia associated with subacute encephalopathy which is a part of the AIDS Dementia Complex. Spinal cord, cranial nerve, and peripheral nerve damage also occur but at a much lower frequency and are less likely to command the overall course or the disease. As more is learned about HIV infection, the effect on the nervous system be comes more apparent. Estimates on the Prevalence of neurologic consequences of AIDS range from 31-65% in adults and 50-90% in children[5].

Engendering violence Essay

Violence could occur in various ways and in different levels. It may happen in the form of physical, sexual, verbal and psychological abuse, and could be inflicted by any individual, groups, institutions or nations. Whatever form of violence is inflicted, it could threaten the body of the violated person in the most complex way (Jarvis, â€Å"world of the body†). The society today is not new with the issue of violence. Every now and then, the media is consistently reporting events that are inhumane. Although violence could occur among different people, it has been well identified that the prevailing cases of violence are those that are gendered-based. Before one could fully identify gender-based violence, it is an imperative to clarify various definitions that are centered to the area being studied. It should be well understood that the usage of the words gender and sex are needed to be given identification in order to fully understand gender-based violence. In many cases the words gender and sex are used alternately; however there is a distinction between the two words. Sex is often referred to as the differences in the physical aspects of males and females while gender is known to be the roles of the males and females that are socially-prescribed. Such gender roles are acquired through the process of socialization (Ward, 2002 qtd in Benjamin and Murchinson 3). While the physical differences between male and female is persistently identified to be something that is easily distinguished and could be possessed in common, the gender roles are wide range and could be found in different aspects of an individual’s life and may apply in various aspects such as access to various resources, responsibilities that are public and private or even during the period of courtship. Although gender roles could be altered in the long run, it should be well understood that these gender roles reflect the position of men, women and children in the society (Benjamin and Murchinson 3-4). Based from these roles, gender-based violence could be identified as a form of violence that is done to an individual in accordance to the role he or she played within the society. Although such violence could also be directed among men, gender-based violence is prevalent among women and girls. The violence inflicted to females intends to empower hierarchies and strengthen gender inequalities (Benjamin and Murchinson 4). The term gender-based violence is now taking a new context where in it tends to examine and deeply understand the violence against women and discusses the role of gender in inflicting the violence. The power of gender relations always place women in a more disadvantaged position compared to their male counterparts. Gender-based violence place women at a level where they have less access to resources, information, decision making, benefits and have lesser hold on their rights. Aside from these, gender-based violence are also closely related to violence against women and girls because of the involvement of the idea that women are the subordinate gender in the society (UNIFEM 2-3). In various nations, women and girls are victims of myriads of forms of violence. Most of the cases of violence were not done randomly. The victims became the targets of the perpetrators because of the reason that they are females. Among the many forms of violence, sexual violence specifically rape is the most commonly inflicted among women. All sexual assaults are done out of aggression, despite of the gender and age of the victim. The primary motivation of the assailant to carry out rape is not centered towards satisfying a sexual desire or an issue of sexual deprivation from the past rather the perpetrator inflicts rape in order to express their power over somebody (Groth qtd in New York City Alliance against sexual assault, â€Å"Factsheets†). In most cases of female rape the act of violence was predominantly done by males who all come from socio-economic classes, racial or other ethnic groups. All through out the world, rape is often directed towards women because of their gender, regardless of their age, ethnicity or political affiliation (UNIFEM, â€Å"violence†). In the United States alone, it was reported that a woman is raped every two minutes. Just in 1995, the number of women who were raped or sexually assaulted reached over 354,670. The risk factors for initiating rape were accounted for early sexual experience, stereotyping which include the negative attitudes of males toward females, consumption of alcohol and the acceptance of rape myths (â€Å"American rape statistics†). In addition, during war and civil conflicts gender-based violence such as rape and sexual abuse were done in order to attack the morale of the enemy including men and women. For others gender-based violence was also conducted as â€Å"spoils of war. † (Benjamin and Murchinson 5) During the 1994 Rwandan genocide, sexual violence, especially rape was directed or encouraged by the Hutu Militia groups in order to strengthen their goal of destroying the whole Tsutsi clan. At this point in time, the violence was directed towards the Tsutsi women due to their gender and ethnicity. Furthermore, the sexuality of the Tsutsi women was also regarded by the Hutu’s, who were the genocide perpetrators, as a medium that could be used by the Tsutsi community to infiltrate the community of the Hutus. Because of this reason, the propaganda of sexually violating the Tsutsi women became prevalent in order to dehumanize and subjugate the Tsusti community as a whole. Aside from the Tsutsi women other Hutu women were also targeted for rape by their own tribesmen because they were associated with Tsutsi men who are considered as an opposition (Norwojee, â€Å"Shattered lives†). During the conflict in Bosnia-Hercegovina, Muslim women were raped and sexually abused as a part of the so-called â€Å"ethnic cleansing† for the establishment of the Greater Serbia, which is said to be ethically pure. On the basis of investigations, it was estimated that over 20,000 women became the victims of rape and sexual abuse. It was also documented that the rape was directed among the women in order to impose humiliation among the victims, their families and the community where they belong (WomenAid International, â€Å"EC investigative mission†). Much has been written about the prevalence of rape and rape reporting among females. However, it was stated earlier in the study that gender-based violence could also occur among males. In the case of rape, males are often disregarded about the issue because of the social context that males are the initiators of the sexual act, or if not they are considered as the dominating gender and that the women should be take the submissive role (Gagnon and Simon, 1973; Schneider & Gould, 1987 qtd in Duncan and William, â€Å"Gender role,† 1). Despite this traditional sexual script, male rape is also very much similar to female rape. The most common perpetrators of male rape are also males, yet on a larger scale, the involvement of female as accomplices or perpetrators were also reported. In 2002, it was documented that out of eight rape victims, one of those involves a male (RAINN, 2003 qtd in Stanford’s men against violent group, â€Å"male rape†). More often than not, male rape is one of the many violence issues that are least discussed in the society. This is because such issue is often interpreted as an extension of the life in prison and is often regarded as a part of the homosexual subculture (Kaufman et al. , 1980 qtd in Pino and Meier, 1). However, what people do not recognize is the fact that male rape survivors include not only homosexuals but also heterosexuals, teenagers, homosexuals and children. Case research even suggested that males also experience the same reactions felt by females. Alongside with the feelings of depression, anger, self-blame, guilt, sexual dysfunctions, vulnerability and emotional distancing, male rape victims also have to endure unsympathetic attitudes from people even their friends, family and acquaintances (Brochman, 1991 qtd in New York City alliance against sexual assault, â€Å"Factsheets†). Likewise, it was also reported that males are more likely to become victims of multiple aggressors, yet the assailants could inflict sustained physical trauma and male victims could be held as captives for a longer period of time compared to their female counterparts (Kaufman et al. , 1980 qtd in Pino and Meier, 1).

Analysis Of The Article Disparities On Death Row

Being sent to Death Row is the highest prosecution a criminal could be sentenced to and the process when determining of someone deserves a death sentence is a very bias decision. Since 1977 when capital punishment was restored there has been about 20,600 homicides and only about .7 death sentences for every 100 homicides has been given in the Cook county. The decision to impose a death sentence is not only based on the crime done but also the race of the victim. Attorneys at a state level has a less formal guide when giving death sentences. It is commonly seen how race plays a major role in the justice system. As apart of attorney protocol of determining if the death sentence is given it is seen black males will be given a higher sentence versus a white male even if the crimes where similar. In this article â€Å"Disparities on Death Row† published in Grumman points out the unjustness in the justice system. Through ethos, pathos, and logos Cornelia Grumman effectively persuade s her audience to spread the issues of capital punishment assignment. The author of this article is Cornelia Grumman won the Pulitzer Prize in 2003 and found the organization the First Five Years Fund where she advocated for stronger federal policies. The audience she could be targeting would be the government to create stricter guidelines when imposing capital punishment. The purpose of this article is to give awareness of how race can create bias factors in the justice system. It has been commonly seenShow MoreRelatedDeath Penalty Through Life of David Gale Essay952 Words   |  4 PagesThe Life of David Gale makes many arguments against the death penalty throughout the movie showing how far the characters in the movie will go to promote this cause they hold near and dear to their hearts. 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