Structure and Functions of Organelles - Essay Example

Name : xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Tutor : xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Title : SCIENTIFIC ESSAY TITLE "CELL CITY” : Date : xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx @ 2010 Introduction A cell can be described as an independent unit that replicates itself and may be a unit of life which functions on its own for instance in unicellular or single celled organisms A cell also exists as part of a unit in an organism made of many cells or multicellular organisms like animals Kerfeld, Ca; Sawaya, et al (2005).Specialization of cells refers to the structural modification and differentiation in order for them to play certain different and specific functions. This means that a cell acquires special structures that can help it perform its functions effectively. For example a sperm cell is found having a long tail that is necessary for swimming in order to reach the ovum for fertilization to take place; Alberts, Bruce et al. (2002). Organelles are sub-units found within a cell that are specialized to perform certain specific functions. Each of the organelles is normally enclosed separately in two lipid layers. The term organelle is derived from the relationship between the body and the organs. So many types of organelles exist especially in eukaryotic cells. Examples of cell organelles include mitochondria, endoplasmic reticulum, nucleus and lysosomes; Kerfeld, Ca; Sawaya, et al (2005). Cells are normally enclosed in a membrane known as the cell membrane. Each cell is therefore considered a compartment since all of its sides are bound by the cell membrane. The protoplasm of the cell is fully separated from the external environment. This helps the cell to maintain certain molecules within its inside so that reactions can take place in an organized manner; Alberts, Bruce et al. (2003). The membrane of the cell permits selective passage of materials into and out of the cell. In the case of cell belonging to animals the membrane of the cell is important in identifying cells of similar type by use of certain molecules on its surface. These structures are referred to as cell organelles and they create separate compartments in the cell cytoplasm. This is the process of compartmentalization in the cell and it is important since it assists when specific functions need to be undertaken in specific parts of the cytoplasm. Some organelles such as ribosome are not enclosed in membranes. Those organelles bound by membranes such as chloroplasts, endoplasmic reticulum, mitochondria and golgi complex are known as eukaryotic cells; Alberts, Bruce et al. (2002). Organelles within the cell work in coordination in order to achieve a common purpose. The common goal here is the smooth running of the cells and eventually the whole body of the organism. Interrelationships between cells come about because some organelles perform complementary functions to other organelles within the same cell. Other organelles depend on others for certain secretions or activities that should be done. The organelles therefore operate as a team to achieve the goals of the cell. If any of them fails to play its part then other organelles are affected and the cell fails to function properly. For example the role of the nucleus is to control other cell activities. If it fails then the rest of the cell organelles may not function because they have no instructions to operate on. Similarly if the lysosomes fail to destroy worn out parts and digest food then dead and poisonous material will pile inside the cell and overwhelm the cell membrane thus causing death to the entire cell (Alberts 2003). Structure and functions of organelles Organelles have different functions in the cell that when combined make the entire cell a fully functional unit. Cell organelles carry out the life functions within them. They act as work houses inside the cells. Each organelle must perform its role for the smooth running of the activities of the cell and the body to be realized (Campbell, Neil 2006).They are made of different densities and size. The cell membrane as the first organelle is the outermost layer in animal cells enclosing the inner contents of the cell. It is made of a phospholipids layer sandwiched by two layers of protein. In plant cells there is another outer layer called cell wall that covers the cell membrane. The function of the cell membrane is to protect the underlying parts of the cell from the external environment as well as allowing materials in and out of the cell; Alberts, Bruce et al. (2002). These materials include waste products from respiration processes in the cell as well as others that enter to take part in the metabolic processes such as water and carbohydrates. Another organelle is the cytoplasm whose function is to provide the medium in which reactions take place. It has organelles and inclusions like fat droplets, glycogen, starch and other dissolved substances. Mitochondria are also found within the cell and they act as sites where respiratory reactions take place to produce energy. The mitochondria have both inner and outer membranes. The inner membranes serve to increase the surface area for respiration in the cell since they are folded into curves called cristae.The membrane on the outside is smooth and unfolded. Cells that have high needs like muscle sells of energy have a large number of mitochondria.The endoplasmic reticulum is a continuation of the nuclear membrane of the cell; Kerfeld, Ca; Sawaya, et al (2005). They are made from a membrane network that encloses a space. Some endoplasmic reticulum have ribosomes attached to their surfaces and are called rough endoplasmic reticulum. Others have no ribosomes and are thus called smooth endoplasmic reticulum. The rough endoplasmic reticula act as a transport medium for proteins while the smooth endoplasmic reticula transport lipids. Ribosomes can be found scattered within the cytoplasm while others are attached to the surface of the rough endoplasmic reticula. Ribosomes are the organelles in which synthesis of proteins takes place (Murray 1993).They are made of protein and RNA. Another group of organelles is called Lysosomes. They are enclosed by one membrane and have a fluid whose acidic value is very high. They contain lytic enzymes which destroy worn out cell organelles or the whole cell and break down large molecules of food through digestion. Golgi apparatus is sac made from membranes and they are found close to the nucleus; Alberts, Bruce et al. (2002). Golgi apparatus are responsible for the packaging and transportation of glycoproteins. They also take part in the secretion of carbohydrates and proteins after they have been synthesized. Centrioles are important since they participate in formation of cilia and flagella in organisms where they feature and also in cell division. Vacuoles are sacs full of fluid. In certain single celled organisms, food vacuoles are used for storage and digestion of food. Contractile vacuoles in the same organisms do the excretion of unwanted materials in the cell. The nucleus happens to be the biggest organelle enclosed in a membrane. It is enveloped by a nuclear envelope in a selective way. This envelope is made of two membranes joining at regular intervals to make nuclear pores. The nucleus is found at the center of the cell and is responsible for controlling the cell activities; Alberts, Bruce et al. (2003). It carries out storage and transmittance of genetic material. The nucleolus is a spherical structure found within the nucleus and its role is to synthesize ribosomes. It is not bound by any membrane because it is just a space. Chromatin is suspended in the nucleoplasm which is the fluid within the nucleus and its job is to carry the hereditary materials. Endosomes are either vesicular or tubular structures situated between the golgi apparatus and plasma membrane. Their role is to sort and organize traffic in the vesicles through fusing with vesicles or pinching them off (Nelson 2003) Analogy to the city London can be compared to the structure and mode of operation of a cell in many ways. For the city to function properly, various sectors within the city need to be well coordinated and maintained. They need to operate in a special interrelationship where communication becomes important to their operations. The various sectors within the city can be likened to the cell organelles that function together to keep the activities of the cell in motion. For example the mitochondria are responsible for production in the cell. In London they can be compared to power stations that produce energy that runs the city. The endoplasmic reticula are responsible for transport of proteins and lipids just as the golgi apparatus package and transport glycoproteins. In London they can be likened to transport systems that carry products from one place to another; Alberts, Bruce et al. (2003). The nucleus which controls cell operations compares to the city administration that governs and controls other operations. Protein synthesis occurs in ribosomes. They can be termed as the processing and manufacturing industries that produce various items for use. Vacuoles used for storage and digestion of food can be called ware houses and hotels. Lysosomes can be taken to be the garbage collection system that rids London of refuse and unwanted stuff. Centrioles facilitate formation of cilia and flagella for transport. They can be called automobile manufacturing industries that make cars and other transport mechanisms. Conclusion In conclusion cells operate as a team in order for the body to achieve its intended purposes. Each cell is responsible of doing a small bit of work by the help of its organelles. The body is made up of millions of cells (Thomas 2007). Each single cell plays its part in the team and when there total efforts are put together; complex processes within the body are realized. For example production of energy for the body relies on individual efforts done by each cell in oxidation of glucose within the mitochondria. Each cell contributes its portion of energy produced and when the pool is full the body has energy to do massive tasks. Many cells make up tissues that make organs which make organ systems that form the body References Alberts, B(2003).Essential Cell Biology, 2nd ed., Garland Science; Boston, Massachusetts: Pearson Prentice Hall. Nelson P (2003)’International Council of Scientific Unions. Committee on the Teaching of Science Pergamon Press. Kerfeld, Ca; Sawaya, Mr; Tanaka, S; Nguyen, Cv; Phillips, M; Beeby, M; Yeates, To (August 2005). "Protein structures forming the shell of primitive bacterial organelles.". Science (New York, N.Y.) Griffiths G (2007). "Cell evolution and the problem of membrane topology". Nature reviews. Molecular cell biology. Amazon Publishers New York City Campbell, Neil A.; Brad Williamson; Robin J. Heyden (2006). Biology: Exploring Life. Boston, Massachusetts: Pearson Prentice Hall. A Murray, T Hunt; 1993 -The cell cycle: An introduction Oxford University Press, New York, (USA). Thomas, L(2007) The Lives of a Cell: Notes of a Biology Watcher; Viking Publishers ;New York Murray, A(2006).The Cell cycle: An Introduction; Oxford University Press, New York, (USA). Read More