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Cell Specialisation. The human body is comprised upward of 60,000,000,000 cells, all individually specialised (Dictionary, 2005). This essay will explore how their ultrastructure differentiates them, focusing on a few cells in particular.

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Introduction

Cell Specialisation After looking at a slice of cork under the microscope, Robert Hooke, in 1665, described the shapes he saw as 'cells' thinking of monks' chambers (Iyer, 2009). The 'cell' is the most basic autonomous component of life. The human body is comprised upward of 60,000,000,000 cells, all individually specialised (Dictionary, 2005). This essay will explore how their ultrastructure differentiates them, focusing on a few cells in particular. Animal cells are eukaryotic: they contain membrane-bound nuclei (Miller & White, 2004). This is one of many organelles; it coordinates cellular activity and processes. The nuclear membrane protects the genetic make-up of the cell: DNA (deoxyribonucleic acid) and is perforated by small nuclear pores which allow certain substances to pass in or out of the nucleus. Information (in the form of molecules exiting the nucleus), then travels to the endoplasmic reticulum (ER); a structure continuous with the outer layer of the nuclear membrane. There are two subcategories of ER: rough and smooth. The difference is notable when observed under an electron microscope, in that rough ER appears 'speckled' due to the ribosomes covering its surface (Carter, 2004). Both are responsible for the synthesis of proteins and lipids, which are eventually excreted in the form of vesicles that travel freely through the cytoplasm; cytoplasm refers to cytosol and other organelles. ...read more.

Middle

their identity becomes clear. There are two classifications of adipocyte: unilocular and multilocular. Multilocular brown fat tissue is found in neonates, later being replaced by unilocular white fat tissue (Albright & Stern, 1998). The unilocular adipocyte has a limited number of organelles since the majority of space inside the cell is occupied by a single lipid globule. Its primary function being energy storage as lipids, however it also regulates satiety by the production and release of the hormone leptin. The multilocular adipocyte is more complex. It contains many smaller lipid vacuoles for lipid storage, but also a high abundance of specialised mitochondria for thermogenesis. These mitochondria contain larger and more numerous cristae increasing their metabolic surface area, and are modified to release energy not in the form of ATP but directly as heat (Standring, 2008). Neonates are less active and so less efficient at maintaining body heat. White Adipocyte: Brown Adipocyte: In contrast, neurones are recognisable by their microscopic projections: the dendrites and axon (developed for the transmission of electrical signals). The high level of specialisation prevents replication in most neurones, one exception being in the hippocampus (Holladay, 2004). Within the soma an abundance of ER and ribosomes can be found pertaining to the high level of protein synthesis involved in neurotransmitter production (Standring, 2008). ...read more.

Conclusion

Chromosomes and Sex. Retrieved October 12, 2011, from biology.about.com: http://biology.about.com/od/basicgenetics/p/chromosgender.htm Bowen, R. (2000, April 1). Reproduction. Retrieved October 12, 2011, from www.vivo.colostate.edu: http://www.vivo.colostate.edu/hbooks/pathphys/reprod/fert/fert.html Britanica, E. (2011). Blood. Retrieved October 3, 2011, from Encyclopedia Britanica Online Library Edition: http://library.eb.co.uk/eb/article-257801 Britannica, E. (2011). Nervous System. Retrieved October 3, 2011, from Encyclopedia Britannica Online Library Edition: http://library.eb.co.uk/eb/art-75833 Britannica, E. (n.d.). Nervous System: Neurons [Video]. Retrieved October 3, 2011, from Encyclopedia Britannica Online Library Edition: http://library.eb.co.uk/eb/art-68425 Carter, J. S. (2004, November 02). Cells and Organelles. Retrieved September 26, 2011, from biology.clc.uc.edu: http://biology.clc.uc.edu/courses/bio104/cells.htm Dictionary, T. A. (2005). Cell. Retrieved September 26, 2011, from The American Heritage Science Dictionary: http://www.thefreedictionary.com/cell Holladay, A. (2004). Wonder Quest - Few brain cells reproduce; 17-year cicadas once escaped ice. Retrieved October 11, 2011, from USA Today: http://www.usatoday.com/tech/columnist/aprilholladay/2004-08-13-wonderquest2_x.htm Iyer, S. (2009, September 24). Buildig Blocks of Life. Retrieved September 26, 2011, from ASU Ask a Biologist: http://askabiologist.asu.edu/explore/building-blocks-life Miller, N., & White, I. (2004, May 23). Cellular Ultrastructure. Retrieved September 26, 2011, from biologymad.com: http://www.biologymad.com/cells/ultrastructure.htm#eukaryotic Slomianka, L. (2009). School of Anatomy and Human Biology - Blue Histology - Blood. Retrieved October 3, 2011, from The University of Western Australia: http://www.labanhb.uwa.edu.au/mb140/corepages/blood/blood.htm#Erythroctes Standring, S. [.-i.-C. (2008). Gray's Anatomy, The Anatomical Basis of Clinical Practice, 40th Edition. London: Churchill Livingstone Elsevier. Waugh, A., & Grant, A. (2010). Ross and Wilson Anatomy and Physiology in Health and Illness, 11th Edition. London: Churchill Livingstone Elsevier. ?? ?? ?? ?? Human Physiology Level 3 Elizabeth Chavez 18/10/2011 1 ...read more.

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