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Homeostasis and Feedback

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The Physics and Chemistry of Homeostasis [image003.gif] Melanie Harris Homeostasis and Feedback A) Homeostasis is the maintenance of a stable internal environment within tolerance limits this is the restricted range of conditions where cellular operations are able to work at a consistent rate and maintain life. Homeostasis also adjusts to the changing circumstances of the external environment, e.g. a cold climate. Homeostasis is a self-adjusting system (auto-regulation), which involves biological feedback. Feedback is the general workings of nervous or hormonal regulation within the body. Homeostasis must maintain cells, tissues and the body in a state of equilibrium in order for life to be sustained. The human body has particular physical features such as the skin and circulatory system, which help its survival the environment. The metabolism is able to adjust to changes in conditions both internally and externally, as they are experienced. Biological Feedback Negative feedback: when the response reduces the original stimulus. . Negative is the most common feedback in biological systems. '. Blood glucose concentrations rise after a sugary meal (the stimulus) '. The hormone insulin is released '. This speeds up the transport of glucose from the blood '. And into selected tissues (the response) Blood glucose concentrations therefore decrease and this, in turn diminishes the original stimulus. Positive feedback: when the response enhances the original stimulus Positive feedback is less common this is because most changes to the internal environment are a potential threat, enhancing the thereat would be a possible danger. ...read more.


the ears, nose, fingers and toes, in milder cases it causes chilblains, in extreme cases it can lead to thrombosis and dry gangrene. C) Calculate the amount of glucose required to make half a litre of a molar solution of glucose. The molecular formula for glucose is C[6]H[12]O[6] Element Atomic Weight Number of atoms Weight Carbon 12.011 6 72.066g Hydrogen 1.008 12 12.096g Oxygen 15.999 6 95.994g Molecular weight (Sum of the atomic weights) 180.156g 180.156 g of glucose equals 1 mole of glucose To make a one molar solution of glucose you would add 180.156 grams of glucose (1m) and add 1000^ml of water making a litre of a molar glucose solution, divide this by two leaving � a litre of molar glucose solution. D) Write the following chemical reaction equations in symbols and balance them (i) Hydrogen peroxide decomposing into water and oxygen. Hydrogen peroxide = H[2]O[2][] Water = H[2]O Oxygen = O[2] 2H[2]O[2 ]� 2H[2]O + O[2] (ii) Magnesium and oxygen into magnesium oxide. Magnesium = Mg Oxygen = O[2] Magnesium oxide = MgO Mg + O[2] � 2MgO (iii) Sodium hydroxide and hydrochloric acid into sodium chloride and water. Sodium hydroxide = NaOH '. Sodium = Na '. Oxygen = O[2] '. Hydrogen = H Hydrochloric acid = HCl '. Hydrogen = H '. Chloride = Cl Sodium chloride = NaCl '. Sodium = Na '. Chloride = Cl Water = H[2]O NaOH + HCl � NaCl + H[2]O E) ...read more.


5 pieces of potato were placed in to the flask. The experiment was then repeated for different vols of Hydrogen peroxide. Measurements Time (in minutes) Amount of oxygen collected in mls 4 vols 8 vols 12 vols 20 vols 0 0 0 0 0 1 0.3 0.1 0.1 0.5 2 0.2 0.15 0.2 1.0 3 No change 0.15 0.3 1.5 4 0.2 0.4 2.0 5 0.25 0.5 2.57 Observations In the flask it was clear that a reaction was taking place by the observation of bubbles of oxygen gas being released creating a fizzing effervescent reaction, rather like a soluble aspirin. From this experiment I can conclude that a higher concentration of H[2]O[2 ]will cause a faster reaction between the[ ]H[2]O[2 ]and the Catalase. The higher the concentration of Hydrogen Peroxide the more oxygen is given off in the decomposition. Factors that may have affected the experiment: 1) I was restricted by time, it would have been better to have left the experiment to work for longer. 2) The rate of reaction could be affected by movement, i.e. if the flask containing the potato and Hydrogen Peroxide was moved it would have increased the rate of decomposition. 3) A certain amount of user error can be attributed to the experiment as I was working alone it was quite difficult to keep the equipment still, therefore keeping an accurate amount of water in the tube that was measuring the oxygen was quite tricky. References Books: Brooker.C., Human Structure and Function (se), Mosby, 1998, London Marieb.E., Human anatomy and physiology (se), Benjamin Cummings,1992, USA Bailliere's Nurses Dictionary 23^rd edition Harcourt 2000 Journals: Websites: http://newton.dep.anl.gov/askasci/bio99/bio99317.htm [1]www.thestrangesite.com/ medconditions.html [2]http://antoine.fsu.umd.edu/chem/senese/101/moles/glossary.shtml http://www.bham.lib.al.us/tech/sciencefair. ...read more.

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