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Investigation to discover the effect of temperature on anaerobic respiration in yeast cells.

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Introduction

Muhammad Versi GCSE Coursework BIOLOGY Investigation to discover the effect of temperature on anaerobic respiration in yeast cells. Introduction Yeast is a single-celled fungus consisting of millions of tiny living cells. Each cell contains a cell wall and oil granules & glycogen that store carbohydrates and lipids. 19.7(a) A yeast cell ribosome droplet membrane Yeast cells feed on a sugar using an enzyme to break it down into ethanol and carbon dioxide. This process is called fermentation or anaerobic respiration. The equation for anaerobic respiration is: Enzymes in yeast Glucose ???? Ethanol + Carbon Dioxide + Energy C6H12O6 ????? 2C2H5OH + 2CO2 + Energy Yeast is usually grown in a solution containing carbohydrates, the yeast pour out enzymes that break the carbohydrates into glucose that is absorbed by the cell. Enzymes are used in living organisms to increase the rate of a reaction such as digestion. A chemical reaction involving an enzyme always involves one substance being changed into another, the initial substance is called the substrate and final substance is called the product. Enzymes have a very precise shape that usually has a dent, this shape is exactly the right size to fit into the substrate molecule. The dent is called an active site. Each enzyme is The substrate slots Designed so that Thetrate molecule Fits exactly into the It. ...read more.

Middle

Once temperatures reach around 50 degrees the enzyme starts to lose its shape and become damaged, this means it cannot catalyse as well so the reaction slows down. If the temperatures increase it eventually becomes denatured and the reaction will stop completely because the enzymes are inactive. If the reaction is below 25 degrees the enzymes will not have enough energy to move around and catalyse substrate molecules, therefore the reaction will slow down at temperatures lower than 25 degrees. I also predict that if the temperature is over 50 C or under 10 C the respiration rate will be slow and take too long for any measurements to be made. This is because enzymes lose their shape if the temperature is too high and become inactive or denatured if it is too low. However I will investigate temperatures above 50 C and below 10 C to be more reliable and accurate in this prediction. Method For this investigation I will use the following set of apparatus: * Delivery Tube * Thermometer * Boiling Tube (with yeast suspension) * Plastic Beaker * Wooden Peg * Pointed Glass Delivery Tube * Test-Tube * Janus Green & Hydrogen Carbonate Indicator & Liquid Paraffin * Timer * Test tube rack Peg Delivery Tube Pointed glass Delivery tube Plastic beaker to act as water bath Test tube Boiling tube with yeast suspension For the investigation I will fill two thirds of ...read more.

Conclusion

Two is a low number for this type of experiment and if my prediction for temperature of enzyme activity is right then four must be one of the highest number of bubbles I should expect to see. Therefore I must increase the time allowed for counting bubbles otherwise there will be a very limited range and the results will be unreliable and inaccurate. I have decided to increase the time allowed for counting bubbles to a minute but not more because the experiment will take too long especially if I am to carry it out three times for each temperature. To make up for lack of bubbles and rate of respiration I have decided to increase the glucose concentration to 20% hoping that this will affect the rate of respiration and the amount of bubbles. My preliminary experiment also helped me to decide other factors such the time to equilibrate and the temperature range. With the lack of bubbles the results will not be so clear and exact so I have decided to limit the range slightly, the temperature range will be form 10C to 80C with measurements made every 10 degrees. I have kept the temperature range quite wide for reliability and for extra support to the conclusion. The preliminary experiment also helped me to understand how to set up the experiment most efficiently and also clarified a few points on the experiment that I was initially unsure of. ...read more.

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