Yeast Investigation

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Yeast Investigation

Introduction

In this investigation I am going to try and find the optimum

temperature at which the new strain of yeast respires using trial and

improvement. I will test from 20°c to 70°c as this is the most

suitable. This means that little heating will be needed to get the

maximum respiration in the yeast and therefore the most efficient

alcohol production. Yeast respires glucose an aerobically producing

carbon dioxide and ethanol as waste products. The carbon dioxide is

given off as bubbles and the number given off in a certain amount of

time can be used to estimate the rate of reaction. I will be using

this method in my experiment.

Method

To do this investigation I will test the yeast in a water bath (beaker

filled with water of a certain temperature) so I can adjust the

temperature and mix the yeast with water using a syringe and some

tubing. I will be using 250ml of water, 25g of sucrose (sugar) and 2g

of dried yeast. I will also use tin foil wrapped round the beaker to

keep the temperature from changing.

Fair Test

I will make this experiment a fair test by using the same water bath

syringe and tubing each time and by measuring the water sucrose and

yeast very carefully.

Prediction

I predict that the optimum temperature will be around 20°c as yeast

respires glucose an aerobically and a higher temperature will speed up

the reaction but if the temperature is too high then the reaction will

be slowed down.

Apparatus

Preliminary work

I did a preliminary test in order to help me plan my experiment out

more carefully and so I can get an idea of what's going to happen. I

tested the yeast in temperatures of 20°c and 70°c (the range that I

will be testing in in my final experiment).

Preliminary Results

Temperature tested

Bubbles counted

20°c

15

70°c

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