The rate of respiration in yeast and how it is affected by temperature.

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The rate of respiration in yeast and how it is affected by temperature.

Science Biology: Planning  

For my coursework I am going to investigate how temperature can change the rate of respiration on yeast. I shall do this by conducting an experiment which will involve the timing of the yeast, water and glucose. I shall time how long it takes for the yeast mixture to respire 10 bubbles. I have chosen yeast because it responds quite quickly so it doesn’t take all day. When I chose yeast I was aware of the factors that will affect enzymes and living things. These are:

  • Temperature
  • Oxygen availability
  • Glucose availability
  • PH
  • Radiation (Not in my experiment)
  • Water
  • Concentration

    Preliminary Work

I discovered that the PH in the experiment denatures the enzyme as do other enzymes and temperature. Anaerobic respiration is the production of carbon dioxide without the use of oxygen. So all living things need oxygen to aerobically respire and yeast is a living thing. As yeast aerobically respires it produces ethanol which gives us the smell of the alcohol. I am using glucose because it reacts with yeast.

The preliminary experiment showed that as the concentration of the water and yeast solution to the fixed amount of glucose increases the rate of reaction and therefore produces more carbon dioxide, we measured this in how long 10 bubbles took to come out of the water.

For the final experiment I will investigate the rate of reaction when the temperature is changed. I am doing this because the temperature is straight forward to manipulate in a science lesson. In this reaction, yeast cells use glucose (sugar) and oxygen (from the air) to produce energy. They also produce water and carbon dioxide. I am also going to measure the carbon dioxide in how long it takes to respire 1ml, to do this I will use a boiling tube.

Apparatus

  1. Pipette – Used for picking up the glucose and yeast.
  2. Glucose – In the mixture with yeast
  3. Yeast – In the mixture with glucose
  4. Stopwatch – To time how long it takes for the solution to respire 10 bubbles.
  5. Water bath – Heat the glucose and yeast solution to the relevant temperature to get the right result(s)
  6. Trough – This is filled ¾ of the way up with water so I can see when the bubbles come out.
  7. Measuring tubes – To measure the glucose and yeast into.
  8. Boiling tubes – To put the glucose and yeast solution into and the bung on top with the glass tube going under water and one filled with water and turned upside down in the trough.
  9. Glass delivery tube – Bubbles from the respiring yeast pass through this into the water.

Method

I will set the apparatus up as shown in the diagram and time how long it takes for the mixture to respire 1 ml.

I shall take readings from 25ºC to 60ºC at 10ºC intervals. I will start from 20ºC as I found out from my initial investigation that there was no respiration activity below this temperature. I shall proceed in this sequence as it is the easiest way of collecting results and will help to find out other flaws at a lower temp. Also to aid accuracy, I shall take three readings at each interval and take the mean.

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Variables

In my main experiment, I shall use the time taken for the yeast and glucose solution to respire 1 ml as my dependant variable and the temperature as my independent variable

Here is a list of variables that can have an affect on my experiment and also how I will control them if possible:

  • Temperature
  • Amount of yeast
  • Amount of glucose
  • Volume of water

TEMPERATURE

Temperature of the experiment will have a great affect on the results as explained by kinetic theory. Temperature will affect the rate ...

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