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Yeast Respiration

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Biology-Respiration-Rate of Yeast Respiration


An investigation to find out how temperature affects the rate of yeast respiration.


Fixed variables:

Through out the investigation I will keep the amount of yeast/glucose solution the same (50 ml). Also the amount of time I will run the experiment for at each reading will remain constant at 1 minute. The one other thing I will keep the same is the concentration of the Glucose as we are not investigating the affect of glucose concentration on the rate of yeast respiration.

Independent variables:

1. temperature

2. concentration of glucose

3. amount of yeast

4. type of yeast

5. oxygen level

Dependent variable:

I will record the level of the water in the burette Everytime I change the temperature of the water one minute after doing so.


As the temperature increases the rate of yeast respiration will increase then it will descend.



Cell reaction. Glucose+oxygen=carbon dioxide+water+energy.


Single celled microbe from the plant kingdom but has no chlorophyll.


Speed at which something happens.


Amount of energy measured in degrees Celsius.

Scientific knowledge:

I made a prediction on the basis on the theory that when the temperature is increased the particles will collide harder and more frequently at certain temperatures most microbes, such as bacteria and yeast, have a temperature range in which they grow best. If it's either too low or too high then they grow slower and if it's to low they stop growing at all. Yeast grows best around 30-35 degrees Celsius. At this temperature the particles are colliding harder because its kinetic energy is at its best but if you get much above 40 it won't grow at all and the particles kinetic energy has decreased dramatically. Below 30 its growth slows down dramatically and when you get below about 10 it really doesn't grow much at all. This happens because of the enzymes in the yeast. The enzymes that catalyze the biochemical reactions in the yeast cell function at those temperatures. Enzymes also have an optimal temperature range. When you get below that range there ability to catalyze the reaction slows down. Above that temperature and the enzyme begins to become inactive. Because respiration is a biochemical reaction it needs those enzymes to catalyze the reaction. If those enzymes are inactive, deformed or destroyed respiration will be very slow or if it is exposed to a very high temperature the respiration process won't go on.


Name of equipment


Unit of Measurement




Measuring cylinder




electric water bath

delivery tube


calculator Hold large amount of water.

To hold the conical flask (which would be attached to the delivery tube) in place.

To measure temperature

To measure liquids

To cool down water

To heat up water

To measure the volume of liquids

To warm up water used for the water bath and keeps it at a constant temperature

Delivers gases from one container to another

A tube fitted with a stopcock, from which accurate volumes may be delivered.

To find the averages of the result.

Degrees Celsius

Millilitres (ml)

Centimetre squared

Millilitres (ml)


Basin measuring cylinder thermometer burette

Calculator ice electric water bath clamp

Kettle delivery tube beaker conical flask


Simulated experiment:

1. First of all log on to a computer which has the programme which simulates the yeast respiration investigation.

2. The icon on the desktop is called science investigations. Click on it twice to open it up. You will see


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