Investigating how sugars are metabolised by yeast

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Investigating how sugars are metabolised by yeast.

Aim

The aim of this experiment is to investigate which of the five different forms of sugars namely; glucose, fructose, sucrose, maltose and lactose undergo the most metabolisms by yeast.

Variables

Independent Variable

Type of sugar

Controlled Variables

Temperature of water

Amount of yeast

Time of reaction

Dependant Variable

Amount of Carbon dioxide produced during the metabolic reaction

Apparatus List

Electronic Stopwatch

Thermometer

10cm³ syringe

Burette

Thin rubber tubing

Hot Water bath

Stirring rod

Clamp Stand

Diagram

Method

  • Prewarm Yeast and sugars in water bath at fixed temperature of 50°C.
  • When reached at required temperature, measure out 6cm³ of yeast, with the help of a syringe, as well as 10cm³ of glucose solution, first.
  • Pour into a boiling tube and fit with the rubber tubing.
  • Take the other end of the tubing and place under the upturned burette, which is filled with water in a bowl.
  • Read and record start volume of water on the burette.
  • Start the timer as soon as the rubber tubing is placed under the burette.
  • Time for maximum 10 minutes.
  • Stop the timer and record the change in volume on burette.
  • Repeat this exercise 3 times for each sugar for reliability.
  • Calculate the difference between start and end volume to find out the amount Carbon Dioxide produced.

Background Information

Respiration is the release of energy from  or other organic substances. Energy is required for growth, repair, movement and other .

There are two main types of respiration, aerobic and anaerobic. Aerobic respiration takes place in the presence of oxygen. This is the normal type of respiration that takes place in all living cells. However, in some cases respiration takes places in the absence of oxygen and this is called anaerobic respiration. For example, in human muscle tisssue, if oxygen is not available, sugars breaks down to lactic acid. In yeast, sugars breaks down to carbon dioxide and ethanol and this called alcoholic fermentation. Yeast requires very little energy and when it performs alcoholic fermentation it provides the little energy required for its body activities.

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During alcoholic fermentation, yeast produces a group of enzymes (zymase complex) which breaks down sugars to carbon dioxide and ethanol.

Sugars are groups of carbohydrates which are classified into monosaccharides and disaccharides. The following are the common characters of monosaccharides and disaccharides.

  • They are all organic compounds because they contain carbon.
  • They all contain carbon, hydrogen and oxygen.
  • Hydrogen and oxygen are arranged in the ratio 2:1. For example the molecular formula of glucose is C6H12O6, which means Glucose is made up of Carbon, Hydrogen and Oxygen and the ratio of hydrogen and oxygen is 2:1. The ...

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The experimental method, data collected and background information are all good. A little more attention to detail and careful use of scientific language would have improved this account.