Chemical Composition of Cells Test for Starch

Chemical Composition of Cells Test for Starch

A laboratory is a safer and conducive environment to conduct any chemical experiment as it is equipped with requirements such as fire extinguisher and all the chemical reagents needed in an experiment. Carbohydrate is a biological molecule made of carbon, hydrogen and oxygen atoms. Monosaccharides, on the other hand, are fundamental units which store energy in both plants and animals and they also give structure to plant cells (Stick & Spencer, 2010). Monomers that build carbohydrate molecule are monosaccharides which involve glucose, ribose, and fructose. Polysaccharides such as cellulose are formed when three or more monosaccharides are integrated.

A control experiment is a set-up used by an observer to identify any changes to the test subject by comparing it to the dependent variable. Distilled water is used as a control since it is pure and can be considered a standard control. Water is called a negative control since there is no response for an experiment carried out with water.

Materials used to carry out starch test

  • Iodine Solution
  • Benedict’s Solution
  • Peeled potato
  • Heat

Iodine solution is used together with a peeled potato. A drop or two drops of iodine solution is placed on a peeled potato to turn from red to blue-black colour thus indicating the presence of starch (Stumpf & Conn, 2012). Benedict’s solution which is blue is heated to turn to brick-red when carbohydrates are present. According to Stumpf and Conn (2012) copper (ii) ions contained in the Benedict’s solution are converted to copper (i) ions as a result of the presence of reducing property of simple carbohydrates. Thus, the colour changes from blue to brick red.

Table 1.1

Food substance Chemicals used Procedure Results Conclusion
Carbohydrates Iodine Add two drops of iodine solution to a peeled potato. Colour changes from red to blue-black. Starch present.
Carbohydrates Benedict’s solution Heat the Benedict’s solution in the presence of a simple carbohydrate. Colour changes from blue to brick red. Starch present.


Stick, R. and Spencer Williams (2010). Carbohydrates:The Essential Molecules of Life. Elsevier Science.

Stumpf, P.K and Conn E.E. (2012).The biochemistry of plants: Carbohydrates.Editors-in-Chief.\

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