1.4.13

Required Practical - Enzymes in Digestion

Test yourself

Testing for Carbohydrates, Lipids and Proteins

Reagents can be used to test for the presence of various food substances. The first step is to grind up the food and add distilled water to dissolve some of the food. You can then test for the food substances:

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Starch

  • To test for starch, add iodine solution.
  • It will turn blue-black if starch is present.
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Sugar

  • To test for sugar, add Benedict’s reagent and heat for about two minutes.
  • It will turn any of green, yellow or red if sugar is present.
  • The colour depends on the concentration.
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Proteins

  • To test for proteins, add Biuret solution.
  • It will turn mauve or purple if proteins are present.
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Lipids

  • To test for lipids, add Sudan III (a fat-soluble dye).
  • If lipids are present, a red-stained oil layer will float on the water surface.
  • The presence of lipids can also be tested by adding ethanol.
  • The solution is added to water and shaken. If the solution turns cloudy, lipids are present.

Jump to other topics

1Biology

1.1Cells, Tissues & Organs

1.2Reproduction & Variation

1.3Ecological Relationships & Classification

1.4Digestion & Nutrition

1.5Plants & Photosynthesis

1.6Biological Systems & Processes

2Chemistry

2.1Particles

2.2Chemical Reactions

2.3Atoms, Elements, Compounds

2.4The Periodic Table

2.5Materials & the Earth

2.6Reactivity

2.7Energetics

2.8Properties of Materials

3Physics

3.1Energy

3.2Forces & Motion

3.3Waves

3.4Electricity & Magnetism

3.5Matter

3.6Space Physics

4Thinking Scientifically

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