Practical Work

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Biological Molecules - Practical Work

Biochemical Tests to Identify Carbohydrates and Proteins (Qualitative Tests)

Carbohydrates

1. Benedict's Test

    - used to detect reducing sugars

    - heated in a water bath

    - blue to green to yellow to orange to brick red (positive)

    - non-reducing sugars change colours the opposite way (negative) 

    - add HCl to non-reducing sugars to get a positive test result

2. Glucose-specific Tests

     - tested with clinistix *****s to detect the presence of glucose

     - ***** changes colour if glucose is present 

3. Iodine Test

     - used to detect starch

     - yellow/brown to blue/black

Proteins

1. Biuret Test 

     - detects the presence of peptide links

     - with potassium/sodium hydroxide solution and dilute copper sulfate solution

     - no protein = stays blue

     - protein = blue to mauve/lilac

2. Amino Acids through Paper Chromatography

   

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