New
New
Year 10
OCR
Foundation

Tests for biological molecules

I can carry out tests for biological molecules, including sugars, starch, proteins and lipids.

New
New
Year 10
OCR
Foundation

Tests for biological molecules

I can carry out tests for biological molecules, including sugars, starch, proteins and lipids.

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Lesson details

Key learning points

  1. A reagent called Benedict’s solution is used to test for reducing sugars, including glucose.
  2. A reagent called iodine solution is used to test for starch, a type of carbohydrate.
  3. A reagent called Biuret solution is used to test for protein.
  4. Ethanol (a type of alcohol) is used to test for lipids.
  5. Interpretation of qualitative food test results.

Common misconception

Mistakes on method, results confusion, and poor descriptions using inaccurate terminology.

Methods and results are described, demonstrated and tested throughout, and methods tried by students with results gathered and analysed. Repeated review of results occurs throughout the lesson, and methods and results are applied to novel questions.

Keywords

  • Reagent - A chemical used to test for a type of biological molecule.

  • Qualitative - A test in which the result is based on an observation.

  • Quantitative - A test in which a measurement produces numerical data.

Allow the students to complete these practicals by themselves. Allow them to use coloured pencils to illustrate their note taking, and consider memory hooks like 'purple protein' to remember the test and its results.
Teacher tip

Equipment

Distilled water, Benedict's solution, Biuret's solution, Sodium Hydroxide, Iodine solution, Ethanol, test/boiling tubes, bung, pipettes, 60 degree water bath, safety goggles.

Content guidance

  • Equipment requiring safe usage.

Supervision

Adult supervision recommended.

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Video

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6 Questions

Q1.
True or false? Proteins and carbohydrates are polymers.
Correct answer: true
false
Q2.
Join the polymer to its monomer.
Correct Answer:protein,amino acids

amino acids

Correct Answer:carbohydrates,sugar

sugar

Q3.
True or false? Enzymes are proteins.
Correct answer: true
false
Q4.
Which of these is a use for lipids in an organism?
making cell walls
making cellulose
Correct answer: making cell membranes
making enzymes
making energy
Q5.
True or false? Animals store carbohydrate as glycogen.
Correct answer: true
false
Q6.
What elements do carbohydrates contain?
An image in a quiz
water
Correct answer: carbon
Correct answer: oxygen
nitrogen
Correct answer: hydrogen

6 Questions

Q1.
Match the reagent to the nutrient it us used to test for?
Correct Answer:iodine,starch

starch

Correct Answer:Benedict's solution,reducing sugar

reducing sugar

Correct Answer:Biuret solution,protein

protein

Q2.
What colour does iodine turn in the presence of starch?
Correct answer: black
orange
yellow
green
violet
Q3.
What substance can be used to test for the presence of lipids?
Correct Answer: ethanol, alcohol
Q4.
Is this a positive or a negative test for Benedict's solution?
An image in a quiz
Correct answer: positive
negative
Q5.
What colour does Biuret solution turn if it comes into contact with protein?
Correct Answer: Purple, Violet, Light purple
Q6.
True or false? This food contains a small amount of reducing sugar?
An image in a quiz
true
Correct answer: false
Q4 UYSEG Q6 UYSEG

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