Key Stage 3
Meaning
Sugar is a simple carbohydrate found in food and is a source of energy for respiration.
About Sugar
Sugar Molecules
- Sugar molecules are referred to as 'simple molecules' which can be quickly absorbed into the body to provide energy by respiration.
- You should know:
- Glucose - A sugar found in syrup and sweets.
- Fructose - A sugar found in fruits.
- Sucrose - Found in white sugar which is made of one glucose molecule and one fructose molecule bonded together.
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| There are many different sugar molecules. These are just three examples.
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Sugar in foods
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| Fruit has lots of sugar but is healthy because the sugars are released slowly during digestion and it also has vitamins and fibre inside.
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Yoghurt has a lot of sugar but there are also some health parts like a mineral called Calcium.
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Sweets are full of sugar with nothing healthy in them.
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Energy drinks have nothing healthy in them and are packed with sugar.
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Testing For Sugars
- Glucose and Fructose can be detected with the Benedict's Test.
- Sucrose cannot be detected with the Benedict's Test unless you first react it with dilute Hydrochloric Acid.
Method
- 1. A sample of food is dissolved in water.
- 2. The solution is added to blue Benedict's solution in a boiling tube.
- 3. The solution is kept at 90°C for up to 10 minutes.
- 4. A colour change indicates the presence of glucose or fructose. If they are present the solution will eventually turn brick red or brown.
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| When sugar is present the Benedict's solution turns from blue through several colours until it becomes brick red or brown.
If this was done with sucrose the Benedict's solution would stay blue.
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Key Stage 4
Meaning
Sugar is a term used to refer to several monosaccharides and disaccharides.
About Sugar
- Sugar molecules can join together in condensation polymerisation reactions to form polysaccharides.
- The monosaccharide sugars you should know:
- The disaccharides you may know, but do not have to remember:
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| There are many different sugar molecules. These are just three examples.
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Testing For Sugars
- Glucose and Fructose can be detected with the Benedict's Test.
- Sucrose cannot be detected with the Benedict's Test unless you first react it with dilute Hydrochloric Acid.
Method
- 1. A sample of food is dissolved in water.
- 2. The solution is added to blue Benedict's solution in a boiling tube.
- 3. The solution is kept at 90°C for up to 10 minutes.
- 4. A colour change indicates the presence of glucose or fructose. If they are present the solution will eventually turn brick red or brown.
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| When sugar is present the Benedict's solution turns from blue through several colours until it becomes brick red or brown.
If this was done with sucrose the Benedict's solution would stay blue.
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References
AQA
- Sugar, pages 58, 76-7, 88-9, GCSE Biology; Student Book, Collins, AQA
- Sugars (test for), page 28, GCSE Combined Science; The Revision Guide, CGP, AQA
- Sugars (test for), page 32, GCSE Biology; The Revision Guide, CGP, AQA
- Sugars, pages 172-173, GCSE Chemistry; Third Edition, Oxford University Press, AQA
- Sugars, pages 40, 64, GCSE Biology; Third Edition, Oxford University Press, AQA
Edexcel
- Sugars, page 100, GCSE Chemistry; The Revision Guide, CGP, Edexcel
- Sugars, pages 176, 185, GCSE Chemistry, Pearson, Edexcel
OCR
- Sugars, page 23, Gateway GCSE Biology; The Revision Guide, CGP, OCR
- Sugars, pages 20, 40, Gateway GCSE Combined Science; The Revision Guide, CGP, OCR
- Sugars, pages 204, 205, 245, Gateway GCSE Chemistry, Oxford, OCR
- Sugars, pages 38, 47, Gateway GCSE Biology, Oxford, OCR
- Sugars; testing for, page 24, Gateway GCSE Biology; The Revision Guide, CGP, OCR
