Podcast
Questions and Answers
What is the primary use of Benedict's test?
What is the primary use of Benedict's test?
What is the characteristic feature of reducing sugars?
What is the characteristic feature of reducing sugars?
What is the result of treating sugars with dilute alkaline solutions?
What is the result of treating sugars with dilute alkaline solutions?
What is the function of the enol forms of sugars in Benedict's test?
What is the function of the enol forms of sugars in Benedict's test?
Signup and view all the answers
What is the resulting product when Cu2+ is reduced in Benedict's test?
What is the resulting product when Cu2+ is reduced in Benedict's test?
Signup and view all the answers
Which ions are reduced by reducing sugars in Benedict's test?
Which ions are reduced by reducing sugars in Benedict's test?
Signup and view all the answers
What is the result of the oxidation of a reducing sugar?
What is the result of the oxidation of a reducing sugar?
Signup and view all the answers
What is the characteristic of the anomeric carbon involved in a glycosidic bond?
What is the characteristic of the anomeric carbon involved in a glycosidic bond?
Signup and view all the answers
What is the correct representation of the disaccharide maltose?
What is the correct representation of the disaccharide maltose?
Signup and view all the answers
Why is sucrose not a reducing sugar?
Why is sucrose not a reducing sugar?
Signup and view all the answers
What is the minimum amount of sugar required for detection by the Benedict's Test?
What is the minimum amount of sugar required for detection by the Benedict's Test?
Signup and view all the answers
What can interfere with the Benedict's Test?
What can interfere with the Benedict's Test?
Signup and view all the answers
Study Notes
Benedict's Test
- Used to detect reducing sugars in biological fluids
- Originally called Fehling's test
Reducing Sugars
- Comprise all saccharides with free or potentially free aldehyde or ketone groups
- These groups are present in the anomeric carbon of individual sugars
- All monosaccharides have free aldehyde/ketone groups, making them reducing sugars
- Examples of reducing sugars include aldoses, ketoses, and monosaccharides with free reducible groups (CHO or C=O) and adjacent free hydroxyl groups
Isomerization (Lobry de Bruyn-Van Ekstein Reaction)
- Occurs when sugars are treated with dilute alkaline solutions
- Aldoses and ketoses isomerise to form the same endiol in dilute alkali
- Example: D-Glucose, D-mannose, and D-fructose form the same endiol in dilute alkali
Reaction with Benedicts Reagent
- Reducing sugars react with Cu2+ (cupric ion) in Benedicts Reagent to form Cu+ (cuprous ion)
- Cu+ is less soluble and forms a yellow/red solid precipitate (Cuprous oxide, Cu2O)
- The reducing sugar is oxidized to the corresponding carboxylic acid
Disaccharides
- Consist of monosaccharides joined covalently by O-glycosidic bonds
- Example: Maltose, lactose, and sucrose
- Maltose is a reducing disaccharide because the anomeric carbon of one glucose molecule is available for oxidation
Polysaccharides
- Examples: Starch, glycogen, and cellulose
- The end of the chain with a single free anomeric carbon is called the reducing end of the chain
Sucrose
- A disaccharide of glucose and fructose
- Contains no free anomeric carbon atom
- Not a reducing sugar and has no reducing end
- Abbreviated name: Glc a(1→2) Fru or Fru β(2→1) Glc
- Major intermediate product of photosynthesis
- Principle form of sugar transport in plants
Limitations of Benedict's Test
- Has a sensitivity limit of 0.1% to 0.2% sugar
- May be affected by urates and excess ammonia and ammonium salts
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
This quiz is about Benedict's test, originally Fehling's test, used to detect reducing sugars in biological fluids. Reducing sugars have free or potentially free aldehyde or ketone groups, making all monosaccharides reducing sugars.
