Sugars Flashcards
What elements do all carbohydrates contain?
Carbon.
Hydrogen.
Oxygen.
What monomers make up carbohydrates?
Monosaccharides.
Examples of monosaccharides?
Glucose.
Fructose.
Galactose.
What kind of sugar is glucose?
A hexose sugar - a monosaccharide with six carbon atoms in each molecule.
What are the types of glucose?
Alpha glucose.
Beta glucose.
How are alpha and beta glucose related?
Isomers.
What is an isomer?
Molecules with the same molecular formula as each other, but with the atoms connected in a different way.
How is a disaccharide formed?
Two monosaccharides join together by condensation reactions.
What bond forms between two monosaccharides?
Glycosidic bond.
What disaccharide is formed when glucose and fructose join?
Sucrose.
What disaccharide is formed when glucose and galactose join?
Lactose.
What can sugars be classified as?
Reducing sugars.
Non-reducing sugars.
What is the test for sugars?
The Benedict’s Test.
What colour is Benedict’s reagent?
Blue.
How do you test for a reducing sugar?
Add Benedict’s reagent.
Heat it in a water bath that has been brought to the boil.
If the test is positive a coloured precipitate will form.
How do you know how high the concentration of a reducing sugar is?
The higher the concentration the further the colour change will go.
Green to Yellow to Orange to Brick Red.
What is a more accurate way of comparing concentrations of reducing sugars?
Filter the solution and weigh the precipitate.
OR
Remove the precipitate and use a colorimeter to measure the absorbance of the remaining Benedict’s reagent.
What can still be present if a reducing sugars test is negative?
Non-reducing sugar.
What must be done to test a non-reducing sugar?
Must be broken down into monosaccharides.
How do you break non-reducing sugars down into monosaccharides? And then test them?
Get a new sample of the test solution.
Add dilute hydrochloric acid.
Carefully heat it in a water bath that has been brought to the boil.
Neutralise it by adding sodium hydrogen carbonate.
Carry out the Benedict’s test as you would for a reducing sugar.
