1.2 Carbohydrates - monosaccharides

What are carbohydrates composed of?

Carbon molecules (carbo) combined with water (hydrate)

What is a monomer?

Smaller units from which larger molecules are made

What are some examples of monomers?

Monosaccharides, amino acids and nucleotides

What are polymers?

Molecules made from a large number of monomers joined together

What are some examples of polymers?

Proteins and carbohydrates

What are most polymers made up of?

Carbon, hydrogen, oxygen and nitrogen

What is the basic monomer unit in carbohydrates?

A sugar, otherwise known as a saccharide

What is a monosaccharide?

A single monomer

Sweet tasting, soluble substances that have the general formula (CH2O)n, where n can be any number from 3 to 7

What is a disaccharide?

A pair of monosaccharides combined together

What is a polysaccharide?

Monosaccharides combined in much larger numbers

What are some examples of monosaccharides?

Glucose, galactose and fructose

What is glucose?

It’s a hexose (6-carbon) sugar and has the formula C6H12O6

However, the atoms of carbon, hydrogen and oxygen can be arranged in many different ways

For example, glucose has two isomers - alpha and beta glucose

What are some reducing sugars?

All monosaccharides and some disaccharides (e.g. maltose)

What is reduction?

Chemical reaction involving the gain of electrons or hydrogen

What is a reducing sugar?

A sugar that can donate electrons to (or reduce) another chemical, in this case Benedict’s reagent

What is the test for a reducing sugar?

Benedict’s test

How do you test for reducing sugars and what is the result?

1. Add 2cm³ of the food sample to be tested to a test tube. If the sample is not already in liquid form, first grind it up in water

2. Add an equal volumne of Benedict’s reagent

3. Heat the mixture in a gently boiling water bath for 5 minutes

Benedict’s reagent is an alkaline solution of copper (II) sulfate

If reducing sugar is present, solution turns orange-brown colour