Monosaccharides and Disaccharides
In this A-Level Biology Lesson “Monosaccharides and Disaccharides” you will learn that monosaccharides join together to make disaccharides (which in turn make polysaccharides) which they do by means of condensation reactions.
What are Monosaccharides?
Monosaccharides are the basic molecular units (called monomers) of which other larger carbohydrates are composed; a couple of common monosaccharides include the reducing sugars, glucose and fructose.
When a condensation reaction takes place between 2 monomers of α-glucose the formation of the disaccharide, maltose occurs.
When a condensation reaction takes place between a glucose monomer and a fructose monomer the formation of the disaccharide, sucrose (a non-reducing sugar) occurs.
Can you write the definition of a monomer?
“The single unit from which a polymer is made. Monomers join together to form long complex polymers, such as polysaccharides, polypeptides and nucleic acids”.
Can you write the definition of a polymer?
“A long complex molecule composed of many repeating monomers”
What are the four biological molecules you have to know throughout your A-Level Biology?
...Can you state them and their monomers?
What elements make up Carbohydrates?
Carbohydrates contain the elements Carbon, Hydrogen and Oxygen.
The Carbohydrate 'group' includes: -
1. Monosaccharides (monomers)
2. Disaccharides (Dimers) and
3. Polysaccharides (polymers).
Monosaccharides join together to form disaccharides and in turn polysaccharides via condensation reactions.
When only 2 monosaccharides join via a condensation reaction one molecule of water (H2O) is removed and a glycosidic bond between the monosaccharides is formed.
The Disaccharides you have to know, and the monosaccharides that make them up are:
1. Maltose.
Which is composed of 2 α-glucose molecules.
2. Lactose.
Which is composed of Glucose and Galactose.
3. Sucrose.
Which is composed of Glucose and Fructose