Cambridge AS level Biology Notes: Carbohydrates explained by an A* student

CARBOHYDRATES
MONOSACCHARIDES DISACCHARIDES
• General formula: • General formula:
(CH2O)n C12H22O11
• Sugars • Sugars
• Consists of 1 sugar molecule • Consists of 2 monosaccharide molecules
CLASSIFICATION ACCORDING TO NUMBER OF
CARBON ATOMS:
Glucose + Glucose Maltose + Water
3C – Trioses
Glucose + Fructose Sucrose + Water
5C – Pentoses (ribose, deoxyribose)
Glucose + Galactose Lactose + Water
6C – Hexoses (glucose, fructose, galactose)

➢ Names of all sugars end with – ose

Glucose is the most common monosaccharide

Molecular formular of hexose: C6H12O6

Structural formular of hexose:




Alpha glucose Alpha glucose Maltose




ROLES:
Alpha glucose
A source of energy in respiration

• Carbohydrates have a large number of C-H bonds
which can be broken to release a large amount of
energy
• This energy is used to make ATP and Phosphate
• Most important monosaccharide in energy
metabolism: glucose
Beta fructose Sucrose
Act as building blocks for larger molecules

Glucose polysaccharides (starch, glycogen, cellulose)

Ribose RNA and ATP

Deoxyribose DNA