MOLECULES OF LIFE

Carbohydrates (elements (CH₂O)_n

Organization:

Monosaccharides

Glycoside linkage to form disaccharides

The two sugars are joined by condensation and may be broken by hydrolysis.

Different monosaccharides can be used:

Polysaccharides : Common ones based upon glucose

FUNCTIONS OF THE CARBOHYDRATES

Sugars (mono and disaccharides) - small molecules, soluble in water:

• maintenance of osmotic balance (e.g. salts in blood plasma, plant cell turgidity)
• transport of energy reserves (e.g. glucose in blood or sucrose in sap)
• energy substrate (respiration and photosynthesis)
• energy store (sugar cane)
• flavouring (fruits).
• reward (nectar)
• precursors (building blocks) of polysaccharides, nucleotides and amino acids.

Polysaccharides - large molecules, insoluble in water.

• osmotically inactive carbohydrate storage (seeds, roots, chloroplasts)
• structural (cellulose in plants)

• Introduction
• Lipids
• Amino acids and proteins
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© Paul Billiet 2009