Chapter 3
Carbohydrates, Lipids, & Proteins
Carbohydrates
Mono/Disaccharides, Reactions, &
Polysaccharides
Sugars (2 types)
1. Monosaccharides
2. Disaccharides
• Three common disaccharides:
Two important reactions in making
and breaking down molecules
1. Dehydration reaction (IB calls
condensation reactions)
2. Hydrolysis
http://www.tvdsb.on.ca/westmin/scien
ce/sbioac/biochem/condense.htm
Polysaccharides (3 types)
3 Types of Polysaccharides
1. Starches
• polymers of glucose
• the storage polysaccharide for plants
• rice, wheat, potato, and corn are major
sources of starch in the human diet.
• starches are insoluble in water and thus
can serve as storage depots of glucose
2. Glycogen
• a short-term storage polysaccharide for animals
• highly branched glucose units put together that
are broken down to meet energy demands of the
body
3. Cellulose
• most abundant polysaccharide on earth
• the major structural material of which plants are
made (wood and plant fibers)
• insoluble and has great tensile strength because
the hydroxyls (-OH) are reversed on the carbon
compared to other polysaccharides
• the polymers can be drawn together into dense,
cable-like strands called microfibrils that can then
be organized into fibrils
• most organisms can’t break cellulose down into
simple sugars because they don’t have the enzyme
cellulase which is necessary to hydrolyze the
glycosidic linkages.
• as a result, plant cell walls are among the strongest
of biological structures.