2.3 Carbohydrates to Lipids

• Carbohydrates contain carbon, hydrogen and oxygen.
• Glycosidic linkages connect carbohydrates to other groups which could be carbohydrates.
• Monosaccharides can be connected via condensation reactions.
• A group of two monosaccharides joined together by glycosidic linkages is called a disaccharide.
• A group of three or more (usually hundreds to thousands) monosaccharides joined together by glycosidic linkages is called a polysaccharide.
• The 3 main monosaccharides are glucose, galactose and fructose.
• The 3 main disaccharides are lactose, sucrose and maltose.
• The 3 main polysaccharides are cellulose, glycogen and starch.
• Maltose is composed of 2 glucoses.
• Sucrose is composed of 1 glucose and 1 fructose.
• Lactose is composed of 1 glucose and 1 galactose.
• Maltase is an enzyme that breaks down maltose.
• Sucrase is an enzyme that breaks down sucrose.
• Lactase is an enzyme that breaks down lactose.
• In an alpha glucose the OH is at the bottom.
• In beta glucose the OH is at the top.
• Starch can either be in the form of amylose or amylopectin.
• Starch is an energy storage polysaccharide found in plants.
• Starch is composed of alpha glucose subunits in 1-4 arrangement.
• Amylose is a linear helical molecule.
• Amylopectin is branched.
• Amylose is harder to digest and less soluble than amylopectin but takes up less space.
• cellulose is a structural polysaccharide found in the cell wall of plants.
• Cellulose is a linear molecule composed of beta glucose subunits in a 1-4 arrangement.
• Ribose is a pentose sugar.
• Glucose is a hexose sugar.
• Beta glucose is indigestible for most animals as they lack the enzyme to break down the bond.
• Glycogen is an energy storage polysaccharide formed in the liver of animals.
• Glycogen is composed of alpha glucose subunits linked together by both 1-4 linkages and 1-6 linkages.
• Glycogen branches.
• The function of lipids can be summarised as SHIPS: storage of energy, hormonal roles, insulation, protection and structural components
• Triglycerides provide long-term energy storage in animals (fats) and plants (oils).
• Phospholipids are the structural component of cell membranes.
• Steroids are hormones in plants and animals and act as a structural element in animal cell membranes (cholesterol).
• Waxes act as a protective layer against water loss in plant leaves and animal skin.