Carbohydrates: Structure and Function

Carbohydrates

• Carbohydrates are essential for energy production and are polyhydroxy aldehydes or ketones, or substances that form these upon hydrolysis
• They are present in both animals and plants, and have important structural and metabolic roles
• In plants, glucose produced through photosynthesis can be stored as starch or used to form cellulose
• Animals can synthesize carbohydrates from amino acids, but their primary source is plants
• The brain and red blood cells primarily rely on carbohydrates for energy

Examples of Ketoses of Physiological Significance

• Fructose: A hexose ketone found in fruits and honey
• Dihydroxyacetone: A triose ketone involved in glycolysis

Hexoses of Physiological Importance

• Glucose: A hexose aldose abundant in blood and used as a primary fuel for cells
• Galactose: A hexose aldose found in milk and used in the synthesis of lactose and glycolipids
• Mannose: A hexose aldose found in certain fruits, involved in glycoprotein synthesis

Disaccharides of Physiological Importance

• Sucrose: A disaccharide composed of glucose and fructose, commonly known as table sugar
• Lactose: A disaccharide composed of glucose and galactose, found in milk
• Maltose: A disaccharide composed of two glucose molecules, generated during starch digestion

Glycogen

• A branched glucose polymer synthesized and stored in the liver and muscles
• Serves as a reservoir of readily available glucose for the body

Glycoproteins

• Also known as mucoproteins, are proteins with branched or unbranched oligosaccharide chains that include fucose
• Present in cell membranes, and many proteins are glycosylated (modified with sugar chains)