Overview
This lecture introduces the types, structures, functions, and health impacts of carbohydrates, focusing on their essential role in human nutrition and the differences between simple and complex carbohydrates.
Types and Importance of Carbohydrates
- Carbohydrates are a major dietary source worldwide and vital for brain and body energy.
- Ancient diets, like traditional Hawaiian, relied heavily on carbohydrate-rich plants such as sweet potato, breadfruit, and taro.
- Carbohydrates are classified as simple (sugars) or complex (starches and fibers), based on structure and digestibility.
Structure and Classification of Carbohydrates
- Carbohydrates have a 1:2:1 ratio of carbon, hydrogen, and oxygen; general formula CnH2nOn.
- Simple carbohydrates include monosaccharides (glucose, fructose, galactose) and disaccharides (sucrose, lactose, maltose).
- Complex carbohydrates (polysaccharides) include starches, glycogen, and fiber.
Simple Carbohydrates (Sugars)
- Monosaccharides are single-sugar units; glucose is the main energy source for the brain.
- Galactose and fructose have the same chemical formula as glucose but different structures and functions.
- Disaccharides are two monosaccharides joined; sucrose (table sugar), lactose (milk sugar), and maltose (two glucose units).
- Sugar alcohols (e.g., xylitol, sorbitol) are low-calorie sweeteners, less likely to cause tooth decay.
Complex Carbohydrates (Starches and Fibers)
- Starches are polysaccharides found in grains, legumes, and root vegetables; composed of amylose (linear) and amylopectin (branched).
- Glycogen is the storage form of glucose in animals, mainly in liver and muscle.
- Dietary fibers are non-digestible polysaccharides; they are important for digestive health and reducing disease risk.
Types of Dietary Fiber
- Soluble fiber (e.g., pectin, inulin) dissolves in water and is found in oats, beans, and peas.
- Insoluble fiber (e.g., cellulose, lignin) is found in whole grains and vegetables and supports digestive health.
- Functional fibers are added to foods for health benefits (e.g., psyllium); total dietary fiber is the sum of dietary and functional fibers.
Key Terms & Definitions
- Carbohydrate — organic compound with carbon, hydrogen, and oxygen in a 1:2:1 ratio.
- Monosaccharide — single sugar molecule (glucose, fructose, galactose).
- Disaccharide — two monosaccharides linked together (sucrose, lactose, maltose).
- Polysaccharide — long chain of monosaccharides (starch, glycogen, fiber).
- Starch — plant energy storage polysaccharide.
- Glycogen — animal energy storage polysaccharide.
- Dietary fiber — indigestible plant polysaccharide beneficial for health.
- Functional fiber — isolated or synthetic fiber added to foods for health benefits.
Action Items / Next Steps
- Review the carbohydrate classification diagram and figures in the textbook.
- Complete any assigned interactive learning activities using a desktop or laptop for best experience.