Carbohydrates
Sugars and their chains — the body’s most readily available fuel.
- Simple sugars (monosaccharides) — glucose, fructose, galactose; single sugar units.
- Disaccharides — two units joined, such as sucrose (table sugar) and lactose (milk sugar).
- Polysaccharides — long chains: glycogen, the body’s storage form, kept in liver and muscle; and dietary fiber, plant chains the body cannot digest.
What they do
Section titled “What they do”- Quick energy — glucose is the preferred fuel of most cells and the near-exclusive fuel of the brain.
- Energy storage — glycogen buffers blood sugar between meals.
- Structural and recognition roles — sugars attached to proteins and fats act as identity tags on cell surfaces.
Key idea
Section titled “Key idea”Glucose is the central currency of cellular energy; the rest of carbohydrate biology is about storing it, releasing it, and keeping its blood level steady.