Monosaccharides

🧪 Monosaccharides

🔹 Definition

• Monosaccharides are the simplest carbohydrates that cannot be hydrolyzed into smaller sugars.

• General formula: $(C{H}_{2}O{)}_n$, where $n=3\text{–}7$.

• They are sweet, water‑soluble, and form the basic units of larger carbohydrates.

🔹 Classification

🍬 1. Glucose (C₆H₁₂O₆)

Open‑Chain Structure

• Aldohexose sugar (contains an aldehyde group at C‑1).

• Formula: H–C=O–(CHOH)₄–CH₂OH.

• Found in fruits, honey, and blood (blood sugar).

Ring Structure

• Forms a six‑membered ring (pyranose) by internal reaction between C‑1 and C‑5.

• Exists in α‑ and β‑forms (anomers).

• Stable and predominant in solution.

Examples & Importance

• Main energy source for cells.

• Stored as glycogen in animals and starch in plants.

• Used medically in glucose drips.

🍯 2. Fructose (C₆H₁₂O₆)

Open‑Chain Structure

• Ketohexose sugar (contains a ketone group at C‑2).

• Formula: CH₂OH–CO–(CHOH)₃–CH₂OH.

• Sweetest natural sugar.

Ring Structure

• Forms a five‑membered ring (furanose) by reaction between C‑2 and C‑5.

• Found in fruits, honey, and sucrose.

Examples & Importance

• Provides quick energy.

• Used in food industry for sweetness.

• Metabolized in liver.

📄 3. Ribose (C₅H₁₀O₅)

Open‑Chain Structure

• Aldopentose sugar (five carbons, aldehyde group at C‑1).

• Formula: H–C=O–(CHOH)₃–CH₂OH.

Ring Structure

• Forms a five‑membered ring (furanose).

• Component of RNA, ATP, and coenzymes.

Examples & Importance

• Essential for genetic material (RNA).

• Forms part of nucleotides and nucleosides.

🥛 4. Galactose (C₆H₁₂O₆)

Open‑Chain Structure

• Aldohexose similar to glucose but differs at C‑4 configuration.

• Found in milk sugar (lactose).

Ring Structure

• Forms a six‑membered ring (pyranose).

• Combines with glucose to form lactose.

Examples & Importance

• Important in brain and nerve tissues.

• Used in synthesis of glycolipids and glycoproteins.

✅ Summary for Exams

• Glucose → Energy source (Aldohexose, Pyranose).

• Fructose → Sweet fruit sugar (Ketohexose, Furanose).

• Ribose → RNA sugar (Aldopentose, Furanose).

• Galactose → Milk sugar component (Aldohexose, Pyranose).