Carbohydrate: Homopolysaccharides

📌 Definition & Classification
🖇 Polysaccharides = Carbohydrates with >10 monosaccharide units linked by O-glycosidic bonds.
🟠 Main functions: Storage + Structural support.
🟣 Types:

• Homopolysaccharides → same monosaccharide units.
• Heteropolysaccharides → different monosaccharide units.

📌 Homopolysaccharides (Glucosans & Fructosans)
🟣 Glucosans → made of D-glucose units.
🟣 Fructosans → made of D-fructose units.

🖇 A. Glucosans Types

📌 1. Starch (Plant Storage Form)

• Composed of Amylose (15–20%) + Amylopectin (80–85%).
• Amylose: Linear chain, α-1,4 bonds, water-soluble, forms helix.
• Amylopectin: Branched chain, α-1,4 + α-1,6 linkages (every 24–30 units), water-insoluble.
• Hydrolysis: by α-amylase / HCl → dextrins → maltose.

🚨 Clinical Importance:

• Main dietary carbohydrate source.
• Digestion begins in mouth → salivary amylase.

📌 2. Glycogen (Animal Storage Form)

• Similar to amylopectin but more branched (every 8–12 glucose units).
• Stored mainly in liver & muscles.

🟣 Functions:

• Liver glycogen: maintains blood glucose (10–18 hrs fasting).
• Muscle glycogen: provides energy for muscle contraction.

🚨 Clinical Importance:

• Rapid glucose release due to high branching → vital for energy demand.

📌 3. Dextrins

• Hydrolytic products of starch (by amylase).
• Sequence: Starch → Amylodextrin → Erythrodextrin → Achrodextrin → Maltose.
• Used in: infant feeding.

📌 4. Dextrans

• Synthetic, branched glucose polymers.
• Bonds: α-1,3 and α-1,6 (at branches).
• Produced by oral bacteria → form dental plaque.
• Medical use: plasma substitute (in shock therapy).

📌 5. Cellulose (Structural Polysaccharide)

• Linear chain of β-glucose units (β-1,4 linkages).
• Insoluble in water, non-digestible by humans (no β-1,4 enzyme).
• Main plant structural material.

🚨 Clinical Importance:

• Major component of dietary fiber → essential for digestive health.

🖇 B. Dietary Fiber
🟣 Components: Cellulose, Pentosans, Gums, Pectin, Lignin.
🟠 Types:

1. Soluble fiber (e.g., gums in fruits, oats) → dissolves in water.
2. Insoluble fiber (e.g., cellulose in vegetables, wheat) → doesn’t dissolve.

🚨 Clinical Importance:

• ↓ Colon cancer risk (absorbs toxins, fermented → anti-cancer fatty acids).
• ↓ Blood cholesterol (binds bile acids & cholesterol).
• ↓ Cardiovascular risk (inverse relation with MI & stroke).
• ↓ Blood glucose spikes (delays gastric emptying).
• Prevents constipation (absorbs water → bulky stool).
• Helps weight loss (↑ satiety).
• Relieves IBS symptoms.

📌 B. Fructosans: Inulin

• Found in plants (e.g., artichoke roots).
• Made of fructose units (β-1,2 linkages).
• Not digestible by human enzymes.

🚨 Clinical Importance:

• Used for renal function tests (inulin clearance).