Biomolecules: Polysaccharides, Nucleic Acids & Protein Structure

🍬 Polysaccharides (Long Sugar Chains)

  • Found in the acid-insoluble pellet of living tissues
  • Like “cotton threads” made of repeating sugar units 🔗
  • Cellulose:
    • Made of only glucose (homopolymer) 🌱
    • Forms plant cell walls (cotton/paper = cellulose!)
    • ❌ No helix structure → Can’t hold I2 (iodine)
  • Starch:
    • Plant energy storage ⚡
    • Forms helices → Holds I2 → Turns blue!
  • Glycogen:
    • Animal energy storage 🐾
    • Has branches → Ends called reducing (right) & non-reducing (left)
  • Inulin: Polymer of fructose 🍎
  • Chitin:
    • Complex polysaccharide in arthropod exoskeletons 🦐
    • Made of amino-sugars (e.g., glucosamine)

🧬 Nucleic Acids (DNA/RNA)

  • Also in the acid-insoluble fraction of tissues
  • Building block = Nucleotide (3 parts):
    • 1️⃣ Nitrogenous base (adenine, guanine, etc.)
    • 2️⃣ Monosaccharide (ribose/deoxyribose)
    • 3️⃣ Phosphoric acid group
  • Nitrogenous Bases:
    • Purines: Adenine (A), Guanine (G) 🟣
    • Pyrimidines: Uracil (U), Cytosine (C), Thymine (T) 🔵
  • DNA vs RNA:
    • DNA: Contains deoxyribose → Deoxyribonucleic Acid 🧬
    • RNA: Contains ribose → Ribonucleic Acid 📝

🧵 Protein Structure

  • Strings of amino acids (heteropolymers)
  • Primary structure = The exact sequence of amino acids in a chain:
    • Like beads on a necklace 🧵
    • First amino acid = “left end”, Last amino acid = “right end”

⭐ NEET Super-Important Concepts ⭐

  1. Polysaccharide Types & Functions: Glycogen (animals), Starch/ Cellulose (plants), Chitin (arthropods)
  2. Iodine Test: Starch turns blue with I2; Cellulose does not
  3. Nucleotide Components: Sugar + Base + Phosphate group
  4. DNA vs RNA Sugar: Deoxyribose (DNA) vs Ribose (RNA)
  5. Protein Primary Structure: Linear amino acid sequence

Keep revising – you’re building a strong biomolecule foundation! 💪