macromolecules


Macromolecules Study Notes (BIOL-1013)






1. Synthesis of Macromolecules



  • Macromolecules (carbohydrates, lipids, proteins, nucleic acids) are built from smaller subunits (monomers).

  • Synthesized through dehydration (condensation) reactions: monomers join by covalent bonds, releasing water.

  • Requires enzymes and energy.






2. Dehydration vs Hydrolysis



  • Dehydration synthesis: links monomers by removing H₂O.

  • Hydrolysis: breaks polymers into monomers by adding H₂O.

  • Opposite processes; both enzyme-driven.






3. Roles of Carbohydrates



  • Energy source: glucose, starch, glycogen.

  • Storage: plants (starch), animals (glycogen).

  • Structure: cellulose (plant cell walls), chitin (fungi, arthropods).

  • Cell communication: glycoproteins & glycolipids on cell surfaces.






4. Carbohydrate Classifications



  • Monosaccharides (simple sugars: glucose, fructose).

  • Disaccharides (two sugars: sucrose, lactose).

  • Polysaccharides (many sugars: starch, glycogen, cellulose, chitin).

  • Comparison:

    • Mono = immediate energy

    • Di = transport form of sugar

    • Poly = long-term storage or structural support







5. Common Examples



  • Monosaccharides: glucose, fructose, galactose.

  • Disaccharides: sucrose, maltose, lactose.

  • Polysaccharides: starch, glycogen, cellulose, chitin.






6. Four Major Types of Lipids



  1. Fats (triglycerides) – energy storage, insulation.

  2. Phospholipids – cell membranes (hydrophilic head + hydrophobic tails).

  3. Steroids – hormones, cholesterol.

  4. Waxes – waterproofing in plants/animals.






7. Role of Fats in Energy Storage



  • High energy per gram (2x carbohydrates).

  • Long-term energy reserve.

  • Provides insulation and cushioning.






8. Saturated vs Unsaturated Fatty Acids



  • Saturated: single bonds only; solid at room temp; animal fats.

  • Unsaturated: double bonds (cis = natural, trans = artificial); liquid at room temp; plant oils.






9. Phospholipids



  • Structure: glycerol + 2 fatty acids + phosphate group.

  • Function: main component of cell membranes (bilayer).

  • Amphipathic: hydrophilic head + hydrophobic tails.






10. Steroids



  • Structure: 4 fused carbon rings.

  • Functions: hormones (estrogen, testosterone, cortisol), cholesterol (membrane stability).






11. Cholesterol in Plasma Membrane Fluidity



  • At high temps: stabilizes, prevents too much fluidity.

  • At low temps: prevents membranes from solidifying.

  • Acts as a “fluidity buffer.”






12. Functions of Proteins



  • Enzymes (catalysts).

  • Structural (keratin, collagen).

  • Transport (hemoglobin, membrane channels).

  • Defense (antibodies).

  • Hormonal (insulin).

  • Movement (actin, myosin).

  • Storage (casein, ovalbumin).






13. Amino Acids & Proteins



  • Proteins are polymers of amino acids (linked by peptide bonds).

  • 20 amino acids with different R-groups → determine protein shape & function.

  • Sequence of amino acids = primary structure.






14. Levels of Protein Organization



  1. Primary – amino acid sequence.

  2. Secondary – α-helices and β-sheets (H-bonds).

  3. Tertiary – 3D folding (R-group interactions).

  4. Quaternary – multiple polypeptide chains (hemoglobin).






15. Protein Shape & Function



  • Function depends on shape (enzyme active site, binding sites).

  • Shape is determined by interactions among amino acids.

  • Denaturation (heat, pH, chemicals) disrupts shape → loss of function.






16. Nucleic Acids



  • Structure: polymer of nucleotides (sugar + phosphate + nitrogen base).

  • Two types:

    • DNA: stores genetic info.

    • RNA: helps in protein synthesis.


  • Compare/Contrast:

    • DNA = double-stranded, deoxyribose sugar, bases A/T/C/G.

    • RNA = single-stranded, ribose sugar, bases A/U/C/G.







17. DNA Structure & Role



  • Double helix, complementary base pairing (A-T, C-G).

  • Stores genetic information for protein synthesis.

  • Passed from generation to generation.






18. RNA Structure & Role



  • Single-stranded, contains ribose and uracil.

  • Types:

    • mRNA: carries code from DNA → ribosome.

    • tRNA: brings amino acids during translation.

    • rRNA: makes up ribosomes.







19. Central Dogma of Molecular Biology



  • DNA → RNA → Protein




  1. Replication: DNA copies itself.

  2. Transcription: DNA → RNA.

  3. Translation: RNA → protein (amino acid chain).



Diagram to memorize:

DNA (nucleus) → Transcription → RNA → Translation (ribosome) → Protein.