Macromolecules

Lactose Intolerance and Biological Molecules

  • Importance of Biological Molecules

    • Lactose intolerance illustrates the significance of biological molecules for cellular functions and human health.

    • Interactions between the lactase gene, the enzyme lactase, and lactose drive biological processes.

Introduction to Organic Compounds

Life's Molecular Diversity

  • Carbon-Based Life

    • Organic compounds have at least one carbon atom.

    • Covalent bonding allows carbon to form complex structures:

      • Carbon has four electrons in its outer shell.

      • It forms four covalent bonds to complete its shell.

      • Bonding patterns affect molecular shape.

Structural Models of Organic Molecules

  • Methane

    • Structural formula, ball-and-stick model, and space-filling model demonstrate its shape.

    • The four single bonds of carbon create a tetrahedral structure.

Carbon Skeletons and Isomers

  • Carbon skeletons vary in length and can be branched or unbranched.

  • Isomers: Molecules with the same molecular formula but different structures and properties.

Functional Groups in Organic Molecules

Roles of Functional Groups

  • Functional Groups

    • Attached to carbon skeletons of organic molecules.

    • Participate in chemical reactions and impart specific properties.

  • Main Functional Groups:

    • Hydroxyl Group: -OH

    • Carbonyl Group: =O

    • Carboxyl Group: -COOH

    • Amino Group: -NH2

    • Phosphate Group: -OPO3^2-

  • All groups are polar, making the compounds hydrophilic (water-loving).

Biological Macromolecules

Classes of Macromolecules

  • Four Main Classes:

    • Carbohydrates

    • Lipids

    • Proteins

    • Nucleic Acids

Carbohydrates

Monosaccharides to Disaccharides

  • Monosaccharides: Simplest carbohydrates, with formulas that are multiples of CH2O. Contains hydroxyl and carbonyl groups.

    • Examples: Glucose and Fructose.

  • Disaccharides: Formed from two monosaccharides via dehydration reactions.

    • Example: Glucose monomers can form maltose.

Polysaccharides

  • Long chains of monosaccharides linked through dehydration reactions:

    • Storage Molecules:

      • Starch (plants)

      • Glycogen (animals)

    • Structural Compounds:

      • Cellulose in plant cell walls.

Lipids

Characteristics

  • Lipids: Diverse compounds mainly composed of carbon and hydrogen, primarily energy-storage molecules.

    • Hydrophobic due to nonpolar covalent bonds.

  • Fats (Triglycerides): Composed of three fatty acids and one glycerol molecule, formed through dehydration reactions.

Types of Fatty Acids

  • Saturated Fatty Acids: Maximum number of hydrogens, no double bonds.

  • Unsaturated Fatty Acids: Fewer hydrogens, contain double bonds.

Phospholipids and Other Lipids

  • Phospholipids: Have two fatty acids and phosphate groups, major components of cell membranes.

  • Waxes and Steroids: Waxes provide waterproofing; steroids like cholesterol function in hormone synthesis.

Proteins

Essential Functions

  • Proteins: Polymers made from amino acids. The structure determines function.

  • Protein Classes:

    • Structural (e.g., collagen)

    • Contractile (e.g., muscle movement)

    • Storage (e.g., ovalbumin in eggs)

    • Defense (e.g., antibodies)

    • Transport (e.g., hemoglobin)

    • Signaling (e.g., hormones)

    • Enzymes (e.g., catalysts for biochemical reactions).

Amino Acids and Peptide Bonds

  • Proteins formed from 20 different amino acids linked by peptide bonds; hydration synthesis joins amino acids.

Protein Structure Levels

  1. Primary Structure: Sequence of amino acids.

  2. Secondary Structure: Coiling/folding stabilized by hydrogen bonding (e.g., alpha helix, pleated sheet).

  3. Tertiary Structure: Overall 3D shape.

  4. Quaternary Structure: Association of multiple polypeptide chains (e.g., collagen).

Nucleic Acids

Structure and Function

  • Types of Nucleic Acids: DNA and RNA

  • Composed of nucleotide monomers with sugar, phosphate group, and nitrogenous base (A, T, C, G in DNA; A, U, C, G in RNA).

DNA Structure

  • DNA forms a double helix; bases pair (A-T, G-C).

  • Specific sequences dictate gene information.

Cell Structure

Prokaryotic vs Eukaryotic Cells

  • Prokaryotic Cells: Simpler, smaller, no membrane-bound nucleus, includes DNA in a nucleoid region.

  • Eukaryotic Cells: Larger, have a true nucleus, and compartmentalized organelles.

Functions of Organelles

  • Nucleus: Houses genetic material.

  • Endoplasmic Reticulum: Rough ER synthesizes proteins; Smooth ER synthesizes lipids.

  • Golgi Apparatus: Processes and refines proteins.

  • Lysosomes: Digestive compartments; recycle materials.

  • Mitochondria: Powerhouse, produce ATP.

  • Chloroplasts: Photosynthesis in plants.

Membrane Structure

Fluid Mosaic Model

  • Phospholipid Bilayer: Hydrophilic heads and hydrophobic tails; selectively permeable to molecules.

Transport Mechanisms

  • Passive Transport: Includes simple diffusion, facilitated diffusion, and osmosis.

  • Active Transport: Requires energy to move molecules against a gradient.

Conclusion

Study Tips

  • Flashcards: For cellular components and their functions.

  • Label Diagrams: Practice with unlabeled cell structures.