Essential elements for life

  • Major Elements: Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N)

    • Make up ~96% of living matter

    • Involved in key biological molecules like proteins, nucleic acids, carbohydrates, and lipids

  • Minor Elements: Phosphorus (P), Sulfur (S), Calcium (Ca), Potassium (K), etc.

    • Important for structure and function in organisms

Importance of Water

  • Water is a polar molecule: Unequal sharing of electrons results in hydrogen bonding

  • Key Properties:

    • Cohesion: Water molecules stick to each other (surface tension)

    • Adhesion: Water molecules stick to other surfaces (capillary action)

    • High Specific Heat: Stabilizes temperature in organisms and environments

    • Solvent Properties: Dissolves many biological molecules

    • Ice Floats: Solid water is less dense than liquid water, allowing life to exist under ice

Carbon: The Backbone of Life

  • Carbon forms 4 covalent bonds, allowing for complex molecules

  • Diverse Carbon Structures:

    • Chains: Linear sequences of carbon atoms

    • Rings: Cyclic structures found in many biomolecules

    • Branches: Carbon can form branched structures, increasing complexity

  • Functional Groups: Key components that affect molecular properties

    • Hydroxyl (-OH): Found in alcohols

    • Carboxyl (-COOH): Found in amino acids

    • Amino (-NH2): Found in proteins

    • Phosphate (-PO4): Found in nucleotides and ATP

Biological Macromolecules

1. Carbohydrates

  • Monomer: Monosaccharides (e.g., glucose, fructose)

  • Polymer: Polysaccharides (e.g., starch, cellulose, glycogen)

  • Function: Energy storage, structural support (cellulose in plants, chitin in arthropods)

2. Lipids

  • Types: Fats, phospholipids, steroids

  • Function: Energy storage (fats), membrane structure (phospholipids), signaling (steroids)

  • Saturated vs. Unsaturated Fats:

    • Saturated: No double bonds, solid at room temp (e.g., butter)

    • Unsaturated: One or more double bonds, liquid at room temp (e.g., oils)

3. Proteins

  • Monomer: Amino acids (20 different types)

  • Polymer: Polypeptides, which fold into functional proteins

  • Functions: Enzymes, structure, transport, signaling

  • Protein Structure:

    1. Primary: Sequence of amino acids

    2. Secondary: Alpha helices & beta sheets

    3. Tertiary: 3D folding due to side chain interactions

    4. Quaternary: Multiple polypeptides interacting

4. Nucleic Acids

  • Monomer: Nucleotides (sugar, phosphate, nitrogenous base)

  • Polymer: DNA and RNA

  • Function: Store and transmit genetic information

  • DNA vs. RNA:

    • DNA: Double-stranded, deoxyribose sugar, stores genetic info

    • RNA: Single-stranded, ribose sugar, helps in protein synthesis

Summary

  • Life depends on a few key elements, mainly C, H, O, and N

  • Water is vital due to its unique chemical properties

  • Carbon's versatility enables the complexity of life

  • Four major biomolecules (carbohydrates, lipids, proteins, nucleic acids) are essential for structure and function in organisms