Biological molecules

Chapter 3: Biological Molecules

3.1 Formation and Modification of Biological Molecules

  • Carbon's Versatility

    • Carbon forms a wide variety of chains and ring structures; these structures are the backbones of all biological molecules.

    • Most complex molecules based on carbon = organic molecules.

    • Inorganic molecules include small carbon-containing molecules (e.g., CO2).

3.2 Classes of Organic Molecules

  • Four Major Classes

    • Carbohydrates: Energy and structural functions.

    • Lipids: Fats, oils, and cell membranes.

    • Proteins: Enzymes and structural support.

    • Nucleic Acids: DNA and RNA for genetic information.

  • Hydrocarbons: Molecules consisting solely of carbon and hydrogen atoms.

3.3 Hydrocarbon Structures

  • Types of Hydrocarbons

    • Methane (CH4): Simplest hydrocarbon with carbon bonded to four hydrogens.

    • Complex Hydrocarbons: May have chains (linear or branched) or rings (single, double, or triple bonds).

3.4 Functional Groups in Organic Molecules

  • Functional Groups

    • Small, reactive clusters of atoms that confer specific chemical properties to larger molecules.

    • Important Groups: Hydroxyl, carbonyl, carboxyl, amino, phosphate, and sulfhydryl groups.

3.4.1 Hydroxyl and Carbonyl Groups

  • Hydroxyl Group (—OH): Found in alcohols.

  • Carbonyl Group (=C=O): Polar, reactive, involved in aldehydes and ketones.

3.4.2 Carboxyl and Amino Groups

  • Carboxyl Group (—COOH): Acts as an acid by donating H+.

  • Amino Group (—NH2): Acts as a base, accepting H+.

3.4.3 Phosphate and Sulfhydryl Groups

  • Phosphate Group (—OPO3^2-): Involved in energy transfer and linking molecules (as in DNA).

  • Sulfhydryl Group (—SH): Forms disulfide linkages, important in protein structure.

3.5 Isomers

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

    • Stereoisomers: Mirror images (e.g., D and L forms).

    • Structural Isomers: Differ in atom arrangement (e.g., glucose vs. fructose).

3.6 Adding and Removing Water

  • Reactions

    • Dehydration Synthesis: Formation of large molecules by removing water.

    • Hydrolysis: Breakdown of molecules by adding water.

3.7 Polymers and Macromolecules

  • Polymers: Long chains of monomers linked by covalent bonds (e.g., carbohydrates, lipids, proteins, nucleic acids).

  • Macromolecules: Polymers with molecular weights greater than 1,000 daltons.

3.8 Carbohydrates

  • Functions: Energy provision and storage (starch in plants, glycogen in animals); structural (cellulose).

  • Structure: Composed of carbon, hydrogen, and oxygen (ratio ~1C:2H:1O).

  • Monosaccharides: Simple sugars (C3 to C7); can polymerize to form disaccharides and polysaccharides.

3.9 Polysaccharides

  • Common polysaccharides include plant starches, cellulose, and glycogen.

  • Can be linear or branched.

3.10 Lipids

  • Types of Lipids

    • Neutral Lipids: Energy storage (fats and oils).

    • Phospholipids: Cell membrane formation.

    • Steroids: Hormones.

3.11 Proteins

  • Functions: Provide structure, serve as enzymes, transport, and regulatory molecules.

  • Made of Amino Acids: 20 different amino acids form chains via peptide bonds.

3.12 Nucleotides and Nucleic Acids

  • Nucleic Acids: DNA and RNA, polymers of nucleotides consisting of nitrogenous base + sugar + phosphate group.

  • Base Pairing: Complementary pairing in DNA (A-T, G-C) and RNA (A-U, G-C).

3.13 Study Break Questions

  • Questions focused on the differences between hydrocarbons and organic molecules, functional groups' roles, the difference between dehydration and hydrolysis reactions, and the types of sugars.