Chapter5-TheStructureandFunctionofLargeBiomolecules

5.1 Macromolecules Are Polymers, Built from Monomers

  • Polymers: Large molecules made from repeated subunits (monomers) linked by covalent bonds.

    • Examples include carbohydrates, proteins, and nucleic acids.

  • Monomers: The small units that serve as the building blocks of polymers.

5.2 Carbohydrates Serve as Fuel and Building Material

Types of Carbohydrates

  • Monosaccharides: Simple sugars (e.g., glucose, fructose).

  • Disaccharides: Composed of two monosaccharides (e.g., sucrose, maltose).

  • Polysaccharides: Long chains of monosaccharides (e.g., starch, cellulose, glycogen).

Functions of Carbohydrates

  • Role: Provide energy and serve as structural components.

  • Storage: Polysaccharides store energy (e.g., starch in plants, glycogen in animals).

  • Structure: Cellulose strengthens plant cell walls.

5.3 Lipids Are a Diverse Group of Hydrophobic Molecules

Types of Lipids

  • Fats: Composed of glycerol and fatty acids (triacylglycerols).

    • Saturated Fats: No double bonds (solid at room temperature).

    • Unsaturated Fats: One or more double bonds (liquid at room temperature).

  • Phospholipids: Essential for cell membranes; contain hydrophilic heads and hydrophobic tails.

  • Steroids: Characterized by a carbon skeleton of four fused rings (e.g., cholesterol).

Functions of Lipids

  • Role: Energy storage, cell membranes, signaling.

5.4 Proteins Include a Diversity of Structures, Resulting in a Wide Range of Functions

Protein Structure

  • Polypeptides: Chains of amino acids; proteins are made of one or more polypeptides.

  • Amino Acids: The building blocks of proteins, 20 different types.

  • Levels of Protein Structure:

    • Primary: Amino acid sequence.

    • Secondary: Coiled or folded structures (alpha helices and beta pleated sheets).

    • Tertiary: Overall 3D shape from interactions of side chains (R groups).

    • Quaternary: Structure formed by the aggregation of multiple polypeptides.

Functions of Proteins

  • Enzymes, structural support, transport, signaling, and more.

5.5 Nucleic Acids Store, Transmit, and Help Express Hereditary Information

Structure of Nucleic Acids

  • Composed of nucleotides (nitrogenous base, sugar, phosphate group).

    • DNA: Stores genetic information; double helix structure.

    • RNA: Involved in protein synthesis; usually single-stranded.

Functions of Nucleic Acids

  • Store and transmit genetic information through sequences of nucleotides.