Ch 4

Chapter 2 Overview

  • Focuses on the chemistry of macromolecules that are essential for microbiology.

  • Key macromolecules discussed: carbohydrates, nucleic acids, proteins, and lipids.

  • Importance of the functional groups and chemical bonds in understanding these molecules.

Functional Groups and Chemical Bonds

Key Functional Groups

  • Carbohydrates: Hydroxyl (-OH), Carbonyl (C=O) - found in sugars.

  • Nucleic Acids: Phosphate (PO4) - involved in DNA/RNA structure.

  • Proteins: Amino (-NH2) and Carboxyl (-COOH) - key to amino acid structure.

  • Lipids: Mostly hydrophobic groups like fatty acids.

Types of Chemical Bonds

  • Covalent Bonds: Involve sharing of electrons; essential in forming the backbone of macromolecules.

  • Ionic Bonds: Formed through the transfer of electrons, leading to electrostatic attraction between charged ions.

  • Hydrogen Bonds: Weak attractions between polar molecules; crucial for maintaining the structure of proteins and nucleic acids.

Polarity of Macromolecules

Polar vs. Nonpolar Regions

  • Polar Regions: Often involve functional groups (like -OH) that interact with water, influencing solubility and reactivity.

  • Nonpolar Regions: Typically hydrocarbon chains found in lipids, contributing to cell membrane structure.

Influence on Molecular Interaction

  • Polarity affects how molecules interact in biochemical processes, influencing solubility, binding, enzyme function, and cellular compartmentalization.

Case Study: Mars Perseverance Rover

  • Analyzes the importance of finding water and evidence of carbon compounds on Mars as precursors for life.

  • Targeted location: Jezero Crater, suggesting past water flow.

Atomic Structure and Bonding

Atomic Structure

  • Atoms consist of protons, neutrons, and electrons. Example: Carbon has 6 protons and electrons arranged in two shells.

Chemical Bonds Detailed

  • Covalent Bonds: Sharing of electrons (strongest bond).

  • Ionic Bonds: Transfer of electrons, forming cations and anions (sodium chloride example).

  • Hydrogen Bonds: Weaker bonds that form between molecules, crucial for the secondary structure of proteins and base pairing in DNA.

Water as a Critical Compound

Properties of Water

  • Covalent, Polar: Exhibits unique properties essential for life.

  • Universal Solvent: Ability to dissolve many substances, which allows for biochemical reactions.

  • Adhesion and Cohesion: Important for processes like transpiration in plants.

  • High Heat Capacity: Water can absorb large amounts of heat without significant temperature change, stabilizing environments.

Importance in Aqueous Solutions

  • Acids release H+ and decrease pH, while bases release OH- and increase pH, affecting molecular interactions.

Organic Molecules Overview

Types of Organic Molecules

  • Carbohydrates: Energy sources and structural components; include monosaccharides, disaccharides (glycosidic bonds), and polysaccharides (e.g., starch, cellulose).

  • Lipids: Hydrophobic molecules involved in energy storage (triglycerides) and cellular membranes (phospholipids).

  • Proteins: Made of amino acids, involved in structure, enzymes, signaling, and transport (linked by peptide bonds).

  • Nucleic Acids: DNA and RNA, made of nucleotides; their structure includes a phosphate backbone and nitrogenous bases, stabilized by hydrogen bonds in DNA.

Protein Structure

  • Structured into four levels:

    • Primary: Sequence of amino acids.

    • Secondary: Alpha helices and beta sheets formed by hydrogen bonds.

    • Tertiary: 3D shape caused by interactions between R groups.

    • Quaternary: Assembly of multiple polypeptides into a functional protein.

  • Denaturation: Loss of structure and function due to extreme conditions (e.g., heat, pH).

Nucleic Acids

  • Function in energy transfer (ATP), genetic encoding (DNA/RNA), and key structural roles in cells.