Part 1 Chemistry of life

Macromolecules - Part 1: Chemical Bonds, Carbon, and Polymers

Summary

• Molecules have distinct properties different from individual atoms.

• Formation of molecules occurs via atom bonding.

• Types of Bonds:

  • Covalent Bonds

  • Hydrogen Bonds

  • Ionic Bonds

• Life is fundamentally carbon-based with water filling spaces between molecules.

• Molecules studied consist of functional groups with varied chemical properties.

• Four types of macromolecules compose all living organisms:

  • Carbohydrates

  • Proteins

  • Nucleic Acids

  • Lipids

Formation of Molecules

• Molecules arise when atoms join through chemical bonds.

• Chemical bonds are interactions holding atoms together:

  • Covalent Bonds

  • Hydrogen Bonds

  • Ionic Bonds

Covalent Bonds

• Formed when two atoms share a pair of valence electrons.

• Types of Covalent Bonds:

  • Single Bond: Sharing one pair of valence electrons.

  • Double Bond: Sharing two pairs of valence electrons.

Electronegativity and Polar Covalent Bonds

• Electronegativity: Ability of an atom to attract electrons; e.g., Oxygen (O) > Nitrogen (N) > Carbon (C) > Hydrogen (H).

• Water is polar due to unequal sharing of electrons, resulting in partial charges.

Hydrogen Bonds

• Formed between partially positive hydrogen atoms and partially negative atoms from different molecules.

• Common partners in living cells are Oxygen or Nitrogen.

Water in Living Organisms

• Cells consist of 60-80% water, essential for life.

• Significance of water includes:

  • High Heat Capacity

  • High Heat of Vaporization

  • Polar Solvent properties

  • High Reactivity

  • Tissue Cushioning properties

Properties of Water

• High Heat Capacity: Moderates climate by requiring significant energy to increase temperature.

• High Heat of Vaporization: Importance in evaporative cooling, absorbing heat from the environment during phase change.

Polar and Nonpolar Molecules

• Hydrophilic Substances: Ionic or polar substances that dissolve in water due to hydrogen bonding.

• Hydrophobic Substances: Nonpolar molecules that aggregate together.

Characteristics of Water

• Reactivity: Involves in hydrolysis and dehydration synthesis reactions.

• Cushioning: Protects organs from trauma, e.g., cerebrospinal fluid.

Ice and Density

• Ice floats because it is less dense than liquid water due to the formation of a crystal lattice structure.

Cohesion and Surface Tension

• Water molecules resist separation, leading to surface tension, facilitating water transport in plants.

Ions and Ionic Bonds

• Ions: Charged atoms/molecules.

  • Cations: Positively charged due to electron loss.

  • Anions: Negatively charged due to electron gain.

• Ionic bonds form due to electrostatic attraction between cations and anions (e.g., NaCl).

Classes of Compounds

• Inorganic Compounds: Lack carbon; includes water, salts, acids, and bases.

• Organic Compounds: Contain carbon; includes carbohydrates, fats, proteins, and nucleic acids.

Importance of Carbon in Biological Molecules

• Living organisms are carbon-based; Carbon can form four stable bonds, emphasizing its versatility.

• Carbon can create many different structures:

  • Linear forms

  • Ring forms

Functional Groups

• Functional groups are specific groups of atoms that confer distinct chemical properties to molecules.

Summary Table: Functional Groups

Part 1

• Amino Group: Forms amines; acts as a base.

• Carbonyl Group: Forms aldehydes and ketones; involved in reactions with larger molecules.

• Carboxyl Group: Forms carboxylic acids; acts as an acid.

Part 2

• Hydroxyl Group: Forms alcohols; makes compounds more soluble in water.

• Phosphate Group: Involved in energy transfer; releases energy when bonds break.

• Sulfhydryl Group: Forms thiols; can form disulfide bonds in proteins.

Macromolecules

• Four types: Proteins, Carbohydrates, Lipids, Nucleic Acids.

• Most are polymers built from smaller monomers, referred to as macromolecules.

Reactions Involving Polymers

• Condensation Reaction: Monomers combine to form polymers, releasing water.

• Hydrolysis Reaction: Polymers break down into monomers, utilizing water.