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.