Unit 1: Chemistry of Life

Structure of Water & Hydrogen Bonding

The structure and properties of water are foundational to understanding biological systems. Water's polarity and ability to form hydrogen bonds give rise to many of its unique characteristics, which are essential for life.

• Atom: The smallest unit of matter that retains the properties of an element. Atoms consist of protons (positively charged), neutrons (neutral), and electrons (negatively charged).

• Valence Electrons: Electrons in the outermost shell of an atom, involved in chemical bonding.

• Chemical Bonds: Interactions between atoms that result in the formation of molecules. Types include:

  • Covalent Bonds: Atoms share pairs of electrons. Can be single, double, or triple bonds. Example: (water).

  • Nonpolar Covalent Bonds: Electrons are shared equally, resulting in no charge separation.

  • Polar Covalent Bonds: Electrons are shared unequally, creating partial charges. Example: is polar.

  • Ionic Bonds: Electrons are transferred from one atom to another, creating ions (charged atoms). Example: (sodium chloride).

• Hydrogen Bonds: Weak interactions between a hydrogen atom covalently bonded to a more electronegative atom (like oxygen or nitrogen) and another electronegative atom. Example: hydrogen bonds between water molecules.

• Van der Waals Interactions: Weak attractions due to transient charge differences, important in biological systems (e.g., geckos climbing walls).

Water & Polarity: Water is a polar molecule, meaning it has partial positive and negative charges due to unequal sharing of electrons. This allows water molecules to form hydrogen bonds with each other, leading to properties such as cohesion (water molecules sticking together) and adhesion (water molecules sticking to other surfaces).

• Cohesion: Attraction between water molecules due to hydrogen bonding. Responsible for phenomena like surface tension.

• Adhesion: Attraction between water molecules and other substances.

• Surface Tension: The result of cohesion at the surface of water, allowing small objects to float.

• Example: Water transport in plants relies on cohesion and adhesion to move water upward through xylem vessels.

Reactants and Products: Chemical reactions involve reactants (starting materials) and products (resulting substances). The making and breaking of chemical bonds are central to metabolism and energy flow in biological systems.

Elements of Life

Life is composed primarily of a few key elements, which form the basis of biological molecules.

• Major Elements: Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), Phosphorus (P), and Sulfur (S).

• Trace Elements: Elements required in smaller amounts, such as iron (Fe), magnesium (Mg), and calcium (Ca).

• Role of Carbon: Carbon's ability to form four covalent bonds makes it uniquely suited to form complex, diverse organic molecules.

• Example: Carbon forms the backbone of macromolecules like carbohydrates, proteins, lipids, and nucleic acids.

Biological Macromolecules

Macromolecules are large, complex molecules essential for life. They are typically formed by joining smaller units called monomers into polymers.

• Monomer: A small molecule that can join with others to form a polymer.

• Polymer: A large molecule made by linking many monomers together.

• Four Major Classes:

  1. Carbohydrates – energy storage and structural support

  2. Lipids – long-term energy storage, membrane structure

  3. Proteins – catalysis, structure, transport, signaling

  4. Nucleic Acids – genetic information storage and transfer

• Dehydration Synthesis: The process of joining monomers by removing water to form polymers.

• Hydrolysis: Breaking polymers into monomers by adding water.

• Example: Glucose (monomer) can be joined to form starch (polymer).

Properties & Functions of Biological Macromolecules

The structure of macromolecules determines their function in biological systems. Understanding the relationship between structure and function is key to biology.

• Carbohydrates: Composed of carbon, hydrogen, and oxygen (ratio 1:2:1). Serve as energy sources and structural components. Example: cellulose in plant cell walls.

• Lipids: Include fats, oils, waxes, phospholipids, and steroids. Hydrophobic, used for energy storage and membrane structure. Example: phospholipid bilayer in cell membranes.

• Proteins: Made of amino acids. Functions include catalysis (enzymes), defense (antibodies), transport (hemoglobin), and structure (collagen).

• Nucleic Acids: DNA and RNA, composed of nucleotides. Store and transmit genetic information.

Table: Types of Chemical Bonds

Key Equations

• General formula for carbohydrates:

• Dehydration synthesis:

• Hydrolysis:

Summary

• Water's polarity and hydrogen bonding are essential for life, influencing properties like cohesion, adhesion, and surface tension.

• Life is based on a small set of elements, with carbon being central to organic molecules.

• Biological macromolecules are formed by joining monomers into polymers, with structure determining function.

• Understanding chemical bonds is crucial for explaining molecular interactions in biology.

Additional info: Some content was inferred and expanded for clarity and completeness, including definitions, examples, and equations.