Chemistry of Life

Introduction

The chemistry of life explores the atomic and molecular foundations that underpin biological processes. Understanding atoms, elements, compounds, and chemical bonds is essential for studying biology at the molecular level.

Definitions and Key Concepts

• Matter: Anything that has mass and occupies space.

• Element: A pure substance consisting of only one type of atom, distinguished by its atomic number.

• Compound: A substance formed when two or more elements are chemically bonded together.

• Major Elements in Living Matter: Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N) make up about 96% of living matter.

• Essential Element: An element required for an organism to survive, grow, and reproduce.

• Trace Element: An element required by an organism in minute quantities (e.g., Iron (Fe), Iodine (I)).

Atomic Structure

• Atom: The smallest unit of an element, retaining its chemical properties.

• Subatomic Particles:

  • Proton: Positively charged particle in the nucleus.

  • Neutron: Neutral particle in the nucleus.

  • Electron: Negatively charged particle orbiting the nucleus.

• Atomic Number: Number of protons in the nucleus of an atom.

• Mass Number: Sum of protons and neutrons in the nucleus.

• Atomic Nucleus: Central part of the atom containing protons and neutrons.

• Electron Location: Electrons are found in energy levels (shells) surrounding the nucleus.

• Energy: The capacity to do work or cause change.

• Potential Energy: Stored energy due to position or arrangement.

Periodic Table and Element Identification

• Periodic Table: Organizes elements by increasing atomic number and chemical properties.

• Element Example: Carbon (C), atomic number 6, atomic mass 12.011.

• Valence Electrons: Electrons in the outermost shell, important for chemical bonding.

Isotopes

• Isotope: Atoms of the same element with different numbers of neutrons.

• Radioactive Isotope: An isotope that decays spontaneously, emitting radiation.

• Application: Radioactive isotopes are used in medical imaging and cancer treatment.

Chemical Bonds

• Covalent Bond: A chemical bond formed by the sharing of electron pairs between atoms.

• Non-polar Covalent Bond: Electrons are shared equally between atoms.

• Polar Covalent Bond: Electrons are shared unequally, creating partial charges.

• Ionic Bond: Formed when one atom transfers electrons to another, resulting in oppositely charged ions.

• Anion: Negatively charged ion.

• Cation: Positively charged ion.

• Hydrogen Bond: Weak bond between a hydrogen atom and an electronegative atom (e.g., oxygen or nitrogen).

• Electronegativity: The ability of an atom to attract electrons in a covalent bond.

Structural and Molecular Formulas

• Molecular Formula: Shows the types and numbers of atoms in a molecule (e.g., for water).

• Structural Formula: Shows the arrangement of atoms and bonds (e.g., O=O for oxygen gas).

Table: Molecule and Compound Classification

Photosynthesis

• Photosynthesis Equation:

• Reactants: Carbon dioxide and water

• Products: Glucose and oxygen

Properties of Water

• Cohesion: Water molecules stick to each other due to hydrogen bonding.

• Adhesion: Water molecules stick to other surfaces.

• Ice Floats: Ice is less dense than liquid water because hydrogen bonds hold water molecules apart in a crystalline structure.

• Hydrogen Bonds in Ice vs. Liquid Water: In ice, hydrogen bonds are stable and form a lattice; in liquid water, bonds constantly break and reform.

Solutions and pH

• Aqueous Solution: A solution in which water is the solvent.

• pH Scale: Measures the concentration of hydrogen ions () in a solution. Ranges from 0 (acidic) to 14 (basic).

• Buffer: A substance that minimizes changes in pH by accepting or donating ions.

Table: Buffer Action

Ocean Acidification

• Process: When dissolves in seawater, it forms carbonic acid (), which lowers ocean pH.

• Impact: Lower pH affects marine organisms, especially those that build shells from calcium carbonate.

• Equations:

• Application: Ocean acidification threatens coral reefs and shell-forming marine life.

Summary Table: Key Terms and Definitions

Additional info: Some explanations and table entries have been expanded for clarity and completeness, including inferred molecular structures and applications.