Chapter 2: The Chemical Foundation of Life

Introduction

• Matter is the substance that makes up all life.
• Matter has mass and is composed of atoms.
• Atoms are the smallest unit of matter with distinct chemical and physical properties.

Elements and Atoms

• Elements are determined by the number of protons.
• Chemical symbols are used as shorthand for elements.
• Four most common elements in living organisms: Carbon (C), Hydrogen (H), Nitrogen (N), Oxygen (O) — known as CHON.

Structure of an Atom

• Atoms consist of subatomic particles: protons, neutrons, and electrons.
• Nucleus: Center of an atom, contains protons (+ charge) and neutrons (no charge).
• Electrons: Negatively charged, found in orbitals around the nucleus.
• Protons and neutrons contribute to atomic mass.

Isotopes

• Isotopes are variants of elements with different numbers of neutrons.
• Example: Carbon-12, Carbon-13, and Carbon-14.
• Used in various dating techniques like carbon dating.

Periodic Table

• Organizes elements by atomic number (number of protons).
• Periodic table shows chemical behavior patterns.
• Common elements in living things are smaller and found at the top of the table.

Electron Shells and Energy Levels

• Electrons are distributed in energy levels around the nucleus.
• First energy level: Can hold up to 2 electrons.
• Octet Rule: Subsequent energy levels can hold up to 8 electrons.
• Valence Shell: Outermost shell, determines chemical reactivity.

Chemical Bonds

• Covalent Bonds: Electrons are shared between atoms.
  • Can be single, double, or triple bonds.
  • Polar Covalent Bonds: Unequal sharing of electrons.
  • Non-polar Covalent Bonds: Equal sharing of electrons.
• Ionic Bonds: Form between oppositely charged ions.
• Hydrogen Bonds: Weak attractions, important in water interactions.

Chemical Reactions

• Involves rearrangement of electrons and atoms.
• Reactants convert to products.
• Can be reversible or irreversible.

Properties of Water

• Water's polarity allows it to form hydrogen bonds.
• Cohesion: Water molecules stick to each other.
• Adhesion: Water molecules stick to other substances.
• High Heat Capacity: Water can absorb large amounts of heat with little temperature change.
• Evaporative Cooling: Water absorbs heat when it evaporates.
• Solvent Properties: Water is a good solvent due to its polarity.

pH and Buffers

• pH Scale: Measures acidity or basicity, ranges from 0-14.
• Neutral pH: 7, equal H+ and OH- ions.
• Buffers: Maintain pH balance in solutions, important in biological systems.

Organic Chemistry

• Carbon: Central element in organic compounds.
• Can form diverse structures: Chains, rings.
• Functional Groups: Chemical groups that attach to carbon skeletons, impart specific properties.

Conclusion

• Understanding chemical principles is essential for biology.
• Water and carbon are fundamental to life processes.
• Explore the interactions and properties of elements and molecules in living organisms.