Chapter2

Chapter 2: The Chemistry of Life

Introduction to Life at the Chemical Level

• Biologists study life at multiple levels from atomic to organismal.

• The chapter focuses on chemical interactions in living organisms.

• Cells contain various chemicals that interact to produce life features.

Matter: The Building Blocks of Life

Definition of Matter

• Matter occupies space and has mass.

• Exists in three physical states:

  • Solid

  • Liquid

  • Gas

Chemical Elements

• Chemical elements are fundamental building blocks of matter.

• Elements cannot be broken down by ordinary chemical means.

• Over 100 known elements; 92 occur naturally on Earth.

• Only about 25 elements are essential for life.

  • Key elements: Oxygen (O), Carbon (C), Hydrogen (H), Nitrogen (N) account for 96% of human body weight.

  • Trace elements are necessary in smaller amounts (e.g., Iron, Iodine).

The Periodic Table

• Lists elements according to their characteristics.

• Organizes elements based on atomic number, symbol, and atomic weight.

• Includes bulk elements (most abundant) and trace elements.

Atoms: The Smallest Units of Matter

Structure of Atoms

• Atoms consist of three types of subatomic particles:

  • Protons: positive charge, mass.

  • Neutrons: no charge, mass.

  • Electrons: negative charge, nearly no mass.

• Protons and neutrons form the nucleus, while electrons orbit around it.

Atomic Number and Mass

• Atomic number: number of protons (determines element).

• Mass number: total number of protons and neutrons.

Isotopes

• Isotopes: forms of an element with the same number of protons but different neutrons.

Electron Configuration and Chemical Bonding

• Electrons dictate how an atom interacts with others.

• Electrons occupy shells, with outermost shells influencing chemical properties.

• Atoms will bond chemically to fill their electron shells (octet rule).

Types of Chemical Bonds

Ionic Bonds

• Formed when atoms transfer electrons, resulting in charged ions.

• Example: Sodium chloride (NaCl).

Covalent Bonds

• Formed when atoms share electrons.

• Types of covalent bonds:

  • Single bond (one pair of shared electrons).

  • Double bond (two pairs of shared electrons).

Water: The Foundation for Life

Structure of Water

• Composed of 2 hydrogen atoms and 1 oxygen atom (H2O).

• Water is polar due to unequal sharing of electrons.

Properties of Water

• Cohesion: water molecules stick together.

• Adhesion: water molecules cling to other substances.

• High heat capacity: absorbs energy before changing states.

• Ice floats due to lower density compared to liquid water.

• Water is an excellent solvent (aqueous solutions).

pH Scale, Acids, and Bases

Acids and Bases

• Acids: donate H+ ions (pH 0-7).

• Bases: remove H+ ions (pH 8-14).

Buffers

• Regulate pH in living systems by accepting or donating H+ ions.

Organic Molecules in Life

Definition

• Organic molecules are primarily carbon and hydrogen-based.

Carbon Chemistry

• Carbon's versatility due to its ability to form four covalent bonds.

Hydrocarbons

• Simplest organic compounds; used for energy storage.

Biological Macromolecules

Types of Macromolecules

• Carbohydrates (e.g., sugars, starches).

• Proteins (e.g., enzymes, structural proteins).

• Nucleic acids (e.g., DNA, RNA).

• Lipids (e.g., fats, phospholipids).

Carbohydrates

• Include simple sugars (monosaccharides) and complex forms (polysaccharides).

Proteins

• Composed of 20 different amino acids; essential for metabolic activities.

• Structure of proteins includes primary, secondary, tertiary, and quaternary levels.

Nucleic Acids

• Store genetic information (DNA, RNA).

Lipids

• Hydrophobic molecules important for energy storage, insulation, and cell membranes.