Chapter 2: Chemistry of Life – Foundations for Anatomy & Physiology

Chapter 2: Chemistry of Life

General Overview

This chapter introduces the chemical principles essential for understanding biological processes in Anatomy & Physiology. It covers the nature of matter, atomic structure, chemical bonds, and the properties of molecules relevant to living systems.

Intro to Chemistry

Key Terms and Concepts

• Chemistry: The study of chemicals and their changes, especially those occurring during chemical reactions.

• Matter: Anything that takes up space and has mass. All organisms are composed of matter, which cycles through the environment and is transformed but not created or destroyed.

• Elements: Substances that cannot be broken down by chemical reactions. They are the building blocks of matter.

• Compounds: Substances formed from two or more different elements in a fixed ratio (e.g., H2O, NaCl).

• Molecules: Two or more atoms held together by chemical bonds. All compounds are molecules, but not all molecules are compounds.

Three Forms of Matter

• Solids: Atoms are tightly bound, forming a fixed shape (e.g., ice).

• Liquids: Atoms are closely bound but not rigid, no fixed shape (e.g., water).

• Gases: Particles are well spaced, no fixed shape or volume, and can be compressed (e.g., water vapor).

Elements of Life

Main Elements in Living Organisms

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

• Other Important Elements: Phosphorus (P), Sulfur (S) – essential for biochemical processes.

• Trace Elements: Required in minute quantities (less than 0.01% of body mass), such as calcium (Ca), potassium (K), sodium (Na), iron (Fe).

Atoms and Their Structure

• Atom: The smallest unit of matter that retains the properties of an element.

• Subatomic Particles:

  • Protons: Positively charged, located in the nucleus.

  • Neutrons: Neutral charge, located in the nucleus.

  • Electrons: Negatively charged, orbit the nucleus in the valence shell.

• Atomic Number: Number of protons; defines the element.

• Mass Number (Atomic Mass): Number of protons plus neutrons.

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

Chemical Bonds

Types of Chemical Bonds

• Ionic Bonds: Formed when one atom donates or accepts electrons, resulting in charged ions (cations and anions) that attract each other. Example: Table salt (NaCl) – sodium donates an electron to chlorine.

• Covalent Bonds: Formed when atoms share electrons. Single, Double, Triple Bonds: Sharing one, two, or three pairs of electrons, respectively.

• Hydrogen Bonds: Weak attractions between a hydrogen atom (partial positive) and an electronegative atom (partial negative, such as oxygen or nitrogen) in another molecule. Importance: Stabilizes large biological molecules (e.g., DNA, proteins).

Bond Polarity and the Octet Rule

• Polar Covalent Bonds: Electrons are shared unequally due to differences in electronegativity (e.g., H2O).

• Non-Polar Covalent Bonds: Electrons are shared equally (e.g., O2, CH4).

• Octet Rule: Atoms tend to form bonds to achieve eight electrons in their valence shell.

Chemical Reactions

Basic Principles

• Chemical Reaction: Making and breaking of chemical bonds, involving reactants (starting materials) and products (ending materials).

• Metabolism: The sum of all chemical reactions in the body.

• Examples:

  • Photosynthesis: $\text{6 CO}_2 + \text{6 H}_2\text{O} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + \text{6 O}_2$

  • Cellular Respiration: $\text{C}_6\text{H}_{12}\text{O}_6 + \text{6 O}_2 \rightarrow \text{6 CO}_2 + \text{6 H}_2\text{O}$

• Chemical Equilibrium: The point at which forward and reverse reactions occur at equal rates, with no net change in concentrations of reactants and products.

Summary Table: Key Terms and Definitions

Term	Definition	Example
Element	Pure substance, cannot be broken down	Oxygen (O)
Compound	Two or more different elements in fixed ratio	Water (H2O)
Molecule	Two or more atoms bonded together	O2, H2O
Atom	Smallest unit of an element	Helium (He)
Ion	Charged atom or molecule	Na+, Cl-
Isotope	Atom with same number of protons, different neutrons	Carbon-12, Carbon-14

Review Questions

1. What is matter, and what are the three forms of matter?

2. How do elements, compounds, and molecules differ?

3. What are the top elements essential for life, and what are trace elements?

4. Describe the structure of an atom and the significance of atomic number, mass number, and isotopes.

5. Explain the differences between ionic, covalent, and hydrogen bonds.

6. What is the difference between polar and non-polar covalent bonds?

7. How do chemical reactions relate to metabolism, and what is chemical equilibrium?

Additional info: These notes expand on the provided slides by including definitions, examples, and academic context for each major concept, ensuring a comprehensive understanding suitable for Anatomy & Physiology students.