Chapter 2: Basic Chemistry for Anatomy & Physiology

Chapter 2: Basic Chemistry

Focus and Overview

This chapter introduces the foundational chemical principles essential for understanding Anatomy & Physiology. Key topics include the structure of matter, types of energy, atomic structure, chemical bonds, and chemical reactions.

• Levels of organization

• Subatomic particles of an atom

• Bonds and chemical reactions

• Water polarity and properties

• Inorganic/organic compounds

• pH scale

• Molecules and macromolecules

• Protein structure and denaturation

• Enzyme function

• DNA and ATP importance

Matter and Energy

Matter

Matter is anything that occupies space and has mass. It exists in three states: solid, liquid, and gas. Matter can change:

• Physically: Changes that do not alter the chemical composition (e.g., melting ice).

• Chemically: Changes that alter the chemical composition (e.g., burning wood).

Energy

Energy is the capacity to do work or cause change. It exists in two main forms:

• Kinetic energy: Energy in motion (e.g., moving car).

• Potential energy: Stored energy due to position or structure (e.g., chemical bonds).

Types of Energy

• Chemical: Stored in chemical bonds (e.g., ATP in cells).

• Electrical: Movement of charged particles (e.g., nerve impulses).

• Mechanical: Directly involved in moving matter (e.g., muscle contraction).

• Radiant: Travels in waves (e.g., sunlight).

Example: ATP (adenosine triphosphate) is the main energy currency in cells, storing and releasing energy as needed.

Composition of Matter

Elements and Atoms

Elements are pure substances that cannot be broken down by ordinary means. Atoms are the smallest units of elements, composed of subatomic particles:

• Protons: Positively charged, in the nucleus

• Neutrons: No charge, in the nucleus

• Electrons: Negatively charged, orbit the nucleus

Major Elements in the Human Body

Element	Symbol	Body %
Oxygen	O	65%
Carbon	C	18.5%
Hydrogen	H	9.5%
Nitrogen	N	3.2%

Other elements (e.g., calcium, phosphorus, potassium, sulfur, sodium, chlorine, magnesium, iodine, iron) are present in smaller amounts but are essential for life.

Atomic Structure

• Atoms are electrically neutral when protons = electrons.

• Electrons occupy energy levels (shells) around the nucleus.

• Valence electrons (outermost shell) determine chemical reactivity.

Isotopes and Radioactivity

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

• Radioisotopes: Unstable isotopes that decay, emitting radiation (used in medical imaging).

Chemical Bonds and Chemical Reactions

Chemical Bonds

Chemical bonds are forces that hold atoms together in molecules and compounds. Main types include:

Bond Type	Description	Example
Ionic	Transfer of electrons from one atom to another; forms ions	NaCl (table salt)
Covalent	Sharing of electrons between atoms	H2O (water)
Hydrogen	Weak attraction between a hydrogen atom and an electronegative atom	Between water molecules

Chemical Reactions

Chemical reactions involve making or breaking bonds between atoms. Main types include:

• Synthesis (Combination): $A + B \rightarrow AB$ (e.g., protein synthesis)

• Decomposition: $AB \rightarrow A + B$ (e.g., digestion of food)

• Exchange: $AB + CD \rightarrow AD + CB$

Energy is absorbed or released during chemical reactions. Synthesis reactions are anabolic (build up), while decomposition reactions are catabolic (break down).

Additional Key Concepts

Water and Its Properties

• Polarity: Water is a polar molecule, allowing it to dissolve many substances.

• Unique Properties: High heat capacity, cohesion, adhesion, excellent solvent.

pH Scale

The pH scale measures hydrogen ion concentration in a solution:

• Acidic: pH < 7

• Neutral: pH = 7

• Basic (alkaline): pH > 7

Organic and Inorganic Compounds

• Organic compounds: Contain carbon; include carbohydrates, lipids, proteins, nucleic acids.

• Inorganic compounds: Do not contain carbon; include water, salts, acids, bases.

Macromolecules and Biological Importance

• Proteins: Made of amino acids; structure, function, and regulation of tissues and organs.

• Denaturation: Loss of protein structure (and function) due to heat or pH changes.

• Enzymes: Biological catalysts that speed up chemical reactions.

• DNA: Genetic material; stores instructions for protein synthesis.

• ATP: Main energy carrier in cells.

Summary Table: Types of Chemical Bonds

Bond Type	Strength	Example
Ionic	Strong (in dry state)	NaCl
Covalent	Strong	H2O
Hydrogen	Weak	Between DNA strands

Additional info: This summary expands on the provided notes with definitions, examples, and academic context to ensure clarity and completeness for Anatomy & Physiology students.