Chapter 2: Chemistry Comes Alive – Foundations for Anatomy & Physiology

Part I: Chemistry Comes Alive

Introduction

This chapter introduces the essential chemical principles that underpin the study of Anatomy & Physiology. Understanding matter, energy, elements, chemical bonds, compounds, mixtures, and chemical reactions is crucial for comprehending biological processes in the human body.

Matter and Its States

Definition and Properties

Matter is anything that has mass and occupies space. It is the physical substance of the universe, including all living and non-living things.

• Mass: The measure of the amount of matter in an object.

• Matter exists in three primary states:

  • Solid: Has a definite shape and volume.

  • Liquid: Has volume but conforms to the shape of its container.

  • Gas: Has neither definite shape nor volume; expands to fill its container.

Energy in Biological Systems

Definition and Forms

Energy is the capacity to do work or put matter into motion. Unlike matter, energy does not have mass or occupy space.

• The more work done, the more energy is used.

• Energy exists in two basic forms:

  • Kinetic Energy: Energy in action or motion.

  • Potential Energy: Stored (inactive) energy that can be released to do work.

• Energy can be transformed from one form to another.

Types of Energy Relevant to Physiology

• Chemical Energy: Stored in the bonds of chemical substances; released during chemical reactions (e.g., ATP hydrolysis).

• Electrical Energy: Results from movement of charged particles; essential for nerve impulse transmission.

• Mechanical Energy: Directly involved in moving matter; e.g., muscle contraction.

• Radiant or Electromagnetic Energy: Travels in waves; includes heat, visible light, and ultraviolet light.

Example: The nervous system uses electrical energy to generate nerve impulses.

Energy Conversion and Efficiency

• Energy may be converted from one form to another, but it cannot be created or destroyed (Law of Conservation of Energy).

• Example: Turning on a lamp converts electrical energy to light energy.

• Energy conversions are inefficient; some energy is "lost" as heat, which is partly unusable.

• Heat generated by energy conversions in the body helps maintain body temperature.

Properties of Elements

Definition and Classification

Elements are substances that cannot be broken down into simpler substances by ordinary chemical methods. They are the building blocks of matter.

• Elements make up all matter, including the human body.

• Four elements make up 96% of body weight: Carbon (C), Oxygen (O), Hydrogen (H), and Nitrogen (N).

• Other elements (Phosphorus, Potassium, Sulfur, Sodium, Chlorine, Magnesium, Iron) make up 3.9% of body weight.

• Trace elements make up less than 0.01% of body weight but are essential for health.

• The Periodic Table lists all known elements.

Atomic Structure

• Elements are made up of atoms, the smallest unit of matter retaining the properties of the element.

• Each atom has a unique atomic symbol (e.g., "O" for oxygen, "C" for carbon).

• Some symbols are derived from Latin names (e.g., "Na" for sodium from natrium).

Summary Table: Major Elements in the Human Body

Element	Symbol	Body Weight (%)	Function/Location
Oxygen	O	65	Component of water and organic molecules; needed for cellular respiration
Carbon	C	18.5	Component of all organic molecules (carbohydrates, lipids, proteins, nucleic acids)
Hydrogen	H	9.5	Component of water and most organic molecules
Nitrogen	N	3.2	Component of proteins and nucleic acids
Phosphorus	P	1.0	Component of nucleic acids and ATP
Calcium	Ca	1.5	Found in bones and teeth; important for muscle contraction
Potassium	K	0.4	Major cation in cells; necessary for nerve function
Sodium	Na	0.2	Major cation in extracellular fluid; important for water balance
Iron	Fe	Trace	Component of hemoglobin in blood
Magnesium	Mg	0.1	Required for enzyme activity

Additional info: Table values inferred from standard human body composition data.