Chapter 02: Chemistry Comes Alive

Introduction to Chemistry in Physiology

Chemistry is fundamental to understanding physiological processes in the human body. All bodily functions, from movement to digestion and neural activity, are governed by chemical reactions. This chapter introduces the basic chemical principles essential for the study of anatomy and physiology.

Part 1 – Basic Chemistry

Matter and Energy

Matter and energy are the foundational concepts in chemistry and physiology.

• Matter: Anything that has mass and occupies space. Matter can be seen, smelled, and/or felt.

• Weight: The mass of an object plus the effects of gravity.

• States of Matter:

  • Solid: Definite shape and volume.

  • Liquid: Changeable shape; definite volume.

  • Gas: Changeable shape and volume.

• Energy: The capacity to do work or put matter into motion. Energy does not have mass or occupy space. The greater the work done, the more energy is used.

Atoms and Elements

All matter is composed of elements, which are substances that cannot be broken down into simpler substances by ordinary chemical methods.

• Major Elements of the Body: Carbon, oxygen, hydrogen, and nitrogen make up about 96% of the human body.

• Atoms: The smallest particles of an element that retain the properties of that element. Atoms are the unique building blocks for each element.

Structure of Atoms

Atoms are composed of three subatomic particles:

• Protons: Carry a positive charge (+)

• Neutrons: Have no electrical charge (0)

• Electrons: Carry a negative charge (–)

The number of protons is balanced by the number of electrons, making atoms electrically neutral. Protons and neutrons are located in the nucleus, while electrons orbit around the nucleus.

Models of Atomic Structure

There are two common models to represent atomic structure:

• Orbital Model: Shows electrons as a cloud of negative charge around the nucleus.

• Planetary Model: Depicts electrons as small spheres orbiting the nucleus.

Identifying Elements

Each element contains a unique number of subatomic particles:

• Hydrogen: 1 proton, 0 neutrons, 1 electron

• Helium: 2 protons, 2 neutrons, 2 electrons

• Lithium: 3 protons, 4 neutrons, 3 electrons

Key facts about elements include:

• Atomic Number: Number of protons in the nucleus

• Mass Number: Total number of protons and neutrons

• Isotopes: Variations of the same element with different numbers of neutrons

• Atomic Weight: Average of mass numbers of all isotope forms of an atom

Atomic Structure of the Three Smallest Atoms

Additional info: The table above summarizes the subatomic composition of the three lightest elements, which are foundational for understanding atomic structure in biological systems.