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

Matter and Its States

Definition and Properties of Matter

Matter is a fundamental concept in chemistry and physiology, referring to anything that occupies space and has mass (weight). All living and non-living things are composed of matter.

• Solid: Has a definite shape and volume.

• Liquid: Has a definite volume but a changeable shape.

• Gas: Has both changeable shape and volume.

Example: Bones are solids, blood is a liquid, and oxygen in the lungs is a gas.

Energy in Biological Systems

Definition and Types of Energy

Energy is the capacity to do work or put matter into motion. In physiology, energy is essential for all cellular and bodily functions.

• Kinetic energy: Energy in action; active energy that is currently causing change (e.g., muscle contraction).

• Potential energy: Stored (inactive) energy; becomes kinetic when released (e.g., energy stored in chemical bonds).

Forms of Energy

• Chemical energy: Stored in the bonds of chemical substances, such as ATP (adenosine triphosphate).

• Electrical energy: Results from movement of charged particles, such as ions across cell membranes.

• Mechanical energy: Directly involved in moving matter, such as muscle movement.

• Radiant or electromagnetic energy: Exhibits wavelike properties, including visible light, ultraviolet light, and X-rays.

Example: Nerve impulses are electrical energy; muscle contraction is mechanical energy.

Energy Form Conversions

Energy can be converted from one form to another in biological systems, but conversion is often inefficient, with some energy lost as heat.

• Food converted to ATP: Chemical energy from food is transformed into ATP, the cell's energy currency.

• Heat production: Muscle contraction produces heat, helping to maintain body temperature.

Atoms: The Building Blocks of Matter

Atomic Structure

Atoms are the smallest stable units of matter and are composed of subatomic particles. Understanding atomic structure is essential for grasping chemical reactions in physiology.

• Protons (p+): Positively charged particles located in the nucleus.

• Neutrons (n0): Electrically neutral particles also found in the nucleus.

• Electrons (e-): Negatively charged particles that whirl around the nucleus, forming the electron cloud.

The number of electrons in an atom always equals the number of protons, resulting in electrical neutrality.

Models of Atomic Structure

• Orbital model: Represents electrons as a cloud of negative charge around the nucleus.

• Simplified model: Shows electrons as small spheres orbiting the nucleus.

Example: Hydrogen atom has 1 proton and 1 electron; helium has 2 protons, 2 neutrons, and 2 electrons.

Subatomic Particle	Charge	Location
Proton (p+)	+1	Nucleus
Neutron (n0)	0	Nucleus
Electron (e-)	-1	Electron cloud

Additional info: Atomic structure is foundational for understanding chemical bonding, reactions, and the molecular basis of physiological processes.

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