Basic Chemistry for Anatomy and Physiology

Module 2 – Basic Chemistry

Chemistry in Anatomy and Physiology

Chemistry is the scientific discipline concerned with the atomic composition and structure of substances and the reactions they undergo. It forms the foundation for understanding how the body transforms and uses energy, and how cells utilize crucial molecules such as carbohydrates, lipids, proteins, and nucleic acids.

• Role in Biology: Chemistry explains the interactions of different molecules, including energy storage and release, as seen in fat storage or enzyme-catalyzed reactions.

• Biological Relevance: Chemical reactions in the body, such as the breakdown of food, involve the movement of chemicals like ions, carbohydrates, and lipids.

Matter and Its Properties

All living and nonliving things are composed of matter, which is anything that occupies space and has mass.

• Mass: The amount of matter in an object.

• Weight: The gravitational force acting on an object of a given mass.

• States of Matter: Exists in solid, liquid, and gaseous states in the human body.

• Physical Change: Does not alter the basic nature of a substance.

• Chemical Change: Alters the composition of the substance, often substantially.

Energy and Its Forms

Energy is the capacity to do work or put matter into motion. It has no mass and does not take up space, but it can be measured by its effects on matter.

• Law of Conservation of Energy: The total energy of the universe is constant; energy is neither created nor destroyed.

Types of Energy

• Kinetic Energy: Energy of motion, displayed in the movement of particles or objects.

• Potential Energy: Stored or inactive energy.

Forms of Energy in the Body

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

• Electrical Energy: Results from the movement of charged particles (e.g., nerve impulses).

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

• Radiant Energy: Energy of electromagnetic spectrum, such as light.

Energy Conversions in the Body

In biological systems, chemical energy from food is trapped in the bonds of ATP (adenosine triphosphate), the body's energy currency.

Example: Energy and Human Life

• Carbohydrates, fats, and other chemicals are metabolized to produce ATP.

• ATP is used for cellular work, generating heat and waste products (carbon dioxide, water).

Composition of Matter

Matter is composed of a limited number of substances called elements, which cannot be broken down into simpler substances by ordinary chemical methods.

• Examples: Oxygen, silver, gold, copper, iron.

Elements and Atoms

• Element: Unique substances made of similar particles called atoms.

• Atom: The smallest unit of an element, retaining its properties.

• Atomic Symbol: One- or two-letter abbreviation for each element (e.g., C for carbon).

Atomic Structure

• Subatomic Particles:

  • Protons (p+): Positive charge

  • Neutrons (n0): No charge

  • Electrons (e-): Negative charge, equal in strength to the positive charge of protons

• Planetary Model: Atom as a miniature solar system with protons and neutrons in the nucleus, electrons in orbits (electron cloud).

Atomic Number and Mass

• Atomic Number: Number of protons in the nucleus; also equals the number of electrons in a neutral atom.

• Atomic Mass Number: Sum of protons and neutrons in the nucleus.

Isotopes and Atomic Weight

• Isotopes: Atoms of the same element with the same number of protons and electrons but different numbers of neutrons.

• Atomic Weight: Average mass of all isotopes of an element.

Common Elements Making Up the Human Body

The following table summarizes the major elements found in the human body, their atomic symbols, and their approximate percentage by body weight.

Element	Atomic Symbol	Percentage of Body Weight	Role in the Body
Oxygen	O	65.0	Major component of organic and inorganic molecules; essential for cellular respiration.
Carbon	C	18.5	Primary element of all organic molecules, including carbohydrates, lipids, proteins, and nucleic acids.
Hydrogen	H	9.5	Component of water and most organic molecules; influences pH of body fluids.
Nitrogen	N	3.2	Component of proteins and nucleic acids (genetic material).
Calcium	Ca	1.5	Found in bones and teeth; required for muscle contraction, nerve impulses, and blood clotting.
Phosphorus	P	1.0	Part of ATP, nucleic acids, and bones/teeth.
Potassium	K	0.4	Major intracellular cation; necessary for nerve function and muscle contraction.
Sulfur	S	0.3	Component of some proteins (e.g., muscle proteins).
Sodium	Na	0.2	Major extracellular cation; important for water balance, nerve function, and muscle contraction.
Chlorine	Cl	0.2	Major extracellular anion; important for water balance and nerve function.
Magnesium	Mg	0.1	Component of many enzymes; important for metabolic reactions.
Iodine	I	0.1	Needed for synthesis of thyroid hormones.
Iron	Fe	0.1	Component of hemoglobin (oxygen transport in blood) and some enzymes.

Additional info: Trace elements (less than 0.01% of body mass) are also essential for health, including zinc, copper, selenium, and others.