Introduction to Chemistry in Anatomy & Physiology

Chemistry forms the foundation for all physiological processes in the human body. Understanding basic chemical principles is essential for comprehending how the body functions at the molecular and cellular levels.

Chemistry and Physiological Reactions

• Chemistry underlies all physiological reactions, including movement, digestion, heart function, and nervous system activity.

• Chemistry is divided into two main areas: Basic chemistry (fundamental principles) and Biochemistry (chemistry of living organisms).

Energy in Biological Systems

Kinetic and Potential Energy

• Energy is the capacity to do work or put matter into motion.

• Kinetic energy: Energy in action (e.g., muscle contraction).

• Potential energy: Stored energy (e.g., energy stored in chemical bonds).

• Energy can be transformed from potential to kinetic, such as when stored energy is released to perform work.

Forms of Energy

• Chemical energy: Stored in the bonds of chemical substances (e.g., ATP).

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

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

• Radiant (electromagnetic) energy: Travels in waves (e.g., heat, visible light, ultraviolet light, X-rays).

Atoms and Elements

Elements

• Elements are substances that cannot be broken down into simpler substances by ordinary chemical methods.

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

• Other elements are present in smaller amounts but are still essential for life.

• The periodic table lists all known elements.

Atoms

• Atoms are the smallest units of an element that retain the properties of that element.

• Atoms are unique building blocks for each element and determine the element's physical and chemical properties.

Atomic Symbol

• Each element is represented by a one- or two-letter atomic symbol (e.g., "O" for oxygen, "C" for carbon).

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

Structure of Atoms

• Atoms are composed of three subatomic particles:

  • Protons: Positive charge (+), mass = 1 atomic mass unit (amu).

  • Neutrons: No charge (0), mass = 1 amu.

  • Electrons: Negative charge (−), virtually no mass (0 amu).

Models of Atom Structure

• Planetary model: Electrons orbit the nucleus like planets around the sun.

• Orbital model: Electrons are found in a cloud around the nucleus, representing regions where they are likely to be found.

Identifying Elements

• Each element is defined by its number of protons, neutrons, and electrons.

• Atomic number: Number of protons in the nucleus (written as a subscript to the left of the atomic symbol).

• Mass number: Total number of protons and neutrons (written as a superscript to the left of the atomic symbol).

• Isotopes: Atoms of the same element with different numbers of neutrons (same atomic number, different mass number).

• Atomic weight: Average of the mass numbers of all isotope forms of an atom.

Additional info:

• Understanding atomic structure is essential for grasping how atoms interact to form molecules and compounds, which are the basis for all biological processes.