Biochemistry Foundations for Anatomy & Physiology

Biochemistry and Its Relevance to Anatomy & Physiology

Introduction to Biochemistry in A&P

Biochemistry is the study of the chemical processes and substances that occur within living organisms. In Anatomy & Physiology (A&P), understanding biochemistry is essential because biochemical molecules form the basis of life and underpin cellular structure and function.

• Biochemical molecules include carbohydrates, lipids, proteins, and nucleic acids.

• These molecules are fundamental to cytology (study of cells), histology (study of tissues), and physiology (study of function).

Key Elements: Most biochemical molecules are composed of the elements C (carbon), H (hydrogen), O (oxygen), N (nitrogen), and P (phosphorus).

Structure of Atoms

Subatomic Particles

Atoms are the basic units of matter, consisting of subatomic particles: protons, neutrons, and electrons.

Particle	Charge	Mass (amu = atomic mass unit)
Proton (p+)	+1	1 amu
Neutron (n0)	0	1 amu
Electron (e-)	-1	~0 (0.0005 amu)

Atomic Structure and Notation

• Protons and neutrons are located in the nucleus; electrons orbit the nucleus.

• The atomic number is the number of protons in the nucleus and is shown as a subscript to the left of the atomic symbol.

• The mass number is the total number of protons and neutrons, shown as a superscript to the left of the atomic symbol.

• Example: For carbon: Atomic number: 6 Mass number: 12 Symbol: C

Isotopes and Atomic Weight

Isotopes are structural variations of the same element, differing in the number of neutrons.

• Atomic weight is the average of mass numbers of all isotopes of an atom.

• Example: Hydrogen has three isotopes: Hydrogen (¹H): 0 neutrons Deuterium (²H): 1 neutron Tritium (³H): 2 neutrons

Elements and Compounds

Definitions

• Elements are pure substances that cannot be broken down by chemical means.

• Compounds are substances formed when two or more elements chemically combine in fixed proportions.

• A molecule is a general term for two or more atoms bonded together; a compound is a specific molecule that has two or more different kinds of atoms bonded together.

Atomic Models

Planetary Model

• A simplified and outdated model that depicts electrons in fixed circular paths around the nucleus.

• Useful for illustration but not accurate for describing electron behavior.

Orbital Model

• The current model shows electrons in probable regions (orbitals) where they are likely to be found, rather than fixed paths.

Chemical Bonds: Role of Electrons

Electron Shells and Valence Electrons

Chemical bonds are the forces that hold atoms together in molecules and compounds. Electrons occupy areas around the nucleus called electron shells.

• Each shell contains electrons with specific energy levels.

• The valence shell is the outermost electron shell and contains electrons involved in chemical reactions.

• Electrons in the valence shell have the most potential energy and are farthest from the nucleus.

Periodic Table and Electron Configuration

• The periodic table organizes elements by atomic number and electron configuration.

• Inner shells fill first; the outermost shell determines chemical reactivity.

Additional info: The octet rule states that atoms tend to gain, lose, or share electrons to achieve a full valence shell, typically with eight electrons (except for hydrogen and helium).