Fundamentals of Anatomy & Physiology: Chemical and Cellular Basis, Tissues, and Cell Types

Chemical Basis of Life

Atoms & Elements

Atoms are the basic units of matter, composed of protons, neutrons, and electrons. Elements are substances made of only one type of atom.

• Proton (p+): Positively charged particle in the nucleus; determines atomic number and element identity.

• Neutron (n): Neutral particle in the nucleus; contributes to atomic mass.

• Electron (e-): Negatively charged particle orbiting the nucleus; involved in chemical bonding.

• Atomic Number: Number of protons in an atom.

• Atomic Mass: Sum of protons and neutrons.

• Isotopes: Atoms of the same element with different numbers of neutrons.

Example: Carbon-12 and Carbon-14 are isotopes of carbon.

Compounds & Molecules

Compounds are substances formed from two or more different elements bonded together. Molecules are groups of atoms bonded together.

• Compound: H2O (water), NaCl (sodium chloride)

• Molecule: O2 (oxygen gas)

Valence Electrons

Valence electrons are electrons in the outermost shell of an atom, crucial for chemical bonding.

• Atoms tend to gain, lose, or share electrons to achieve a stable configuration (octet rule).

Chemical Bonds

Ionic Bonds

Ionic bonds form when electrons are transferred from one atom to another, creating charged ions.

• Cation: Positively charged ion (e.g., Na+).

• Anion: Negatively charged ion (e.g., Cl-).

• Example: Sodium chloride (NaCl) forms from Na+ and Cl-.

Covalent Bonds

Covalent bonds form when atoms share electrons. They can be polar or non-polar.

• Polar Covalent: Unequal sharing of electrons (e.g., H2O).

• Non-Polar Covalent: Equal sharing of electrons (e.g., O2).

Hydrogen Bonds

Hydrogen bonds are weak attractions between a hydrogen atom in one molecule and an electronegative atom (like oxygen or nitrogen) in another.

• Important in water, DNA, and protein structure.

Water and Its Properties

Water Molecule

Water (H2O) is a polar molecule with unique properties essential for life.

• High heat capacity

• Solvent for many substances

• Participates in chemical reactions

Biological Molecules

Proteins

Proteins are polymers of amino acids and perform structural, enzymatic, and regulatory functions.

• Monomer: Amino acid

• Polymer: Polypeptide

• Structure: Primary, secondary, tertiary, quaternary

• Examples: Collagen (structural), hemoglobin (transport)

Carbohydrates

Carbohydrates are sugars and starches that provide energy and structural support.

• Monosaccharides: Simple sugars (glucose, fructose)

• Disaccharides: Two sugars (sucrose)

• Polysaccharides: Many sugars (glycogen, starch)

Lipids

Lipids are hydrophobic molecules used for energy storage, insulation, and cell membrane structure.

• Types: Triglycerides, phospholipids, steroids

• Example: Cholesterol (steroid), phospholipid (membrane)

Nucleic Acids

Nucleic acids (DNA and RNA) store and transmit genetic information.

• Monomer: Nucleotide

• Polymer: DNA, RNA

Cell Structure and Function

Cell Membrane

The cell membrane is a phospholipid bilayer that controls the movement of substances in and out of the cell.

• Components: Phospholipids, proteins, cholesterol

• Functions: Protection, communication, transport

Organelles

Organelles are specialized structures within cells that perform specific functions.

• Nucleus: Contains DNA

• Mitochondria: Produces ATP via cellular respiration

• Ribosomes: Protein synthesis

• Endoplasmic Reticulum: Protein and lipid synthesis

• Golgi Apparatus: Modifies and packages proteins

Fluid Compartments

Body fluids are divided into intracellular (inside cells) and extracellular (outside cells) compartments.

• Intracellular Fluid (ICF): Cytoplasm

• Extracellular Fluid (ECF): Plasma, interstitial fluid

Tissues of the Human Body

Epithelial Tissue

Epithelial tissue lines body surfaces and cavities, providing protection, secretion, and absorption.

• Simple Epithelium: Single layer, absorption/exchange (lungs)

• Stratified Epithelium: Multiple layers, protection (skin)

• Glandular Epithelium: Secretion (glands)

Connective Tissue

Connective tissue supports, protects, and stores energy.

• Loose Connective Tissue: Areolar (protects organs), adipose (stores fat)

• Dense Connective Tissue: Tendons (muscle to bone), ligaments (bone to bone)

• Bone: Osteocytes, collagen fibers

• Cartilage: Firm, flexible support

Muscle Tissue

Muscle tissue enables movement through contraction.

• Types: Skeletal (voluntary), cardiac (heart), smooth (involuntary)

Neural Tissue

Neural tissue transmits electrical signals and processes information.

• Neurons: Conduct impulses

• Neuroglia: Support neurons

Cell Death and Stem Cells

Cell Death

Cells can die due to injury, lack of oxygen, or programmed cell death (apoptosis).

• Necrosis: Death due to damage

• Hypoxia: Lack of oxygen

• Ischemia: Lack of blood supply

• Apoptosis: Programmed cell death

Stem Cells

Stem cells are undifferentiated cells capable of dividing and developing into specialized cell types.

• Function: Tissue repair, growth, regeneration

Acids, Bases, and pH

Acids & Bases

Acids release hydrogen ions (H+), while bases accept them. pH measures the concentration of H+ ions.

• Acid: pH < 7

• Base: pH > 7

• Neutral: pH = 7

Formula:

$\text{pH} = -\log_{10}[\text{H}^+]$

Summary Table: Major Tissue Types

Tissue Type	Main Function	Key Features	Examples
Epithelial	Protection, secretion, absorption	Cells tightly packed, lines surfaces	Skin, glands, lining of gut
Connective	Support, storage, protection	Cells in matrix, fibers present	Bone, cartilage, blood, adipose
Muscle	Movement	Contractile cells	Skeletal, cardiac, smooth muscle
Neural	Signal transmission	Neurons and supporting cells	Brain, spinal cord, nerves

Additional info: Some explanations and examples have been expanded for clarity and completeness, such as the functions of organelles and tissue types.