Anatomy, Physiology, and Cell Biology Vocabulary

Cell Metabolism

The sum of all chemical reactions carried out by a cell to maintain life, including anabolic, catabolic, and oxidation-reduction reactions.

Anabolic Reactions

Building chemical reactions in which smaller molecules are bonded together to form larger macromolecules, requiring energy.

Catabolic Reactions

Chemical reactions that break down macromolecules into smaller constituent molecules, releasing energy.

Plasma Membrane

A selectively permeable phospholipid bilayer surrounding each cell that isolates internal structures and defines the intracellular space.

Cytosol

The intracellular fluid (ICF) consisting mostly of water with dissolved solutes, inclusions, and proteins.

Organelles

Specialized cellular structures suspended in cytosol that perform specific metabolic functions and achieve compartmentalization.

Cytoskeleton

A network of protein filaments that creates and maintains cell shape, holds organelles in place, and enables intracellular transport.

Fluid Mosaic Model

Model describing the plasma membrane as a dynamic fluid structure composed of phospholipids, proteins, lipids, and carbohydrates.

Integral Proteins

Membrane proteins that span the entire width of the phospholipid bilayer, also known as transmembrane proteins.

Peripheral Proteins

Membrane proteins attached to only one side or surface of the plasma membrane bilayer.

Selective Permeability

The property of the phospholipid bilayer that allows certain substances to cross while prohibiting the passage of others.

Concentration Gradient

A difference in solute concentration between two compartments that acts as a driving force for passive transport.

Diffusion

The passive movement of solute molecules from an area of higher concentration to lower concentration until equilibrium is reached.

Simple Diffusion

A passive transport process where nonpolar solutes pass directly through the phospholipid bilayer without membrane proteins.

Facilitated Diffusion

A passive transport process where charged or polar solutes cross the membrane with the assistance of channel or carrier proteins.

Osmosis

The passive movement of a solvent (usually water) across a selectively permeable membrane toward a higher solute concentration.

Aquaporins

Transmembrane channel proteins that serve as the primary route for water movement across the plasma membrane during osmosis.

Isotonic Solution

A solution having the same solute concentration as the cytosol, resulting in no net water movement or cell volume change.

Hypertonic Solution

A solution having a higher solute concentration than the cytosol, drawing water out of the cell and causing it to crenate.

Hypotonic Solution

A solution having a lower solute concentration than the cytosol, drawing water into the cell and causing it to swell or lyse.

Primary Active Transport

Direct ATP-requiring transport mechanism that moves solutes against their concentration gradient using carrier pumps.

Sodium-Potassium Pump ($Na^+/K^+$ Pump)

A primary active transport pump that maintains ion homeostasis by moving $3\,Na^+$ out of the cell and $2\,K^+$ into the cell per hydrolyzed ATP.

Secondary Active Transport

An indirect active transport process where the concentration gradient established by primary active transport powers the movement of another solute.

Phagocytosis

A form of endocytosis ('cell eating') in which a cell ingests large particles, bacteria, or cell debris via a phagosome.

Pinocytosis

A form of endocytosis ('cell drinking') where a cell engulfs droplets of extracellular fluid containing dissolved solutes.

Receptor-Mediated Endocytosis

A specialized form of pinocytosis in which specific ligands bind membrane receptors in protein-coated pits to form transport vesicles.

Exocytosis

An active transport process in which intracellular vesicles fuse with the plasma membrane to secrete substances into the extracellular fluid.

Transcytosis

A process where molecules enter a cell via endocytosis, are transported across the cytoplasm, and are released on the opposite side by exocytosis.

Mitochondria

Double-membrane organelles with internal cristae folds that produce most of the cell's ATP via aerobic cellular respiration.

Free Ribosomes

Unattached ribosomes floating in the cytosol that synthesize soluble proteins functioning within the cell interior.

Membrane-Bound Ribosomes

Ribosomes attached to the rough endoplasmic reticulum that synthesize proteins destined for membranes, lysosomes, or export.

Rough Endoplasmic Reticulum (RER)

A membrane-bound organelle studded with ribosomes that serves as a membrane factory and site of secretory protein assembly.

Smooth Endoplasmic Reticulum (SER)

A tubular organelle continuous with RER that catalyzes lipid metabolism, cholesterol synthesis, drug detoxification, and calcium storage.

Golgi Apparatus

Stacked, flattened membranous sacs that receive, modify, package, and ship proteins and lipids from the endoplasmic reticulum.

Lysosomes

Acidic membranous vesicles containing hydrolytic digestive enzymes that recycle cell waste and degrade nonfunctional organelles.

Peroxisomes

Membranous sacs containing oxidases and catalases that neutralize free radicals, detoxify harmful chemicals, and break down fatty acids.

Microfilaments

The smallest cytoskeletal fibers, composed of actin proteins, that support microvilli, form the terminal web, and function in cytokinesis.

Intermediate Filaments

Rope-like cytoskeletal fibers (such as keratin) that provide structural stability, maintain cell shape, and anchor cellular junctions.

Microtubules

The largest cytoskeletal fibers, composed of tubulin subunits, that form structural tracks for intracellular transport, centrioles, and cilia.

Centrioles

A pair of short, hollow microtubule cylinders located within the centrosome that assemble the mitotic spindle during cell division.

Cilia

Hair-like cell surface projections containing microtubule doublets that beat rhythmically to propel fluids or mucus across the cell surface.

Nucleolus

A dark-staining, non-membrane bound nuclear region responsible for the synthesis and assembly of ribosomal subunits.

Chromatin

Threadlike complexes of DNA and histone proteins arranged into repeating units called nucleosomes.

Interphase

The non-dividing phase of the cell cycle comprising growth ($G_1$), DNA synthesis ($S$), and final division preparation ($G_2$).

Prophase

The first phase of mitosis in which chromatin condenses into chromosomes, nucleoli disappear, and the mitotic spindle forms.

Metaphase

The mitotic phase in which chromosomes line up individually along the equator or metaphase plate of the cell.

Anaphase

The mitotic phase in which centromeres split and sister chromatids are pulled apart to opposite poles by kinetochore motor proteins.

Telophase

The final mitotic phase in which nuclear envelopes reform around daughter chromosome sets, chromatin uncoils, and nucleoli reappear.

Cytokinesis

The division of the cytoplasm following nuclear division, mediated by an actin contractile ring that forms a cleavage furrow.

Transcription

The process occurring in the cell nucleus in which genetic information in DNA is copied into messenger RNA (mRNA).

Translation

The process occurring at ribosomes where information encoded in mRNA is used to assemble amino acids into a polypeptide chain.

Anatomy

The scientific study of the structure and organization of the human body.

Physiology

The scientific study of the functions and biological processes of the body.

Principle of Complementarity

The core anatomical concept stating that structure and function are directly intertwined and inseparable.

Gross Anatomy

The study of macroscopic body structures that can be examined without the aid of a microscope.

Microscopic Anatomy

The study of body structures requiring microscopic magnification, encompassing cytology and histology.

Inspection

A physical examination technique using the sense of sight to observe physical characteristics of an individual.

Palpation

A physical examination technique using touch to evaluate physical signs and structures beneath the skin.

Auscultation

A physical examination technique using the sense of hearing to listen to body sounds.

Percussion

A clinical examination technique where an examiner taps on the body to evaluate tissue location and density using touch and sound.

Axial Region

The main central axis of the body, consisting of the head, neck, and trunk.

Appendicular Region

The structural division of the body consisting of the upper and lower limbs.

Superior (Cranial)

Directional term meaning toward the head end or upper part of a structure or the body; above.

Inferior (Caudal)

Directional term meaning away from the head end or toward the lower part of a structure or the body; below.

Anterior (Ventral)

Directional term meaning toward or at the front of the body; in front of.

Posterior (Dorsal)

Directional term meaning toward or at the back of the body; behind.

Medial

Directional term meaning toward or at the midline of the body; on the inner side of.

Lateral

Directional term meaning away from the midline of the body; on the outer side of.

Proximal

Directional term describing a position closer to the origin of a body part or point of limb attachment to the trunk.

Distal

Directional term describing a position farther from the origin of a body part or point of limb attachment to the trunk.

Superficial (External)

Directional term meaning toward or at the surface of the body.

Deep (Internal)

Directional term meaning away from the body surface; more internal.

Ipsilateral

Anatomical term indicating structures located on the same side of the body.

Contralateral

Anatomical term indicating structures located on opposite sides of the body.

Coronal Plane (Frontal Plane)

A vertical plane that divides the body or organ into anterior (front) and posterior (back) portions.

Sagittal Plane

A vertical plane that divides the body or organ into right and left sections.

Midsagittal Plane (Median Plane)

A specific sagittal plane passing directly through the midline that divides the body into equal right and left halves.

Transverse Plane

A horizontal plane that divides the body into superior (upper) and inferior (lower) portions.

Parietal Serosa

The outer layer of a double-layered serous membrane that lines the interior walls of a body cavity.

Visceral Serosa

The inner layer of a double-layered serous membrane that directly covers the surface of internal organs.

Homeostasis

The existence and maintenance of a stable, dynamic internal environment within narrow physiological limits.

Negative Feedback System

A primary homeostatic control mechanism in which the effector response opposes or negates the initial stimulus.

Positive Feedback System

A homeostatic control mechanism in which the effector reinforces or amplifies the original change in the variable until stopped by an outside event.

Atom

The smallest unit of matter that retains its chemical properties, composed of protons, neutrons, and electrons.

Atomic Number

An element's unique identifier equal to the total number of protons contained within the atomic nucleus.

Mass Number

The total sum of protons plus neutrons contained within the nucleus of a specific atom.

Isotope

A structural variation of an element having the same atomic number but a different mass number due to varying neutron counts.

Radioisotope

An unstable isotope that decays over time, emitting high-energy radiation to attain a more stable nuclear configuration.

Solution

A homogeneous mixture of two or more components consisting of a solute dissolved uniformly in a solvent.

Octet Rule

The chemical principle stating that an atom is most stable when its outermost valence shell contains 8 electrons.

Ionic Bond

A chemical bond resulting from the complete transfer of valence electrons from a metal atom to a non-metal atom, forming attracting ions.

Electrolytes

Cations and anions formed when salts dissociate in water or bodily fluids, capable of conducting electrical currents.

Covalent Bond

A strong chemical bond formed when two or more atoms share one or more pairs of valence electrons.

Nonpolar Covalent Bond

A covalent bond in which bonding electrons are shared equally between atoms, resulting in no charge separation.

Polar Covalent Bond

A covalent bond in which electrons are shared unequally, producing partial positive ($\delta^+$) and partial negative ($\delta^-$) charges.

Hydrogen Bond

A weak electrostatic attraction between a partially positive hydrogen atom and a partially negative atom of another compound or region.

Activation Energy

The initial energy