Marieb Human Anatomy & Physiology - Chapter 3: Cells: The Living Units

Vocabulary practice flashcards covering cell structure, membrane transport, cytoplasmic organelles, cytoskeleton, and nuclear architecture based on Marieb Human Anatomy & Physiology, Chapter 3.

Cell Theory

The scientific principle stating that the cell is the structural and functional unit of life, all organisms are composed of one or more cells, and cells arise only from pre-existing cells.

Interstitial Fluid

Extracellular fluid in which body tissue cells are bathed or submersed.

Fluid Mosaic Model

A structural model depicting the plasma membrane as an active, moving bilayer of phospholipids with embedded proteins, smaller amounts of cholesterol, and surface glycocalyx sugars.

Phospholipid

The primary lipid of the plasma membrane, possessing a charged, polar hydrophilic (water-loving) phosphate head and two uncharged, nonpolar hydrophobic (water-hating) fatty acid tails.

Integral Proteins

Membrane proteins inserted into the lipid bilayer (most being transmembrane) having hydrophobic and hydrophilic regions; they function as transport channels, carriers, enzymes, or receptors.

Peripheral Proteins

Proteins loosely attached to integral proteins or membrane surfaces that function as enzymes, motor proteins for cell shape changes, or cell-to-cell connections.

Diffusion

The passive movement of molecules down their concentration gradient from an area of high concentration to an area of low concentration, driven by intrinsic thermal kinetic energy.

Simple Diffusion

Passive transport in which nonpolar, lipid-soluble (hydrophobic) substances such as oxygen, carbon dioxide, steroid hormones, and fatty acids diffuse directly across the phospholipid bilayer unassisted.

Carrier-Mediated Facilitated Diffusion

Passive transport in which specific large or polar molecules (such as glucose and amino acids) bind to transmembrane carrier proteins, inducing a conformational change that moves the solute across.

Channel-Mediated Facilitated Diffusion

Passive transport of solutes (mostly ions) through transmembrane proteins with aqueous-filled cores, categorized as always-open leakage channels or controlled gated channels.

Aquaporins (AQPs)

Transmembrane channel proteins dedicated to the passage of water molecules across the plasma membrane during osmosis.

Osmolarity

The total concentration of all solute particles in a solution, expressed in units of osmoles per liter ($\text{osmol/L}$).

Hydrostatic Pressure

The back pressure exerted by water against a membrane or cell wall.

Osmotic Pressure

The tendency of water to move into a cell or compartment by osmosis.

Tonicity

The ability of an extracellular solution to alter a cell's internal water volume and membrane tension, categorizing solutions as isotonic, hypertonic, or hypotonic.

Crenation

The shrinking of a cell that occurs when it is placed in a hypertonic solution due to the osmotic loss of water.

Lysing

The swelling and bursting of a cell that occurs when it is placed in a hypotonic solution due to excessive osmotic water influx.

Primary Active Transport

Solute transport against a concentration gradient directly powered by the hydrolysis of ATP, which phosphorylates and alters the shape of transport pumps.

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

A primary active transport enzyme ($Na^+-K^+$ ATPase) that pumps three $Na^+$ ions out of the cell and two $K^+$ ions into the cell per molecule of ATP hydrolyzed.

Secondary Active Transport

A cotransport process driven indirectly by ionic concentration gradients established by primary active transport pumps, moving a solute against its gradient as an ion (such as $Na^+$) flows down its gradient.

Symporter

A membrane cotransporter protein that moves two different substances simultaneously in the same direction across the plasma membrane.

Antiporter

A membrane transport protein that moves one substance into the cell while transporting a different substance out of the cell.

Phagocytosis

A type of endocytosis ('cell eating') in which a cell extends pseudopods to engulf large solid particles, enclosing them within a membranous sac termed a phagosome.

Pinocytosis

A nonspecific form of endocytosis ('cell drinking') where the cell membrane infolds to engulf extracellular fluid and dissolved solutes into tiny vesicles.

Receptor-Mediated Endocytosis

A selective vesicular uptake mechanism in which specific extracellular ligands bind to membrane receptors, triggering internalization in protein-coated vesicles.

v-SNARE and t-SNARE

Vesicle surface proteins (v-SNAREs) and target plasma membrane proteins (t-SNAREs) that bind and interlock to form a fusion pore, triggering exocytosis.

Resting Membrane Potential (RMP)

The steady electrical voltage across a resting cell's plasma membrane, typically ranging from $-50\,\text{mV}$ to $-100\,\text{mV}$, produced by the separation of oppositely charged ions and maintained primarily by $K^+$ leakage.

Mitochondria

Double-membraned 'power plant' organelles containing inner cristae, matrix, their own DNA, RNA, and ribosomes, responsible for producing the majority of cellular ATP via aerobic cellular respiration.

Ribosomes

Nonmembranous cytoplasmic granules made of protein and ribosomal RNA (rRNA) that serve as sites of protein synthesis, existing either as free ribosomes or membrane-bound ribosomes.

Rough Endoplasmic Reticulum

A membranous organelle continuous with the outer nuclear membrane and studded externally with ribosomes, serving in the synthesis and cistern modification of secreted proteins, membrane proteins, and phospholipids.

Smooth Endoplasmic Reticulum

A continuous network of tubule membranes lacking ribosomes that functions in lipid metabolism, steroid hormone synthesis, chemical detoxification, glycogen-to-glucose conversion, and calcium storage.

Golgi Apparatus

A series of stacked membranous cisterns featuring a receiving cis face and a shipping trans face that modifies, concentrates, and packages proteins and lipids into vesicles.

Lysosomes

Spherical membranous organelles containing acid hydrolases that safely digest ingested pathogens, worn-out organelles, and metabolic stores, or trigger autolysis upon injury.

Tay-Sachs Disease

A fatal genetic neurodegenerative disease in which lysosomes lack the specific enzyme required to break down membrane glycolipids in nerve cells, causing organelle swelling and a characteristic cherry red spot on the retina.

Peroxisomes

Membranous sacs housing detoxifying oxidases (which form toxic $H_2O_2$) and catalases (which convert $H_2O_2$ into harmless water) to neutralize toxic free radicals and metabolize fatty acids.

Endomembrane System

An interactive cellular network comprising the nuclear envelope, rough and smooth ER, Golgi apparatus, lysosomes, secretory vesicles, and plasma membrane that manufactures, modifies, stores, and transports molecules.

Microfilaments

The thinnest cytoskeletal elements ($7\,\text{nm}$ diameter), composed of semi-flexible actin strands that form the terminal web to strengthen the cell surface and enable cell motility and shape changes.

Intermediate Filaments

Tough, ropelike cytoskeletal protein fibers ($10\,\text{nm}$ diameter) formed of tetramer fibrils that resist mechanical pulling forces and anchor to desmosome plaques.

Microtubules

Hollow, dynamic cytoskeletal cylinders ($25\,\text{nm}$ diameter) composed of tubulin protein subunits radiating from the centrosome that maintain cell shape and provide tracks for ATP-powered motor proteins.

Centrioles

A pair of barrel-shaped organelles inside the centrosome, each constructed of nine triplets of microtubules arranged in a pinwheel array, which organize the mitotic spindle and form basal bodies.

Basal Body

A centriole-derived organelle composed of a ring of nine microtubule triplets that anchors the base of a cilium or flagellum.

Cilia

Whiplike, motile cellular extensions featuring a '$9 + 2$' microtubule pattern whose coordinated power and recovery strokes propel substances across epithelial cell surfaces.

Microvilli

Minute, nonmotile fingerlike projections of the plasma membrane supported by an actin microfilament core that maximize surface area for absorption in epithelial cells.

Nuclear Lamina

A protein meshwork of intermediate filaments (lamins) lining the inner surface of the nuclear envelope that maintains nuclear shape and acts as a DNA scaffold.

Nuclear Pore Complex

An assembly of proteins ringing each nuclear pore that regulates bidirectional transport of large macromolecules into and out of the nucleus.

Nucleolus

A dark-staining spherical body within the nucleus responsible for ribosomal RNA (rRNA) synthesis and ribosome subunit assembly.

Nucleosome

The fundamental structural unit of chromatin ($10\,\text{nm}$ diameter), consisting of an octamer of eight histone proteins encircled by two winds of the DNA double helix.

Chromatin

The granular genetic material in the nucleus composed of approximately 30% DNA, 60% globular histone proteins, and 10% newly forming RNA chains.