NURS 122: Cells - The Living Unit Vocabulary Flashcards

Vocabulary flashcards covering cell theory, cellular structures, membrane components, transport processes, cytoplasmic organelles, and the cell life cycle based on lecture notes.

Cytology

The scientific study of cells.

Cell Theory

The fundamental biological principle proposed by Mathias Schleiden (1838) and Theodor Schwann (1839), expanding on Robert Hooke's 1665 discovery, which states that cells are the basic structural and functional units of living organisms, all living things are made of cells, and all cells arise from preexisting cells (Rudolf Virchow, 1850).

Cell

The smallest structural and functional unit capable of performing all life functions.

Tissues

Groups of cells that are similar in structure and function.

Prokaryotic Cells

The first cell type on earth (characteristic of Bacteria and Archaea) that lacks a membrane-bound nucleus or membrane-bound organelles and contains a nucleoid.

Eukaryotic Cells

Complex cells found in protists, fungi, plants, and animals that contain a membrane-bound nucleus and numerous membrane-bound organelles.

Nucleoid

The region of concentrated DNA in a prokaryotic cell that is not enclosed by a membrane.

Plasma Membrane

A selectively permeable double phospholipid layer that serves as an outer barrier for cell contents and determines which substances enter or leave the cell.

Fluid Mosaic Model

A model describing the plasma membrane as a dynamic fluid bilayer of phospholipids containing a mosaic mix of proteins, cholesterol, and carbohydrates.

Glycocalyx

A sticky coat on the outer surface of the cell membrane formed by carbohydrates combined with lipids and proteins, functioning in cell recognition.

Integral Proteins

Membrane proteins firmly embedded in or passing through the lipid bilayer, functioning as channels, transporters, receptors, enzymes, intracellular junctions, cytoskeleton anchors, or cell identity markers.

Peripheral Proteins

Membrane proteins located loosely on either the extracellular or intracellular surface of the lipid bilayer.

Phospholipids

The primary lipid component ($75\%$) of the plasma membrane, featuring polar hydrophilic phosphate heads pointing toward fluid and nonpolar hydrophobic fatty acid tails making up the middle of the membrane.

Glycolipids

Membrane lipids that make up $5\%$ of plasma membrane lipids and contribute to the glycocalyx.

Cholesterol

A plasma membrane lipid ($20\%$) that stabilizes the membrane and increases the mobility (fluidity) of phospholipids.

Tight Junctions

Impermeable membrane junctions that encircle adjacent cells to prevent molecules from passing between them.

Desmosomes

Anchoring membrane junctions between cells that prevent them from pulling apart under mechanical stress.

Gap Junctions

Communicating membrane junctions containing connexons that allow ions and small substances to pass directly from one cell to another.

Simple Diffusion

The passive, unassisted movement of lipid-soluble or small particles down a concentration gradient from high to low concentration until equilibrium is reached.

Osmosis

The passive diffusion of water molecules across a selectively permeable membrane from an area of higher water concentration to lower water concentration.

Osmolarity

The total concentration of all solute particles in a solution.

Osmotic Pressure

The net pressure effect ($\sigma$) created by individual particles in solution that drives water movement.

Hydrostatic Pressure

The fluid pressure ($h$) created within a solution as a result of osmosis.

Tonicity

The ability of an extracellular solution to alter the shape or tone of cells by changing their internal water volume.

Isotonic Solution

A solution with the same solute concentration inside and outside cells, resulting in no net diffusion of water.

Hypertonic Solution

A solution with a higher solute concentration than inside cells, causing water to move out of the cell so that it shrinks (crenation).

Hypotonic Solution

A solution with a lower solute concentration than inside cells, causing water to enter the cell so that it swells and may burst (lyse).

Facilitated Diffusion

A passive transport process that moves larger or charged substances across a membrane down their concentration gradient using channel or carrier proteins.

Primary Active Transport

An active transport mechanism in which membrane pumps hydrolyze ATP directly to transport substances across a membrane against their concentration gradient.

Na+/K+ ATPase

A primary active transport pump that uses energy from one ATP hydrolysis to pump $3\,\text{Na}^+$ ions out of the cell and $2\,\text{K}^+$ ions into the cell per cycle.

Secondary Active Transport

A transport process where a primary transporter uses ATP to establish an ion gradient, which then drives a carrier protein to transport a second substance by facilitated transport.

Symport

A secondary active transporter (co-transporter) that moves two substances across the membrane in the same direction.

Antiport

A secondary active transporter (counter-transporter) that moves two substances across the membrane in opposite directions.

Resting Membrane Potential

An electrical charge differential across the plasma membrane where the cell interior is negatively charged relative to the positively charged exterior.

Vesicular Transport

An active transport mechanism that moves large molecules and fluids across cell membranes inside membranous sacs called vesicles.

Endocytosis

A vesicular transport process by which particles enter cells through invagination of the plasma membrane.

Phagocytosis

A form of endocytosis known as 'cell eating,' where a cell engulfs large solid particles or bacteria using pseudopods.

Pinocytosis

A form of endocytosis known as 'cell drinking,' where a cell ingests droplets of extracellular fluid containing dissolved solutes.

Clathrin

A specialized protein that causes bending of the cell membrane to form coated pits and vesicles during endocytosis.

Exocytosis

A vesicular transport mechanism that ejects substances out of the cell when an intracellular secretory vesicle fuses with the plasma membrane.

Cytoplasm

All cellular material located between the plasma membrane and the nucleus, consisting of cytosol, organelles, and inclusions.

Cytosol

The viscous, jelly-like fluid component of cytoplasm in which organelles and soluble elements are suspended.

Inclusions

Chemical substances stored in the cytoplasm, such as glycogen granules, pigment granules, lipid droplets, vacuoles, and crystals.

Mitochondria

Double-membraned organelles ('powerhouse of the cell') containing mitochondrial DNA that generate most of the cell's ATP.

Ribosomes

Nonmembranous organelles constructed of proteins and ribosomal RNA that serve as the site of protein synthesis.

Endoplasmic Reticulum

An extensive network of interconnected fluid-filled tubules and parallel membranes enclosing cisternae within the cytoplasm.

Rough Endoplasmic Reticulum

The ribosome-studded portion of the endoplasmic reticulum that manufactures secreted proteins, integral membrane proteins, and phospholipids.

Smooth Endoplasmic Reticulum

The ribosome-free branching network of tubules in the ER that catalyzes lipid metabolism, steroid synthesis, fat absorption, drug detoxification, and $\text{Ca}^{2+}$ storage.

Golgi Apparatus

An organelle consisting of a stack of 3 to 10 disk-shaped envelopes ('protein traffic director') that modifies, packages, sorts, and ships products from the rough ER.

Lysosomes

Spherical membranous vesicles containing digestive enzymes operating in acidic conditions ($\text{pH } 5$) to break down bacteria, nonfunctional organelles, and bone tissue.

Peroxisomes

Membrane-walled sacs of redox/oxidase enzymes that detoxify harmful substances (alcohol, formaldehyde), neutralize free radicals, and break down fatty acid chains.

Cytoskeleton

An elaborate network of protein rods (microtubules, microfilaments, intermediate filaments) that provides structural framework, maintains cell shape, and aids in organelle movement.

Microtubules

Hollow, cylindrical cytoskeleton elements of large diameter made of tubulin proteins that extend from the centrosome to anchor and transport organelles.

Microfilaments

The smallest cytoskeleton filaments, composed of contractile actin protein, involved in cell motility, shape changes, and muscle contraction.

Intermediate Filaments

Tough, medium-sized protein fibers in the cytoskeleton that act as guy wires to resist mechanical pulling forces on the cell.

Cilia

Whiplike, motile extensions on cell surfaces containing microtubules that move materials across the outer cell surface.

Flagellum

A long, motile cellular extension (such as the tail on sperm) that propels the entire cell through fluid.

Microvilli

Fingerlike extensions of the plasma membrane stiffened by an actin core that increase surface area for cellular absorption.

Nucleus

The large central double-membrane organelle (approximately $5\,\mu\text{m}$ in diameter) containing DNA that acts as the control center of the cell.

Nucleolus

A dense, non-membrane-bound body inside the nucleus composed of DNA, RNA, and protein that synthesizes ribosomal RNA and assembles ribosome subunits.

Chromatin

Grainy, threadlike nuclear material consisting of DNA wrapped around histone proteins ('beads on a string') present when the cell is not dividing.

Centrosome

A spherical region near the nucleus that acts as the microtubule organizing center and contains paired centrioles.

Centrioles

Paired cylindrical bodies composed of 27 short microtubules (triplets) involved in organizing the mitotic spindle during cell division and giving rise to cilia and flagella.

Interphase

The non-dividing phase of the cell life cycle during which the cell grows, conducts metabolic functions, and replicates its DNA (composed of $\text{G}_1$, $\text{S}$, and $\text{G}_2$ phases).

G1 Phase

The first growth phase of interphase in which the cell is metabolically active, synthesizes proteins, and begins centriole replication.

S Phase

The synthetic phase of interphase during which nuclear DNA replicates itself to ensure identical genetic copies for daughter cells.

G2 Phase

The second growth phase of interphase in which centriole replication finishes and enzymes needed for cell division are synthesized.

Mitosis

The process of nuclear division during cell division (comprising prophase, metaphase, anaphase, and telophase) that distributes identical chromosomes to daughter nuclei.

Cytokinesis

The division of the cell cytoplasm that occurs after nuclear division to form two distinct daughter cells.

Prophase

The first stage of mitosis where chromatin condenses into chromosomes (held by a centromere), centrioles separate, the mitotic spindle forms, and the nuclear envelope fragments.

Metaphase

The second stage of mitosis in which chromosomes align along the equator (metaphase plate) of the cell.

Anaphase

The third and shortest stage of mitosis during which centromeres split and sister chromatids (daughter chromosomes) are pulled apart to opposite poles.

Telophase

The final stage of mitosis during which chromosomes uncoil back into chromatin, nuclear envelopes reform around daughter nuclei, and nucleoli reappear.