Prokaryotic & Eukaryotic Cells – Vocabulary Flashcards

These flashcards cover key vocabulary related to cell theory, cell types, microscopy principles, and the structure and functions of major cellular organelles in both prokaryotic and eukaryotic cells.

Cell Theory

States that all organisms are composed of one or more cells, the cell is the basic unit of life, and all cells arise from pre-existing cells.

Prokaryote

A cell type lacking a true nucleus and membrane-bound organelles; size 0.1–5 µm; includes bacteria and archaea.

Eukaryote

A cell type with a true, membrane-bound nucleus and numerous membrane-bound organelles; size 10–100 µm.

Nucleoid

Region in a prokaryotic cell where the circular DNA chromosome is located; not membrane bound.

Plasmid

Small, circular, double-stranded DNA molecule in bacteria that often carries antibiotic-resistance genes.

Capsule

Sticky outermost layer of some prokaryotes that aids adhesion and protects against desiccation and phagocytosis.

Pili

Hair-like surface appendages of prokaryotes used for attachment to surfaces and in conjugation.

Flagellum (Prokaryotic)

Long, whip-like filament used for locomotion in many bacteria.

Peptidoglycan

Complex of amino acids and polysaccharides forming the rigid bacterial cell wall.

Binary Fission

Asexual cell division method of prokaryotes in which one cell splits into two identical cells.

70S Ribosome

Smaller ribosome found in prokaryotes, mitochondria, and chloroplasts; composed of 50S + 30S subunits.

80S Ribosome

Larger ribosome typical of eukaryotic cytoplasm; composed of 60S + 40S subunits.

Nucleus

Largest organelle in eukaryotes, bounded by a double membrane and containing DNA and nucleolus.

Nuclear Envelope

Double membrane surrounding the nucleus; continuous with rough ER and perforated by nuclear pores.

Nuclear Pore

Protein-lined opening in the nuclear envelope that regulates passage of RNA and proteins.

Nucleolus

Dense, RNA-rich region inside the nucleus responsible for ribosome subunit assembly.

Chromatin

Loose, thread-like complex of DNA and histone proteins present when the cell is not dividing.

Chromosome

Condensed, visible DNA structure seen during cell division; carries genetic information.

Nucleosome

Fundamental unit of chromatin; DNA wound around a histone protein core.

Endomembrane System

Interconnected group of membranes including nuclear envelope, ER, Golgi apparatus, lysosomes, and vesicles.

Endoplasmic Reticulum (ER)

Network of membranous tubules; subdivided into rough ER (with ribosomes) and smooth ER (without).

Rough ER

ER with bound ribosomes; synthesizes, modifies, and transports proteins destined for membranes or secretion.

Smooth ER

ER lacking ribosomes; synthesizes lipids, metabolizes carbohydrates, detoxifies drugs, and stores calcium.

Golgi Apparatus

Stack of flattened membranes (cisternae) that modifies, sorts, and packages proteins and lipids for transport.

Cis Face (Golgi)

Receiving side of the Golgi apparatus that fuses with vesicles arriving from the ER.

Trans Face (Golgi)

Shipping side of the Golgi that buds off vesicles headed to the plasma membrane or lysosomes.

Lysosome

Single-membrane vesicle containing hydrolytic enzymes for intracellular digestion, autophagy, and autolysis.

Autophagy

Process by which lysosomes degrade and recycle worn-out organelles.

Autolysis

Self-destruction of a damaged cell by its own lysosomal enzymes.

Vacuole

Large membrane-bound sac used for storage and regulation of water and solutes; types include food, contractile, and central vacuoles.

Food Vacuole

Vesicle formed by phagocytosis that fuses with lysosomes to digest nutrients.

Contractile Vacuole

Organelle in freshwater protists that pumps excess water out of the cell for osmoregulation.

Central Vacuole

Prominent vacuole in mature plant cells containing cell sap; maintains turgor and stores substances.

Peroxisome

Single-membrane organelle containing catalase and other enzymes that break down fatty acids and detoxify hydrogen peroxide.

Catalase

Enzyme in peroxisomes that converts toxic hydrogen peroxide into water and oxygen.

Mitochondrion

Double-membrane organelle where aerobic respiration produces ATP; inner folds are called cristae.

ATP (Adenosine Triphosphate)

Primary energy currency produced mainly in mitochondria during cellular respiration.

Chloroplast

Plant organelle containing chlorophyll; site of photosynthesis; composed of thylakoids, grana, and stroma.

Thylakoid

Flattened membrane sac inside chloroplast where light-dependent reactions of photosynthesis occur.

Stroma

Fluid matrix surrounding thylakoids in a chloroplast; site of Calvin cycle reactions.

Plastid

Group of plant organelles that includes chloroplasts, chromoplasts, and amyloplasts.

Cytoskeleton

Network of protein filaments (microtubules, microfilaments, intermediate filaments) that supports cell shape, movement, and transport.

Microtubule

Hollow tube of tubulin protein; forms cilia, flagella, mitotic spindle, and tracks for organelle movement.

Microfilament

Thin filament of actin protein involved in cell movement, muscle contraction, and cytokinesis.

Intermediate Filament

Medium-diameter filament providing tensile strength and mechanical stability to cells.

Centrosome

Microtubule-organizing center in animal cells containing a pair of centrioles.

Centriole

Short cylinder of microtubule triplets (9 + 0) that helps organize spindle fibers during cell division.

Cilia

Short, numerous cell projections with a 9 + 2 microtubule arrangement; move fluid past cells.

Flagella (Eukaryotic)

Long, usually singular projection with 9 + 2 microtubule pattern; propels cells such as sperm.

Extracellular Matrix (ECM)

Complex network of glycoproteins (e.g., collagen, fibronectin) outside animal cells that provides support and signaling.

Collagen

Most abundant glycoprotein in animal ECM; forms strong fibers.

Integrin

Transmembrane receptor protein linking ECM fibers to the cytoskeleton.

Cell Wall

Rigid outer layer found in plants, fungi, and many prokaryotes; in plants composed mainly of cellulose.

Cellulose

Structural polysaccharide forming strong fibers in plant cell walls.

Middle Lamella

Pectin-rich layer that glues adjacent plant cell walls together.

Plasmodesmata

Cytoplasmic channels through plant cell walls allowing transport and communication between cells.

Plasma Membrane

Selective phospholipid bilayer with embedded proteins that regulates substance movement into and out of the cell.

Fluid Mosaic Model

Description of plasma membrane as a dynamic, fluid phospholipid bilayer with dispersed proteins.

Glycocalyx

Carbohydrate-rich coat on cell surface composed of glycoproteins and glycolipids that protects, stabilizes, and aids cell recognition.

Magnification

Ratio of an object’s image size to its real size in microscopy.

Resolving Power

Ability of a microscope to distinguish two closely spaced points as separate; depends on wavelength.

Resolution

Minimum distance between two points that can still be distinguished; higher resolution equals more image detail.

Light (Compound) Microscope

Instrument that uses visible light and glass lenses to magnify specimens up to about 1000×.

Dissecting (Stereo) Microscope

Low-magnification light microscope providing a 3-D view of large specimens for dissection.

Electron Microscope (EM)

Microscope that uses a beam of electrons, achieving resolution down to ~2 nm.

Transmission Electron Microscope (TEM)

EM that passes electrons through ultra-thin specimens to reveal internal structures in 2-D.

Scanning Electron Microscope (SEM)

EM that scans a metal-coated specimen with electrons to produce detailed 3-D surface images.

Svedberg Unit (S)

Unit of sedimentation rate during centrifugation; indicates size and density of ribosomal subunits.

Unicellular Organism

Living organism composed of a single cell performing all life functions.

Multicellular Organism

Organism composed of many specialized cells that work together to sustain life.