Cell Structure and Function – Key Vocabulary

Vocabulary flashcards covering major structures, functions, and theories related to prokaryotic and eukaryotic cell organization, suitable for exam review.

Cell Theory

Principle stating that all organisms are made of cells, cells are the basic units of structure and function, and all cells arise from pre-existing cells.

Prokaryotic Cell

Simple, unicellular cell type lacking a membrane-bound nucleus and organelles; domains Bacteria and Archaea.

Eukaryotic Cell

Cell type possessing a membrane-bound nucleus, compartmentalized organelles, and cytoskeleton; includes plant and animal cells.

Plasma Membrane

Phospholipid bilayer with embedded proteins that encloses cell contents and regulates material passage.

Cell Wall

Rigid outer layer that maintains cell shape; contains peptidoglycan in bacteria and cellulose in plants.

Glycocalyx

Polysaccharide layer outside the prokaryotic cell wall; may form a capsule for protection and adhesion.

Cytoplasm

Semifluid matrix inside the plasma membrane containing water, solutes, enzymes, and organelles.

Nucleoid

Region in prokaryotes where the single circular DNA molecule is located.

Plasmid

Small, extrachromosomal ring of DNA in prokaryotes providing accessory genes such as antibiotic resistance.

Ribosome

rRNA-protein complex that synthesizes polypeptides; free in cytosol or bound to rough ER.

Flagella (Prokaryotic)

Long, rotating helical filaments that propel prokaryotic cells.

Fimbriae

Short, bristle-like surface fibers on bacteria used for attachment.

Conjugation Pilus

Rigid tubular structure that transfers DNA between bacterial cells during conjugation.

Mesosome

Plasma-membrane invagination in bacteria, thought to increase surface area for cellular processes.

Peptidoglycan

Complex polymer of sugars and amino acids forming the bacterial cell wall.

Endosymbiotic Theory

Hypothesis that mitochondria and chloroplasts originated from free-living prokaryotes engulfed by an ancestral eukaryote.

Endomembrane System

Interconnected network of nuclear envelope, ER, Golgi, vesicles, and lysosomes that synthesizes, modifies, and transports cellular products.

Nucleus

Membrane-bound control center that houses DNA and coordinates gene expression.

Nuclear Envelope

Double membrane surrounding the nucleus, continuous with ER.

Nuclear Pore

Protein-lined channel in nuclear envelope permitting selective exchange between nucleoplasm and cytoplasm.

Chromatin

DNA-protein complex in the nucleus; condenses into chromosomes during cell division.

Chromosome

Rod-shaped structure of condensed chromatin carrying genetic information.

Nucleolus

Dense nuclear region where rRNA is transcribed and ribosome subunits are assembled.

Endoplasmic Reticulum (ER)

Extensive membranous network; divided into rough ER (protein synthesis) and smooth ER (lipid synthesis, detoxification).

Rough ER

ER region studded with ribosomes; produces proteins and glycoproteins for membranes or secretion.

Smooth ER

ER lacking ribosomes; synthesizes lipids, breaks down toxins, stores Ca²⁺.

Golgi Apparatus

Stack of cisternae that modifies, sorts, and packages proteins and lipids into vesicles.

Transport Vesicle

Small membrane sac that shuttles molecules between components of the endomembrane system.

Secretory Vesicle

Vesicle delivering substances to the plasma membrane for exocytosis.

Lysosome

Animal-cell vesicle containing acidic hydrolase enzymes that digest macromolecules and worn-out organelles.

Vacuole

Membrane-bound sac for storage; central vacuole in plants maintains turgor pressure and stores metabolites.

Peroxisome

Microbody containing enzymes that transfer hydrogen to oxygen, break down fatty acids, and detoxify compounds.

Microbody

General term for small, enzyme-filled organelles such as peroxisomes.

Mitochondrion

Double-membraned organelle with cristae that performs cellular respiration and produces ATP.

Cristae

Infoldings of the inner mitochondrial membrane increasing surface area for ATP production.

Chloroplast

Photosynthetic plastid in plants; converts light energy to chemical energy as carbohydrates.

Thylakoid

Flattened membrane sac inside chloroplasts; contains chlorophyll and other pigments.

Grana

Stacks of thylakoids within a chloroplast.

Stroma

Fluid interior of chloroplast surrounding thylakoids; site of Calvin cycle.

Cytoskeleton

Dynamic network of protein filaments (microfilaments, intermediate filaments, microtubules) providing structure and transport.

Microfilament (Actin Filament)

Thin actin protein fiber involved in cell shape, motility, and muscle contraction.

Intermediate Filament

Stable keratin-like fiber providing tensile strength and structural support.

Microtubule

Hollow tubulin cylinder guiding organelle movement, cell division, and forming cilia and flagella.

Centrosome

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

Centriole

Short microtubule triplet structure aiding spindle formation during cell division.

Cilia

Short, numerous 9+2 microtubule projections that move fluid or propel cells.

Flagellum (Eukaryotic)

Long 9+2 microtubule appendage driving cell locomotion (e.g., sperm).

Polyribosome

Cluster of ribosomes translating a single mRNA simultaneously.

Central Vacuole

Large plant vacuole occupying up to 90% of cell volume; stores materials and maintains pressure.