Cell Theory, History, and Cell Structure

Vocabulary flashcards covering historical contributors to cell theory and the structure, components, and functions of prokaryotic and eukaryotic cells.

Cell

Smallest structural and functional unit of life capable of independent activity.

Cell Theory

Set of postulates stating that all living things are composed of cells, cells are the basic unit of life, arise from pre-existing cells, contain DNA, share basic chemistry, and have internal energy flow.

Zacharias Jansen

Dutch eyeglass maker credited with building an early compound microscope (1597).

Anton van Leeuwenhoek

Dutch merchant who improved microscopes and first observed bacteria (“animalcules”) in 1665.

Robert Hooke

English polymath who coined the term “cell” after viewing cork tissue in 1666.

René Joachim Henri Dutrochet

French physiologist who emphasized cells’ role in organism function and studied osmosis (1824).

Matthias Schleiden

Botanist who concluded all plants are made of cells (1838).

Theodor Schwann

Physiologist who concluded all animals are made of cells (1839); proposed cells arise from pre-existing cells.

Rudolf Virchow

Pathologist who popularized “Omnis cellula e cellula,” confirming cells arise only from pre-existing cells (1855).

Organelle

Membrane-bound or non-membranous structure within a cell that performs a specific function.

Cytoplasm

Jellylike region inside the plasma membrane containing cytosol and organelles (excluding nucleus).

Cytosol

Semi-fluid component of cytoplasm composed mainly of water, proteins, and solutes.

Nucleus

Double-membrane organelle that houses DNA, forms chromatin, and controls cellular activities.

Nuclear Envelope

Double membrane surrounding the nucleus, continuous with rough ER, perforated by pores.

Nuclear Pores

Openings in the nuclear envelope that regulate molecular traffic between nucleus and cytoplasm.

Nuclear Lamina

Protein meshwork lining the inner nuclear membrane, maintaining nuclear shape.

Chromatin

DNA-protein complex in non-dividing cells; condenses into chromosomes during cell division.

Nucleolus

Dense nuclear region where rRNA synthesis and initial ribosome assembly occur.

Ribosome

rRNA-protein particle consisting of large and small subunits that synthesizes polypeptides.

Free Ribosome

Ribosome suspended in cytosol; produces proteins that function within the cytoplasm.

Bound Ribosome

Ribosome attached to rough ER or nuclear envelope; makes proteins destined for membranes or secretion.

Endomembrane System

Interconnected membranes: nuclear envelope, ER, Golgi, lysosomes, vacuoles, and plasma membrane.

Endoplasmic Reticulum (ER)

Extensive membranous network of cisternae; continuous with nuclear envelope.

Smooth ER

ER lacking ribosomes; synthesizes lipids, detoxifies drugs, and stores Ca²⁺.

Rough ER

ER studded with ribosomes; folds secretory proteins and produces membrane.

Cisternae

Flattened sacs or tubules composing ER and Golgi membranes.

ER Lumen

Internal cavity of the ER where newly synthesized proteins fold.

Transitional ER

Region of ER where transport vesicles bud off toward the Golgi apparatus.

Golgi Apparatus

Stack of membranous cisternae that modifies, sorts, and ships ER products.

Cis Face

Receiving side of the Golgi apparatus facing the ER.

Trans Face

Shipping side of the Golgi apparatus that buds off vesicles to other destinations.

Lysosome

Acidic, enzyme-filled vesicle that digests macromolecules and recycles cellular components.

Autophagy

Lysosomal process that recycles the cell’s own organelles and macromolecules.

Phagocytosis

Cellular ingestion of large particles or cells, forming a food vacuole that fuses with lysosomes.

Vacuole

Large vesicle derived from ER and Golgi; functions in storage, transport, or maintenance.

Central Vacuole

Large plant vacuole storing ions, water, and metabolites; key to cell growth and turgor.

Mitochondrion

Double-membrane organelle where cellular respiration and ATP production occur.

Cristae

Folded inner mitochondrial membrane that increases surface area for respiration enzymes.

Mitochondrial Matrix

Inner compartment containing enzymes, mitochondrial DNA, and ribosomes.

Chloroplast

Plant plastid containing chlorophyll; site of photosynthesis.

Thylakoid

Flattened sac inside chloroplast where light reactions occur.

Granum

Stack of thylakoids within a chloroplast.

Stroma

Fluid outside thylakoids containing chloroplast DNA, ribosomes, and Calvin-cycle enzymes.

Plastid

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

Amyloplast

Colorless plastid that stores starch, especially in roots and tubers.

Chromoplast

Plastid containing pigments that give fruits and flowers their colors.

Peroxisome

Single-membrane organelle that uses oxidation reactions to break down molecules, producing and degrading H₂O₂.

Cytoskeleton

Network of protein fibers (microtubules, microfilaments, intermediate filaments) providing support, transport, and motility.

Microtubule

Hollow tubulin fiber; thickest cytoskeletal element; forms tracks, cilia, flagella, and mitotic spindle.

Microfilament (Actin Filament)

Thin actin strand involved in cell shape, muscle contraction, and cytoplasmic streaming.

Intermediate Filament

Fibrous protein cable providing tensile strength and maintaining organelle position.

Centrosome

Microtubule-organizing center near nucleus; contains a pair of centrioles in animal cells.

Centriole

Cylindrical structure of nine microtubule triplets found in animal centrosomes.

Cilium

Short, numerous microtubule-based appendage that moves fluid or cell with rhythmic beating.

Flagellum

Long, usually singular appendage that propels a cell with whip-like motion.

Extracellular Matrix (ECM)

Network of glycoproteins (collagen, proteoglycans, fibronectin) surrounding animal cells, providing support and signaling.

Integrin

Transmembrane receptor linking ECM proteins to the cytoskeleton.

Cell Wall

Rigid extracellular layer in plants, fungi, and some protists; composed mainly of cellulose in plants.

Plasmodesmata

Channels through plant cell walls allowing cytoplasmic exchange between adjacent cells.

Tight Junction

Animal cell junction where membranes are pressed together, preventing fluid leakage.

Desmosome

Anchoring junction fastening animal cells into strong sheets via intermediate filaments.

Gap Junction

Communicating junction in animals providing cytoplasmic channels between neighboring cells.