Cell Organelles – Vocabulary Review

25 vocabulary flashcards summarizing the structure and functions of major cell organelles and related components from the lecture notes.

Cell Membrane (Plasma Membrane / Plasmalemma)

A dynamic phospholipid-protein bilayer that encloses the cell, maintains shape, regulates selective transport, signaling, and cell-to-cell interactions.

Cell Wall

Extra, non-living layer outside the plasma membrane (cellulose in plants, chitin in fungi) that imparts rigidity, protection, filtration, and resists turgor pressure.

Centriole

Cylindrical organelle composed of nine microtubule triplets; organizes spindle fibers in cell division and gives rise to basal bodies of cilia and flagella.

Cilia

Short, numerous 9+2 microtubule projections covered by plasma membrane that create fluid movement or act as sensory structures.

Flagella

Long, whip-like appendages (flagellin helix in prokaryotes; 9+2 microtubule axoneme in eukaryotes) that propel cells through liquid.

Chloroplast

Lens-shaped, double-membrane plastid with its own DNA; contains chlorophyll in thylakoids for photosynthesis and photorespiration control.

Cytoplasm

All cellular contents between plasma membrane and nucleus; consists of cytosol, organelles, and inclusions where most metabolic reactions occur.

Cytoskeleton

Network of microtubules, microfilaments, and intermediate filaments that provides shape, mechanical support, motility, and intracellular transport.

Endoplasmic Reticulum (ER)

Continuous membranous network (rough with ribosomes for protein processing; smooth for lipid synthesis) connected to the nuclear envelope.

Endosome

Membrane-bound sorting compartment (early, late, recycling types) that directs internalized materials to Golgi, lysosomes, or back to the surface.

Golgi Apparatus (Golgi Complex)

Stack of flattened cisternae with associated vesicles and tubules that modifies, sorts, and packages proteins and lipids for transport (‘cell traffic police’).

Intermediate Filament

Mid-sized cytoskeletal fibers with coiled-coil proteins that confer tensile strength and maintain tissue integrity (e.g., in skin).

Lysosome

Spherical, single-membrane organelle packed with hydrolytic enzymes for intracellular digestion, autolysis, membrane repair, and signaling.

Microfilament (Actin Filament)

Smallest cytoskeletal fibers; helical polymers of actin that provide strength, enable cell movement, cytokinesis, and surface projections.

Microtubule

Hollow 24 nm tubes of α- and β-tubulin dimers with polarity; give shape, form spindle apparatus, and serve as tracks for organelle transport.

Microvillus (plural Microvilli)

Finger-like actin-based projections that enlarge cell surface area, enhance absorption, host digestive enzymes, and aid anchorage.

Mitochondrion

Double-membrane ‘powerhouse’ with cristae and matrix enzymes; generates ATP, regulates Ca²⁺, apoptosis, hormone synthesis, and ammonia detox (liver).

Nucleus

Large double-membrane organelle containing chromatin and nucleolus; stores genetic material, directs cellular activities, and produces rRNA.

Peroxisome

Single-membrane oxidative organelle rich in catalase and other enzymes; breaks down fatty acids, produces/removes H₂O₂, and synthesizes some lipids.

Plasmodesma (plural Plasmodesmata)

Cytoplasmic channels across plant cell walls lined by plasma membrane and ER desmotubule, permitting intercellular transport and communication.

Plastid

Double-membrane plant organelle (e.g., chloroplast, chromoplast, leucoplast) involved in photosynthesis, pigment storage, or starch storage.

Ribosome

70S (prokaryote) or 80S (eukaryote) RNA-protein complex of large and small subunits that translates mRNA into polypeptides.

Storage Granule (Zymogen Granule)

Membrane-bound inclusion that stores energy reserves, metabolites, or inactive digestive enzymes until needed.

Vacuole

Tonoplast-bound compartment containing aqueous solution of ions, nutrients, or wastes; functions in storage, pH and osmotic homeostasis, and metabolism.

Vesicle

Small lipid-bilayer sac formed during endocytosis, exocytosis, or transport; stores, moves, or digests substances within or between cells.