Tour of the Eukaryotic Cell – Key Vocabulary

A comprehensive set of vocabulary flashcards summarizing structures, processes, and theories discussed in the lecture on eukaryotic cells.

Eukaryotic Cell

Cell type characterized by a nucleus, membrane-bound organelles, and a cytoskeleton.

Cell Membrane (Plasma Membrane)

Phospholipid bilayer with proteins that forms a selectively permeable barrier around the cell.

Cell Wall

Rigid outer layer found in plants, fungi, and some protists that provides strength and protection against osmotic pressure.

Cellulose

Structural polysaccharide that makes up plant cell walls.

Chitin

Polysaccharide that composes fungal cell walls.

Flagellum

Long whip-like appendage used for motility; moves in a wave-like manner in eukaryotes.

Cilium

Short hair-like projection that moves fluid or the cell itself; abundant in respiratory tract cells.

Nucleus

Command center containing DNA; enclosed by a double-layered nuclear envelope with pores.

Nucleolus

Dense region inside the nucleus where rRNA is synthesized and ribosomal subunits assemble.

Chromatin

DNA-protein complex that constitutes genetic material in its relaxed form.

Nuclear Pore

Opening in the nuclear envelope allowing controlled exchange of materials such as mRNA.

Ribosome

rRNA-protein complex that translates mRNA into polypeptides; 80S in eukaryotes, 70S in bacteria.

Rough Endoplasmic Reticulum (RER)

Membranous network studded with ribosomes; site of synthesis and initial transport of secreted proteins.

Smooth Endoplasmic Reticulum (SER)

ER lacking ribosomes; synthesizes steroids, stores calcium, and forms transport vesicles.

Golgi Apparatus

Stacked membranous sacs that process, modify, and package proteins into vesicles (cis = receiving; trans = shipping).

Vacuole

Membrane sac; small and numerous in animals, large central tonoplast in plants for storage and osmotic regulation.

Tonoplast

Membrane surrounding the large central vacuole of plant cells.

Lysosome

Specialized acidic vacuole containing hydrolytic enzymes that digest and recycle cellular material.

Peroxisome

Microbody with oxidative enzymes (e.g., catalase) that break down fatty acids and detoxify alcohol, releasing H₂O₂.

Microbody

Generic term for small enzyme-filled vesicles such as peroxisomes.

Endomembrane System

Interconnected internal membranes including ER, Golgi, lysosomes, vesicles, and plasma membrane for protein trafficking.

Endocytosis

Active uptake of external material via membrane invagination and vacuole formation.

Exocytosis

Secretion of cellular contents when a vesicle fuses with the plasma membrane.

Phagocytosis

Type of endocytosis in which the cell engulfs large particles or other cells ('cell eating').

Pinocytosis

Type of endocytosis involving ingestion of extracellular fluid ('cell drinking').

Mitochondrion

Organelle that generates ATP via aerobic respiration; has its own DNA and double membrane.

Chloroplast

Plant plastid that conducts photosynthesis, converting light energy into glucose; contains stacks of thylakoids.

Thylakoid

Flattened membranous sac inside chloroplasts that houses photosynthetic pigments like chlorophyll.

Leucoplast

Colorless plastid in plants specialized for storage, mainly of starch.

Endosymbiotic Theory

Hypothesis that mitochondria and chloroplasts originated as free-living bacteria engulfed by a nucleated ancestor.

Cytoplasm

All cellular contents between the nucleus and plasma membrane; includes cytosol and organelles.

Cytosol

Aqueous fluid portion of the cytoplasm containing water, ions, and nutrients.

Cytoskeleton

Network of protein fibers (microtubules, actin filaments, intermediate filaments) providing structure and facilitating movement.

Microtubule

Hollow tube of tubulin that aids in organelle movement, cell division, and forms cilia/flagella cores.

Actin Filament (Microfilament)

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

Intermediate Filament

Medium-sized cytoskeletal fiber providing tensile strength and mechanical support.

Centriole

Cylindrical microtubule structure in animal cells that helps organize microtubules during cell division.

Plasmodesma (plural: Plasmodesmata)

Cytoplasmic channel through plant cell walls that connects adjacent cells for communication.

Catalase

Peroxisomal enzyme that converts toxic hydrogen peroxide into water and oxygen.

70S Ribosome

Size of bacterial ribosome (and those in mitochondria/chloroplasts), supporting endosymbiotic evidence.

80S Ribosome

Larger ribosome found in eukaryotic cytoplasm composed of 60S and 40S subunits.