Eukaryotic Cell Structure and Function

Vocabulary practice flashcards covering cell organelles, endomembrane components, cytoskeletal structure, extracellular matrix, and cellular junctions based on lecture notes.

Nucleus

The eukaryotic organelle that contains most of the cell's DNA and genetic instructions.

Nuclear envelope

A double membrane perforated by pore complexes that encloses the nucleus and regulates the entry and exit of molecules.

Chromatin

The complex of DNA and histone proteins located within the nucleus that condenses to form chromosomes during cell division.

Ribosomes

Cellular complexes made of ribosomal RNA and protein that carry out protein synthesis in the cytosol or bound to the endoplasmic reticulum and nuclear envelope.

Endomembrane system

A cellular network consisting of the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, and plasma membrane, connected physically or via transfer vesicles.

Endoplasmic reticulum (ER)

An extensive membranous network continuous with the nuclear envelope, accounting for more than half of the total membrane in many eukaryotic cells.

Smooth ER

The portion of the endoplasmic reticulum that lacks ribosomes and functions in lipid synthesis and metabolic processes.

Rough ER

The portion of the endoplasmic reticulum studded with ribosomes that synthesizes membrane proteins and glycoproteins.

Glycoproteins

Proteins that have carbohydrates covalently bonded to them, synthesized and secreted by the rough ER.

Golgi apparatus

An organelle consisting of flattened membranous sacs (cisternae) that modifies, sorts, and packages ER products into transport vesicles.

Cis face

The receiving side of the Golgi apparatus located near the ER where transport vesicles fuse.

Trans face

The shipping side of the Golgi apparatus that dispatches packaged vesicles to other cell locations or the plasma membrane.

Lysosome

A membranous sac of hydrolytic enzymes that animal cells use to digest macromolecules, functioning optimally in acidic environments.

Phagocytosis

A cellular process where a cell engulfs large particles or substances, forming a food vacuole that fuses with a lysosome for digestion.

Autophagy

A recycling process in which lysosomes use hydrolytic enzymes to break down and recycle the cell's own damaged organelles.

Central vacuole

A large membranous sac in mature plant cells that plays a major role in growth, storage, and sequestering materials.

Endosymbiont theory

The evolutionary theory stating that mitochondria and chloroplasts originated as prokaryotic cells engulfed by an ancestral eukaryotic host cell.

Cristae

Infoldings of the inner membrane of a mitochondrion that present a large surface area for enzymes involved in cellular respiration.

Mitochondrial matrix

The compartment enclosed by the inner mitochondrial membrane containing enzymes, mitochondrial DNA, and ribosomes.

Chloroplasts

Photosynthetic organelles found in plants and algae that capture light energy and convert it into chemical energy.

Thylakoids

Flattened, membranous sacs inside chloroplasts stacked into grana where light absorption and energy conversion occur.

Stroma

The dense fluid surrounding the thylakoids within a chloroplast, containing chloroplast DNA, ribosomes, and enzymes.

Peroxisomes

Specialized metabolic compartments that contain enzymes that transfer hydrogen atoms to oxygen, producing hydrogen peroxide ($H_2O_2$) before converting it to water.

Cytoskeleton

A network of microtubule, microfilament, and intermediate filament fibers extending throughout the cytoplasm that provides structural support and interacts with motor proteins for cell motility.

Microtubules

Thick, hollow rods constructed from tubulin proteins that shape the cell, guide organelle transport, and control the beating of flagella and cilia.

Centrosome

A region near the nucleus in animal cells that functions as a microtubule-organizing center and contains a pair of centrioles.

Centrioles

A pair of structures in the centrosome of animal cells, each composed of nine sets of triplet microtubules arranged in a ring.

Dyneins

Large ATP-powered motor proteins attached to microtubule doublets in cilia and flagella that drive bending movements.

Basal body

A eukaryotic cell structure consisting of a $9+0$ pattern of microtubule triplets that anchors a cilium or flagellum to the cell.

Microfilaments

Thin, solid rods composed of actin protein molecules arranged as a twisted double chain that function in maintaining cell shape, muscle contraction, and cell motility.

Cortex

The outer gel-like region of cytoplasm directly beneath the plasma membrane, formed by a dense network of microfilaments.

Myosin

A motor protein that interacts with actin microfilaments to cause muscle cell contraction, amoeboid movement, and cytoplasmic streaming.

Pseudopodia

Cellular extensions formed by microfilament assembly that allow cells to crawl across surfaces during amoeboid movement.

Cytoplasmic streaming

A circular flow of cytoplasm within plant cells mediated by actin-myosin interactions that speeds up the movement of organelles and solutes.

Intermediate filaments

Fibrous cytoskeletal proteins supercoiled into cables that are intermediate in size, providing permanent structural support to maintain cell shape and fix organelle positions.

Cell wall

An extracellular layer made of cellulose fibers embedded in polysaccharides and proteins that protects plant cells, maintains their shape, and prevents excessive water uptake.

Extracellular Matrix (ECM)

An elaborate meshwork of glycoproteins, proteoglycans, and polysaccharides secreted by animal cells that regulates cell behavior, gene activity, and mechanical signaling.

Integrins

Transmembrane receptor proteins that link the extracellular matrix on the outside of animal cells to microfilaments of the cytoskeleton on the inside.

Plasmodesmata

Open channels passing through adjacent plant cell walls that connect cytoplasm and allow water, small solutes, proteins, and RNA to pass between cells.

Tight junctions

Cellular junctions in animal epithelial tissues where neighbor cell membranes are tightly bound to prevent the passage of extracellular fluid across a layer of cells.

Desmosomes

Anchoring junctions in animal tissues that fasten cells together into strong sheets, anchored into the cytoplasm by intermediate filaments.

Gap junctions

Communicating junctions in animal cells consisting of membrane proteins surrounding a pore that allows ions, sugars, and small molecules to pass directly between adjacent cells.