A Tour of the Cell - Biol 1111 Chapter 4

Vocabulary practice flashcards covering cell theory, prokaryotic and eukaryotic structures, organelle functions, the endomembrane system, energy organelles, cytoskeletal filaments, and cell junctions from Chapter 4 of Biol 1111.

Cell theory

The foundational biological principle stating that all living organisms are composed of one or more cells (the fundamental units of life), all cells arise from previously existing cells, and the structure of a cell is correlated to its cellular function.

Surface area-to-volume ratio

A mathematical relationship that sets the upper limit on cell size; as a cell expands, its volume increases faster than its surface area, limiting the cell's capacity to exchange sufficient nutrients and eliminate wastes across its membrane.

Plasma membrane

A selectively permeable boundary composed of a phospholipid bilayer with embedded proteins that separates the cell's internal cytoplasm from the external environment.

Cytoplasm

The interior region of a cell enclosed by the plasma membrane; its semifluid aqueous component is called the cytosol.

Prokaryotic cell

A small ($0.1 - 10\,\mu\text{m}$), structurally simple cell that lacks a nucleus and membrane-bound organelles, possesses circular DNA, and belongs to Domain Bacteria or Domain Archaea.

Eukaryotic cell

A larger ($10 - 100\,\mu\text{m}$), highly compartmentalized cell containing a membrane-bound nucleus, linear chromosomes, and specialized membrane-bound organelles, belonging to Domain Eukarya.

Nucleoid

The non-membrane-enclosed region within a prokaryotic cell where the circular bacterial chromosome is concentrated.

Fimbriae

Hair-like surface appendages on the exterior of some prokaryotic cells used for attachment to surfaces or other cells.

Nucleus

The largest eukaryotic organelle that houses genetic material in the form of DNA, bounded by a perforated double-membrane nuclear envelope.

Nuclear envelope

A double membrane enclosing the eukaryotic nucleus, perforated by protein-lined pores that regulate the transport of macromolecules between the nucleus and the cytoplasm.

Nucleolus

A prominent, dense structure inside the nucleus where ribosomal RNA is synthesized and assembled into ribosomal subunits.

Chromatin

The complex of DNA double helices and histone proteins residing in the eukaryotic nucleus that condenses into distinct chromosomes during cell division.

Ribosomes

Non-membranous cellular particles made of ribosomal RNA and protein complexes that carry out protein synthesis, occurring either freely suspended in cytosol or bound to the endoplasmic reticulum.

Endomembrane system

A collective network of internal membranes in eukaryotic cells—comprising the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, and plasma membrane—that synthesizes, modifies, stores, and transports cellular products.

Smooth endoplasmic reticulum

The portion of the endoplasmic reticulum lacking surface ribosomes; functions include the synthesis of lipids, storage of calcium ions, and detoxification of drugs and poisons.

Rough endoplasmic reticulum

The portion of the endoplasmic reticulum studded with ribosomes on its outer surface; synthesizes cellular proteins and glycoproteins, ensures correct folding, and packages products into transport vesicles.

Golgi apparatus

An organelle consisting of flattened membranous sacs that receives vesicles at its cis face, chemically modifies and sorts proteins, and ships them from its trans face.

Lysosome

A membranous sac maintaining an acidic internal environment ($\text{pH } 4 - 5$) packed with hydrolytic digestive enzymes that break down engulfed macromolecules and worn-out cellular organelles.

Phagocytosis

A cellular digestion mechanism where a cell engulfs external particles or bacteria into a food vacuole that subsequently fuses with a lysosome.

Autophagy

A lysosomal process in which a lysosome fuses with a vesicle surrounding old or damaged organelles to break them down for organic recycling.

Contractile vacuole

A specialized organelle found in freshwater protists that accumulates and periodically expels excess incoming water to maintain osmotic balance.

Central vacuole

A prominent compartment in plant cells that absorbs water to maintain turgor pressure and serves to store vital nutrients, chemicals, and defensive toxins.

Mitochondria

Double-membrane organelles that carry out cellular respiration ($\text{C}_6\text{H}_{12}\text{O}_6 + \text{O}_2 \rightarrow \text{CO}_2 + \text{H}_2\text{O} + \text{ATP}$), harvesting chemical energy from food molecules to generate ATP.

Cristae

The extensive folds of the inner mitochondrial membrane that greatly increase surface area for the embedded proteins involved in ATP synthesis.

Mitochondrial matrix

The fluid-filled compartment bounded by the inner mitochondrial membrane that contains mitochondrial DNA, ribosomes, and catalytic respiratory enzymes.

Chloroplasts

Double-membrane photosynthetic organelles found in plants and algae that convert solar light energy into chemical energy stored in glucose ($\text{Light} + \text{CO}_2 + \text{H}_2\text{O} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + \text{O}_2$).

Thylakoids

Interconnected membranous flattened sacs located within chloroplasts, stacked into grana, which contain chlorophyll molecules and serve as the reaction sites for photosynthesis.

Stroma

The dense fluid space contained within the inner chloroplast membrane surrounding the thylakoid grana, housing chloroplast DNA, ribosomes, and metabolic enzymes.

Endosymbiont theory

The evolutionary theory stating that mitochondria and chloroplasts originated as small prokaryotes that were engulfed by ancestral host eukaryotic cells and established a persistent symbiotic relationship.

Cytoskeleton

An extensive network of structural protein fibers extending throughout the eukaryotic cytoplasm that provides mechanical support, anchors organelles, and enables cell motility.

Microtubules

The thickest fibers of the cytoskeleton, composed of tubulin protein, that form cilia, flagella, mitotic spindles, and transport tracks for motor proteins.

Microfilaments

Thin protein filaments composed of actin that drive muscle cell contraction, cytoplasmic streaming, and changes in cellular shape.

Intermediate filaments

Permanent, ropelike fibrous protein strands that provide tensile strength to reinforce cell shape and anchor specific organelles (such as the nucleus) in place.

Cilia

Short, numerous microtubule-containing projections on the eukaryotic cell surface that beat synchronously in a coordinated paddle-like motion.

Flagella

Long, typically singular or sparse cellular extensions composed of microtubules that propel eukaryotic cells via an undulating, whiplike motion.

Extracellular matrix

A dense meshwork of glycoproteins (such as collagen and integrins) located outside animal cells that binds cells into tissues and protects the plasma membrane.

Tight junctions

Animal cell junctions in which neighbouring plasma membranes are pressed tightly together, forming continuous, leak-proof seals that prevent fluid leakage across epithelial tissue.

Anchoring junctions

Mechanical cell junctions in animal tissues (also known as desmosomes) that fasten adjacent cells securely together into resilient sheets using intermediate filaments.

Gap junctions

Intercellular communication channels between animal cells that provide cytoplasmic pores allowing ions, sugars, and small molecules to pass directly from cell to cell.

Plasmodesmata

Open microscopic channels perforating adjacent plant cell walls that link cytoplasms directly, facilitating intercellular transport of water, solutes, and signaling molecules.