Cell Structure, Function, and Biology

Vocabulary flashcards covering the history of cell discovery, cell theory, prokaryotic morphology and appendages, eukaryotic organelles, the endomembrane system, energy organelles, and cytoskeletal components.

Robert Hooke

Scientist who in 1665 examined a thin slice of cork under a microscope, observed small box-like structures, and named them "cells" after the rooms that monks lived in.

Anton Van Leeuwenhoek

Dutch microscope maker who in 1673 was the first to observe living organisms under a simple, handheld microscope using pond water and teeth scrapings.

Matthias Schleiden

German botanist who concluded in 1838 that all plants are made of cells, serving as a co-founder of cell theory.

Theodore Schwann

German zoologist who concluded in 1839 that all animals are made of cells, serving as a co-founder of cell theory.

Rudolph Virchow

German medical doctor who observed cells dividing under the microscope in 1855 and reasoned that all cells arise from pre-existing cells via cell division.

Cell Theory

Fundamental biological theory stating that all living things are made of cells, cells are the basic unit of structure and function in an organism, and cells arise only from the reproduction of existing cells.

Virus

A nonliving, disease-causing particle composed of an inner core of nucleic acid enclosed by one or two protein coats; it reproduces only within living cells and cannot maintain homeostasis.

Plasmids

Accessory rings of prokaryotic DNA that serve a role in biotechnology as vectors to transport genes from organism to organism.

Mesosome

An inward fold of the prokaryotic plasma membrane that extends into the cytoplasm to increase internal surface area.

Glycocalyx

A gel-like coating outside the bacterial cell wall; classified as a capsule when compact and well-organized, or a slime layer when diffuse.

Fimbriae

Hairlike, bristle-like protein fibers on bacterial cell surfaces that allow attachment and adhesion to surfaces; also called attachment pili.

Conjugation Pilus

An elongated, rigid, hollow tubular appendage used by bacteria to pass DNA to other bacterial cells during genetic recombination.

Inclusion Body

A prokaryotic cytoplasmic structure used to store reserve nutrients for later metabolic use.

Endosymbiotic Theory

The evolutionary model proposing that eukaryotic organelles, specifically mitochondria and chloroplasts, originated when ancestral eukaryotic cells engulfed aerobic and photosynthetic bacteria.

Chromatin

Diffuse, uncoiled threads of DNA and associated proteins visible throughout the nucleoplasm when a cell is not dividing.

Nucleolus

A specialized dark-staining region within the eukaryotic nucleus where ribosomal RNA ($rRNA$) is produced.

Nuclear Envelope

A double membrane that separates the nucleus from the cytoplasm, penetrated by nuclear pores that regulate the transport of $RNA$ and ribosomal subunits.

Signal Recognition Particle (SRP)

A ribonucleoprotein complex that binds to the signal peptide of a newly synthesized protein on a ribosome and docks it to a receptor on the endoplasmic reticulum membrane.

Rough Endoplasmic Reticulum (RER)

A system of membranous channels and saccules continuous with the nuclear envelope and studded with ribosomes; synthesizes membrane proteins and secretory proteins.

Smooth Endoplasmic Reticulum (SER)

A tubular membranous organelle lacking ribosomes; synthesizes lipids and steroid hormones, detoxifies drugs and poisons, and regulates calcium in muscle cells.

Golgi Apparatus

A stack of flattened saccules that receives transport vesicles at its cis face, enzymatically modifies their protein contents, and packages them into vesicles leaving from the trans face.

Lysosomes

Low-pH, membrane-bound digestive vesicles produced by the Golgi apparatus that contain hydrolytic enzymes to break down food, bacteria, and worn-out cell parts.

Autolysis

Programmed cell destruction in which lysosomes break open and release their digestive enzymes into the cell to degrade and recycle cellular components.

Peroxisomes

Membrane-bound metabolic vesicles containing enzymes that produce hydrogen peroxide ($H_2O_2$), which is subsequently broken down by catalase into water and oxygen.

Central Vacuole

A large fluid-filled plant organelle occupying approximately $90\%$ of cell volume; contains cell sap to maintain turgor pressure and stores nutrients, pigments, and wastes.

Chloroplasts

Three-membrane photosynthetic organelles in plants and algae featuring an outer membrane, an inner membrane, a fluid stroma, and thylakoid sacs stacked into grana.

Chromoplasts

Plastids that synthesize and store red, orange, and yellow pigments in plant cells.

Leucoplasts

Colorless plant plastids that synthesize and store starches and oils.

Mitochondria

Double-membrane energy organelles whose inner membrane is folded into cristae enclosing a fluid matrix containing enzymes that break down carbohydrates to produce $ATP$.

Actin Filaments

Long, thin, flexible protein fibers consisting of two chains of globular actin monomers wound in a helix; interact with myosin to produce cellular motion.

Intermediate Filaments

Rope-like assemblies of fibrous polypeptides, such as keratin, that provide mechanical support to the nuclear envelope and form cell-to-cell junctions.

Microtubules

Small hollow cylinders made of $\alpha$ and $\beta$ tubulin heterodimers arranged in rows; serve as tracks for organelle movement and form the mitotic spindle.

Centrosome

The primary microtubule organizing center (MTOC) in animal cells that regulates the assembly of microtubules.

Centrioles

Paired barrel-shaped structures in animal cells and protists containing a $9+0$ pattern of microtubule triplets around an empty center; replicate before division and organize the spindle.

Cilia and Flagella

Hairlike, motile cellular projections containing a $9+2$ arrangement of microtubule doublets powered by motor molecules that slide adjacent doublets past each other.

Basal Body

A cytoplasmic structure located at the base of cilia and flagella composed of a $9+0$ arrangement of microtubule triplets that directs their organization.

Colchicine

A plant-derived poison that disrupts cellular processes by preventing the assembly and polymerization of microtubules.