A Tour of the Cell - Vocabulary Flashcards

Vocabulary practice flashcards covering cytology, cell theory, microscopy, cellular organelles, the endomembrane system, cytoskeleton, and cell junctions based on lecture notes.

Cell Theory

The foundational biological concept stating that all organisms are made up of cells, the cell is the fundamental unit of life, and all cells come from preexisting cells.

Resolution

The minimum distance between two distinguishable points in microscopy, which is inversely related to the wavelength used to visualize the specimen.

Magnification

The ratio of an object's image size under a microscope to its real, actual size.

Contrast

The visible difference in brightness between different parts of a microscopic sample.

Scanning Electron Microscopy (SEM)

A microscopy technique that focuses a beam of electrons onto the surface of a specimen to provide images that appear three-dimensional.

Transmission Electron Microscopy (TEM)

A microscopy technique that focuses a beam of electrons through a thin specimen, used primarily to study the internal structure of cells.

Cell Fractionation

A laboratory technique that takes cells apart and uses differential centrifugation to separate major organelles from one another based on size and density.

Prokaryotic Cell

A type of cell that lacks a nucleus and internal membrane-bound compartmentalization.

Eukaryotic Cell

A type of cell characterized by containing a membrane-bound nucleus housing genetic material and internal membrane-bound organelles.

Cytosol

The semifluid, jelly-like substance enclosed within the plasma membrane in which subcellular components are suspended.

Nucleoid

The non-membrane-enclosed region in a prokaryotic cell where its bacterial chromosome and genetic material are concentrated.

Fimbriae

Attachment structures located on the outer surface of some prokaryotic cells that help them adhere to surfaces or other cells.

Plasma Membrane

A selective phospholipid bilayer barrier with embedded proteins that regulates the passage of materials into and out of the cell.

Ribosomes

Subcellular structures composed of ribosomal RNA and proteins, consisting of large and small subunits, that carry out protein synthesis.

Nucleus

The eukaryotic organelle that serves as the storehouse for the cell's genetic information and the site for RNA synthesis.

Nuclear Envelope

A double membrane perforated by pores that surrounds the eukaryotic nucleus and separates its contents from the cytoplasm.

Nucleolus

A prominent structure inside the eukaryotic nucleus involved in ribosomal RNA synthesis and ribosome assembly.

Endomembrane System

A collection of eukaryotic cellular membranes—including the nuclear envelope, ER, Golgi apparatus, lysosomes, vacuoles, and plasma membrane—that regulates protein traffic and performs metabolic functions.

Smooth Endoplasmic Reticulum

The region of the endoplasmic reticulum lacking bound ribosomes; it synthesizes lipids, metabolizes carbohydrates, detoxifies drugs and poisons, and stores calcium ions.

Rough Endoplasmic Reticulum

The region of the endoplasmic reticulum studded with bound ribosomes; it synthesizes proteins destined for membranes or secretion and distributes transport vesicles.

Golgi Apparatus

An organelle consisting of flattened membranous sacs that modifies, manufactures, sorts, and packages ER products into transport vesicles for final destinations.

Cisternae

Flattened, membrane-bound sacs that make up the structure of the Golgi apparatus and endoplasmic reticulum.

Lysosome

A membranous sac of hydrolytic enzymes that breaks down macromolecules such as proteins, nucleic acids, lipids, and carbohydrates.

Lysosomal Proton Pump

A membrane transport protein in the lysosome that actively pumps protons into its interior to maintain an acidic pH environment.

Vacuoles

Large membrane-bound vesicles derived from the ER and Golgi apparatus that perform functions such as food digestion, water balance, or storage.

Central Vacuole

A large vacuole found in mature plant cells that absorbs water, stores nutrients, and gives plants structural rigidity by contributing to turgor pressure.

Mitochondria

Double-membrane organelles that harness energy from chemical compounds such as sugars and convert it into ATP for the cell.

Cristae

Infoldings of the inner mitochondrial membrane that house electron transport chains and ATP synthesis proteins.

Mitochondrial Matrix

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

Chloroplasts

Triple-membrane-system organelles in plant and algal cells that capture the energy of sunlight to fix atmospheric carbon and synthesize simple sugars.

Thylakoid Membrane

The interior, third membrane system in chloroplasts where light-capturing reactions of photosynthesis take place.

Stroma

The dense fluid compartment enclosed by the inner membrane of a chloroplast, surrounding the thylakoid membrane system.

Granum

A stacked, disc-like structure composed of thylakoid membranes within a chloroplast.

Peroxisomes

Metabolic compartments containing enzymes that break down fatty acids and amino acids, producing hydrogen peroxide ($H_2O_2$) as a byproduct and converting it to water ($H_2O$).

Adenosine Triphosphate (ATP)

An organic molecule consisting of adenosine attached to three phosphate groups, serving as the primary energy currency of the cell.

Cytoskeleton

A network of protein filaments and associated proteins that provides the cell with an internal structural framework, organizes cell contents, and enables motility.

Microtubules

Hollow cylindrical cytoskeletal fibers measuring $25\,\text{nm}$ in diameter with a $15\,\text{nm}$ lumen, involved in cell shape maintenance, cell motility, chromosome movement, and organelle movement.

Tubulin

A globular protein dimer composed of $\alpha$ and $\beta$ subunits that polymerizes into $13$ columns to form the walls of microtubules.

Centrosome

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

Centrioles

A pair of cylindrical structures in animal cell centrosomes, each composed of nine sets of triplet microtubules arranged in a ring.

Microfilaments

Solid cytoskeletal rods measuring $7\,\text{nm}$ in diameter consisting of two intertwined strands of actin, involved in cell shape changes, muscle contraction, cytoplasmic streaming, and division.

Actin

A globular protein subunit that polymerizes into long double-stranded chains to form microfilaments.

Myosin

A motor protein that interacts with actin microfilaments to power muscle cell contraction and cell movement.

Cytoplasmic Streaming

A circular flow of cytoplasm within plant cells mediated by actin microfilaments that speeds up the distribution of materials throughout the cell.

Intermediate Filaments

Fibrous cytoskeletal cables measuring $8\,\text{nm to } 12\,\text{nm}$ in diameter composed of supercoiled proteins of the keratin family; functions in maintaining cell shape, anchoring organelles, and forming the nuclear lamina.

Plant Cell Wall

A rigid extracellular barrier composed of polysaccharides that maintains cell shape, provides structural protection, and prevents excessive water uptake in plant cells.

Plasmodesmata

Membrane-lined channels perforating plant cell walls that connect neighboring plant cells and unify their cytoplasm.

Extracellular Matrix (ECM)

An external meshwork surrounding animal cells composed of glycoproteins such as collagen, proteoglycan complexes, and fibronectin attached to cell surface integrins.

Tight Junctions

Intercellular connections in animal tissues that bind plasma membranes of neighboring cells tightly together, forming a continuous seal that prevents fluid movement across cell layers.

Gap Junctions

Intercellular communicating junction channels in animal tissues that allow direct passage of ions, sugars, and small molecules between adjacent cells.