Cell Biology & Membrane Transport Vocabulary

Comprehensive vocabulary flashcards covering cell structure, organelles, microscopy techniques, endomembrane function, cytoskeleton components, and membrane transport processes.

Light Microscope

A microscope where visible light passes through a specimen and then through glass lenses, which refract the light to magnify the specimen.

Magnification

The ratio of an object's image size to its real size.

Resolution

A measure of clarity, defined as the minimum distance two points can be separated and still be distinguished as separate ones.

Contrast

The difference in brightness between light and dark areas of an image, which can be enhanced by staining and labeling cell components.

Electron Microscope

A microscope that focuses a beam of electrons through a specimen, with resolution inversely related to wavelength.

Scanning Electron Microscope (SEM)

A microscope used to study the topography of a specimen using electromagnets as lenses.

Transmission Electron Microscope (TEM)

A microscope that profiles a thin section of a specimen with an electron beam to look at internal cell structure, using heavy metal atoms attached to parts of cells.

Cryo-electron Microscopy

A microscopy technique that preserves specimens at low temperatures and avoids the use of preservatives.

Cell Fractionation

A technique that takes cells apart and separates organelles from each other using a centrifuge.

Nuclear Envelope

A double membrane enclosing the nucleus, composed of lipid bilayers with associated proteins and perforated with pore structures.

Pore Complex

A structure that lines each nuclear pore and regulates the exit and entry of proteins, RNAs, and large macromolecule complexes.

Nuclear Lamina

An array of protein filaments that supports the nuclear envelope and maintains its shape.

Nuclear Matrix

A framework of protein fibers located inside the nucleus.

Chromatin

The complex of protein and DNA found in uncoiled chromosomes.

Nucleolus

A specialized structure within the nucleus that synthesizes rRNA and ribosome subunits.

Free Ribosomes

Ribosomes suspended in the cytosol that mostly synthesize proteins functioning within the cytosol (such as enzymes catalyzing sugar breakdown).

Bound Ribosomes

Ribosomes attached to the outside of the ER or nuclear envelope that synthesize proteins intended for membrane insertion, organelle packaging, or secretion.

Endomembrane System

A cellular network that modifies, packages, and transports proteins and lipids into and out of the cell.

Endoplasmic Reticulum (ER)

A membrane network consisting of cisternae (sacs/tubules) that separates the ER lumen (inner compartment) from the cytosol.

Smooth ER

The portion of the ER lacking ribosomes, responsible for lipid synthesis, drug and poison detoxification (adding $\text{-OH}$ groups), and calcium ion storage.

Rough ER

The portion of the ER studded with ribosomes, involved in manufacturing secretory proteins (glycoproteins) and generating membrane proteins and phospholipids.

Golgi Apparatus

An organelle composed of cisternae stacks that receives, sorts, shifts, modifies, and dispatches proteins to other cell locations.

Cis Face (Golgi)

The receiving side of the Golgi apparatus where transport vesicles from the ER fuse with the Golgi membrane.

Trans Face (Golgi)

The shipping side of the Golgi apparatus that gives rise to transport vesicles heading to other destinations.

Cisternae Maturation Model

A theoretical model proposing that Golgi cisternae process and physically move from cis to trans, carrying and modifying cargo as they progress.

Lysosome

A membrane-bound sac of hydrolytic enzymes used to hydrolyze macromolecules, operating optimally in an acidic environment.

Phagocytosis

A process of cellular engulfment of smaller organisms or food particles, forming a food vacuole that subsequently fuses with a lysosome.

Autophagy

A recycling mechanism where lysosomes breakdown and dismantle damaged organelles and cellular organic material.

Tay-Sachs Disease

A genetic disorder caused by an inactive or missing lipid-digesting enzyme, resulting in an accumulation of lipids in cells.

Vacuole

A membrane-bound vesicle derived from the ER and Golgi apparatus that carries out varied metabolic functions.

Central Vacuole

A large organelle in plant cells filled with cell sap that serves as the main repository for inorganic ions such as $K^+$ and $Cl^-$.

Mitochondria

Organelles responsible for cellular respiration that utilize oxygen to drive ATP synthesis.

Chloroplasts

Photosynthetic organelles found in plant and algae cells that convert solar energy into chemical energy.

Endosymbiont Theory

The theory that an early eukaryote ancestor engulfed an oxygen-using non-photosynthetic prokaryote, which eventually became an integrated endosymbiont (mitochondrion or chloroplast).

Cristae

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

Mitochondrial Matrix

The fluid-filled inner compartment of a mitochondrion containing enzymes that catalyze steps of cellular respiration, along with mitochondrial DNA and ribosomes.

Thylakoids

Flattened, interconnected sacs stacked (as grana) inside chloroplasts that function in converting light energy into chemical energy.

Stroma

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

Plastids

A family of closely related plant organelles that includes chloroplasts, amyloplasts (starch storage), and chromoplasts (yellow/orange pigment storage).

Peroxisomes

Metabolic compartments containing enzymes that remove hydrogen atoms and transfer them to oxygen to produce $H_2O_2$, which is then converted into water.

Glyoxysomes

Specialized peroxisomes located in fat-storing tissues of plant seeds containing enzymes that convert fatty acids to sugar.

Cytoskeleton

A dynamic network of fibers extending throughout the cytoplasm that maintains cell shape and enables cell motility in conjunction with motor proteins.

Microtubules

Hollow rods composed of tubulin dimers ($\text{α-tubulin}$ and $\text{β-tubulin}$) that support cell shape, guide organelle traffic, and form cilia, flagella, and centrioles.

Centrosome

A structure present in animal cells functioning as a microtubule-organizing center, containing a pair of centrioles.

Flagella and Cilia

Microtubule-containing cellular extensions used for movement or moving fluids across tissue surfaces; flagella move in an undulating motion, whereas cilia utilize alternating power and recovery strokes.

Basal Body

A structure that anchors and organizes the microtubule assembly of a cilium or flagellum.

Dynein

A motor protein with flexible 'feet' that drives the bending movements of cilia and flagella.

Microfilaments (Actin Filaments)

Thin, solid rods composed of twisted double chains of actin subunits that bear tension and form the semi-solid cortex of the cell.

Intermediate Filaments

Fibrous cytoskeletal components intermediate in size between microtubules and microfilaments that specialize in bearing mechanical tension.

Middle Lamella

A thin layer rich in pectins located between primary cell walls of adjacent plant cells, gluing them together.

Extracellular Matrix (ECM)

A meshwork surrounding animal cells consisting of glycoproteins (such as collagen embedded in proteoglycan) and carbohydrate-containing molecules.

Integrins

Transmembrane receptor proteins that attach ECM components like fibronectin to the cytoskeleton, relaying signals across the cell membrane.

Plasmodesmata

Channels passing through plant cell walls that connect adjacent cytoplasm, permitting water and small solutes to pass freely.

Tight Junctions

Intercellular junctions in animal cells that form continuous, liquid-tight seals preventing extracellular fluid leakage.

Desmosomes

Anchoring junctions in animal cells that rivet adjacent cells together into strong structural sheets.

Gap Junctions

Communicating junctions in animal cells that provide cytoplasmic channels between cells for ions, sugars, and amino acids.

Fluid Mosaic Model

A model describing membrane architecture as a mosaic of protein molecules floating laterally within a fluid phospholipid bilayer.

Amphipathic

A property of a molecule possessing both hydrophilic (water-loving) and hydrophobic (water-fearing) regions.

Integral Proteins

Membrane proteins embedded within the hydrophobic core of the lipid bilayer, typically possessing nonpolar amino acids arranged in $\text{α-helices}$.

Transmembrane Proteins

A class of integral proteins that completely span across the cell membrane.

Peripheral Proteins

Proteins loosely attached to the extracellular or cytoplasmic surface of the lipid bilayer.

Selective Permeability

The feature of biological membranes allowing nonpolar/hydrophobic molecules ($O_2$, $CO_2$, lipids) to cross easily while restricting ions and polar molecules.

Aquaporins

Specific channel proteins that facilitate the rapid diffusion of water molecules across cell membranes.

Diffusion

The passive movement of particles from an area of higher concentration to lower concentration down a concentration gradient.

Osmosis

The diffusion of free water across a selectively permeable membrane from lower solute concentration to higher solute concentration.

Tonicity

The capability of a surrounding solution to influence net water movement, causing a cell to gain or lose water.

Isotonic Solution

A solution whose solute concentration is equal to that of the cell interior, resulting in no net water movement and stable cell volume.

Hypertonic Solution

A solution with a higher solute concentration than the cytoplasm, drawing water out of the cell and causing it to shrivel.

Hypotonic Solution

A solution with a lower solute concentration than the cytoplasm, forcing water into the cell and causing it to swell or lyse.

Osmoregulation

The physiological regulation of solute concentrations and water balance in organisms.

Turgor Pressure

The back-pressure exerted by water within a plant cell against its cell wall, keeping the cell turgid (firm).

Plasmolysis

The pulling away of the plasma membrane from the cell wall in plant cells exposed to a hypertonic environment, causing wilting.

Facilitated Diffusion

The passive transport of polar molecules or ions across a membrane mediated by transport proteins.

Active Transport

The movement of a solute across a cell membrane against its concentration gradient, requiring energy input from ATP hydrolysis.

Sodium-Potassium Pump

An active transport system that expels $3\,\text{Na}^+$ ions out of the cell and imports $2\,\text{K}^+$ ions into the cell using ATP.

Membrane Potential

The voltage difference across a cell membrane created by an uneven distribution of anions and cations, maintaining a negative cytoplasmic charge relative to the extracellular side.

Electrogenic Pump

A transport protein that generates membrane potential during ion translocations, such as a proton pump transferring $H^+$ out of the cell.

Cotransport

A mechanism in which a transport protein couples the downhill diffusion of one solute to the simultaneous active transport of another against its concentration gradient.

Exocytosis

The process of cell secretion wherein transport vesicles fuse with the plasma membrane to release their contents outside the cell.

Endocytosis

The process of taking substances into the cell by invagination and pinching off of the plasma membrane to form vesicles.

Pinocytosis

A form of endocytosis where the cell engulfs droplets of extracellular fluid into small vesicles.

Receptor-Mediated Endocytosis

A selective endocytic process where specific ligand molecules bind to surface receptor proteins, triggering localized vesicle formation.