Cell Biology: Cell Structure, Function, and Membrane Dynamics

Vocabulary practice flashcards covering cell structure, organelles, transport, microscopy, cytoskeleton, junction types, and plasma membrane dynamics.

Peripheral Proteins

Membrane proteins that are loosely bound to the surface of the cell membrane.

Integral Proteins

Membrane proteins that penetrate the hydrophobic core of the lipid bilayer, often containing hydrophobic regions of nonpolar amino acids coiled into $\alpha$ helices.

Transmembrane Proteins

Integral proteins that span completely across the cellular membrane.

CCR5 Co-receptor

A cell-surface protein that HIV must bind to along with CD4 to infect immune cells; individuals lacking CCR5 are immune to HIV infection.

Cholesterol (in Membranes)

A steroid component in animal cell membranes that restrains phospholipid movement at warm temperatures ($37^\circ\text{C}$) and maintains fluidity at cool temperatures by preventing tight packing.

Magnification

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

Resolution

The measure of image clarity in microscopy, defined as the minimum distance between two distinguishable points.

Contrast

The visible difference in brightness between parts of a sample in microscopy.

Scanning Electron Microscope (SEM)

A microscope that focuses an electron beam onto the surface of a specimen, providing three-dimensional images of its topography.

Transmission Electron Microscope (TEM)

A microscope that passes an electron beam through a specimen, used primarily to study internal cellular structures.

Cryo-electron Microscopy (cryo-EM)

A technique that preserves specimens at very low temperatures without chemical preservatives, allowing visual inspection of cellular structures in their natural state.

Cell Fractionation

A laboratory procedure using centrifuges (differential centrifugation) to separate cell components and major organelles for biochemical analysis.

Nucleoid

An unbound nuclear region in a prokaryotic cell where its DNA is concentrated.

Nuclear Envelope

A double-membrane barrier that encloses the cell nucleus, separating its contents from the cytoplasm.

Nuclear Lamina

A protein filament network lining the inner nuclear envelope that structurally maintains the shape of the nucleus.

Nucleolus

A prominent structure inside the non-dividing nucleus where ribosomal RNA (rRNA) synthesis occurs.

Chromatin

The complex of DNA and associated proteins (histones) that forms eukaryotic chromosomes.

Smooth ER

A region of the endoplasmic reticulum lacking ribosomes that synthesizes lipids, detoxifies drugs and poisons, and stores calcium ions.

Rough ER

A region of the endoplasmic reticulum studded with ribosomes that secretes glycoproteins, manufactures membrane material, and packages transport vesicles.

Golgi Apparatus

An organelle composed of flattened membranous sacs (cisternae) with distinct cis (receiving) and trans (shipping) faces that modifies, sorts, and packages products from the ER.

Lysosome

A membranous organelle containing hydrolytic enzymes used to digest macromolecules in an acidic internal environment.

Phagocytosis

A process by which a cell engulfs another cell or food particle to form a food vacuole that subsequently fuses with a lysosome.

Autophagy

A cellular recycling process where lysosomes use hydrolytic enzymes to break down damaged organelles and cytosolic components.

Contractile Vacuole

A specialized organelle found in freshwater protists that collects and pumps excess water out of the cell.

Central Vacuole

A large plant organelle containing cell sap that stores inorganic ions (such as potassium and chloride) and promotes cell growth.

Endosymbiont Theory

An evolutionary theory proposing that mitochondria and chloroplasts originated as prokaryotic cells engulfed by an early eukaryotic host cell.

Cristae

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

Mitochondrial Matrix

The compartment enclosed by the inner membrane of a mitochondrion, housing mitochondrial DNA, ribosomes, and respiration enzymes.

Thylakoids

Flattened, interconnected sacs inside a chloroplast where light energy is converted into chemical energy; stacked together, they form grana.

Stroma

The fluid portion of the chloroplast surrounding the thylakoid membrane, containing chloroplast DNA, ribosomes, and photosynthetic enzymes.

Peroxisomes

Single-membrane metabolic compartments that remove hydrogen atoms from substrates and attach them to oxygen, forming hydrogen peroxide.

Glyoxysomes

Specialized peroxisomes in plant seed tissues that convert stored fatty acids into sugars to support seedling growth.

Microtubules

Hollow rods composed of tubulin dimers measuring $25\,\text{nm}$ in diameter that maintain cell shape, move organelles, and separate chromosomes during cell division.

Centrosome

A structure near the nucleus of animal cells functioning as a microtubule-organizing center, containing two perpendicular centrioles.

Centriole

A cylinder structure in the centrosome composed of nine triplets of microtubules arranged in a ring.

Dynein

A motor protein with two ATP-powered feet that walk along microtubules, driving the bending motions of motile cilia and flagella.

Basal Body

A structure composed of microtubule triplets that anchors the base of a cilium or flagellum within the cell.

Microfilaments

Solid cytoskeletal rods measuring $7\,\text{nm}$ in diameter, built from a double chain of actin subunits, responsible for cell motility, microvilli structure, and muscle contraction.

Pseudopodia

Cellular extensions driven by microfilament assembly that allow cells such as amoebas to crawl along surfaces.

Cytoplasmic Streaming

A circular flow of cytoplasm within plant cells mediated by actin-myosin interactions that speeds up internal distribution of materials.

Intermediate Filaments

Fibrous cytoskeletal cables measuring $8\text{--}12\,\text{nm}$ in diameter (including keratins) that provide permanent structural support, form the nuclear lamina, and anchor organelles.

Middle Lamella

An extracellular layer rich in pectin polysaccharides located between the primary walls of adjacent plant cells that cements them together.

Integrins

Cell-surface receptor proteins spanning the plasma membrane that link extracellular matrix proteins like fibronectin to the cytoskeleton.

Plasmodesmata

Cytoplasm-filled channels passing through plant cell walls that physically connect adjacent plant cells.

Tight Junctions

Intercellular junctions in animal epithelial tissues where plasma membranes are tightly pressed together to block leakage of fluids across cell layers.

Desmosomes

Anchoring junctions in animal tissue that rivet cells together into tough sheets, tethered internally by intermediate filaments.

Gap Junctions

Communicating intercellular junctions in animal cells consisting of membrane channels that allow ions and small molecules to pass between cells.