Cell Biology, Organelles, and Membrane Dynamics Vocabulary

Vocabulary practice flashcards covering molecular components, cellular organelles, plasma membrane structure, and intercellular junctions.

Hydrophilic

Describing a substance that is attracted to water and dissolves readily in polar environments.

Hydrophobic

Describing a nonpolar substance that is repelled by water and insoluble in aqueous solutions.

Amphipathic

Describing a large molecule containing both hydrophilic (water-attracted) and hydrophobic (water-repelled) regions, such as phospholipids.

Electrolytes

Ions formed when inorganic salts dissociate in water, enabling electrical conductivity within the body (e.g., $\text{Na}^+$, $\text{Cl}^-$, $\text{Ca}^{2+}$, and $\text{K}^+$).

pH Scale

A measurement scale for acidity or alkalinity where a neutral solution measures $7$, acidic solutions rate below $7$ ($1\text{--}6.9$), and basic (alkaline) solutions rate above $7$ ($7.1\text{--}14$).

Carbohydrates

Organic macromolecules made of sugar monomers that serve as the body's primary energy source.

Glycogen

A branched polymer of glucose subunits used by animals for glucose and energy storage in tissues such as the liver and muscles.

Nucleic Acids

Organic macromolecules constructed from nucleotide monomers, consisting of DNA (which stores genetic information) and RNA (which transfers genetic information).

Lipids

Hydrophobic organic macromolecules—not composed of monomers—that provide long-term energy storage in adipose tissue, form structural components, and make up certain hormones.

Proteins

Organic macromolecules constructed from amino acid monomers linked by peptide bonds that fulfill extensive roles including enzymatic catalysis, structural support, immune defense, and muscle contraction.

Enzymes

Protein catalysts that facilitate and accelerate chemical reactions in the body without being altered or consumed in the reaction.

Cytoplasm

The cellular material occupying the region between the plasma membrane and the nucleus, composed of cytosol, organelles, and chemical inclusions.

Cytosol

The viscous fluid portion of the cytoplasm composed largely of water with dissolved proteins, salts, sugars, and solutes.

Inclusions

Non-living chemical substances stored within the cytoplasm, such as pigment granules (melanin) or nutrient storage polymers (glycogen).

Mitochondria

Double-membrane organelles containing inner shelf-like cristae that generate cellular energy ($\text{ATP}$) via aerobic cellular respiration and possess their own DNA and RNA.

Cristae

The internal membrane folds of the inner mitochondrial membrane that maximize surface area for chemical reactions producing $\text{ATP}$.

Ribosomes

Non-membrane bound granules composed of protein and ribonucleic acid ($\text{RNA}$) that serve as the site of cellular protein synthesis.

Free Ribosomes

Unattached ribosomes floating freely in the cytosol that synthesize soluble proteins intended for internal use within the cell.

Rough Endoplasmic Reticulum

A membrane-bound system of interconnected sacs studded with ribosomes that manufactures proteins destined for cellular membranes, lysosomal enzymes, or exocytosis export.

Smooth Endoplasmic Reticulum

A continuous extension of the rough ER lacking ribosomes that synthesizes lipids and steroid hormones, detoxifies poisons, and regulates glycogen metabolism.

Cisternae

The fluid-filled internal cavities and spaces enclosed by the membranes of the endoplasmic reticulum and Golgi apparatus.

Golgi Apparatus

An organelle consisting of stacked, flattened membranous sacs that modifies, concentrates, and packages proteins received from the rough ER into vesicles.

Lysosomes

Spherical membranous organelles containing acidic fluid and hydrolytic digestive enzymes that break down pathogens, damaged cellular organelles, glycogen, and bone matrix.

Cytoskeleton

An internal cellular framework consisting of microfilaments, intermediate filaments, and microtubules that supports cell structure, moves materials, and aids in cell division.

Microfilaments

Thin $7\,nm$ protein strands (primarily actin) attached to the cytoplasmic side of the plasma membrane that strengthen the cell surface, enable motility, and facilitate cell shape changes.

Intermediate Filaments

Tough, insoluble rope-like protein fibers of $10\,nm$ diameter (e.g., keratin) that provide high tensile strength to resist mechanical pulling forces on the cell.

Microtubules

Large, hollow $25\,nm$ tubes constructed of spherical tubulin subunits anchored at the centrosome that determine cell shape, distribute organelles, and construct cilia and flagella.

Centrosome

The specialized cytoplasmic region located near the nucleus that acts as the microtubule organizing center and houses a pair of centrioles.

Centrioles

Small barrel-shaped organelles composed of microtubule triplets located within the centrosome that assemble mitotic spindle fibers during cell division.

Cilia

Motile, hair-like cellular projections on exposed cell surfaces that move extracellular substances in one direction across the surface.

Flagella

Long, singular cellular projections (such as the sperm tail) that move to propel the cell through fluid environments.

Microvilli

Non-mobile finger-like foldings of the plasma membrane reinforced by microfilaments that increase surface area for cellular absorption and secretion.

Plasma Membrane

A selectively permeable fluid bilayer of phospholipids and interspersed proteins that encloses intracellular contents and separates them from extracellular fluid.

Integral Proteins

Transmembrane proteins that span across the full width of the phospholipid bilayer to function as transport channels, carriers, and signal receptors.

Peripheral Proteins

Proteins attached loosely to the inner or outer surface of the plasma membrane that serve as enzymes, cell-to-cell links, or recognition markers.

Glycocalyx

The carbohydrate-rich coating on the outer cell surface composed of glycolipids and glycoproteins that functions as a unique cellular identification fingerprint.

Tight Junction

A cell junction formed by fused adjacent integral proteins that creates an impermeable seal between neighboring cells, preventing fluid leakage (e.g., in digestive tract epithelium).

Desmosome

An anchoring cell junction featuring interlocking protein plaques and intermediate filaments arranged like a zipper to distribute tension and prevent tissue tearing.

Gap Junction

A communicating cell junction composed of hollow protein channels (connexons) bridging adjacent cells to allow direct passage of ions and small molecules.