Cell Biology and Membrane Transport Vocabulary

Vocabulary flashcards covering cellular structures, organelles, active transport mechanisms, membrane potential, and vesicular transport based on lecture slides.

Antiporter

A carrier protein that transports one substance into the cell while transporting a different substance out of the cell.

Symporter

A carrier protein that transports two different substances across the plasma membrane in the same direction.

Primary Active Transport

Active membrane transport where the required energy to move solutes against their concentration gradient comes directly from ATP hydrolysis.

Secondary Active Transport

An active transport process (also called cotransport) driven indirectly by energy stored in ionic concentration gradients created by primary active transport.

Sodium-Potassium Pump

An essential membrane enzyme called $\text{Na}^+\text{-K}^+\text{ ATPase}$ that actively pumps $3\,\text{Na}^+$ out of the cell and $2\,\text{K}^+$ back into the cell per hydrolyzed molecule of ATP.

Vesicular Transport

The transport of large particles, macromolecules, and fluids across cellular membranes enclosed within membranous sacs called vesicles.

Endocytosis

A vesicular transport process in which substances are brought into the cell inside protein-coated vesicles.

Exocytosis

A cellular ejection process where material enclosed in a secretory vesicle is released outside the cell upon binding of v-SNARE proteins to target t-SNARE proteins.

Transcytosis

A vesicular transport process combining endocytosis, internal movement, and exocytosis to transport a substance into, across, and then out of a cell.

Vesicular Trafficking

The cellular transport process of moving substances in vesicles from one internal area or organelle to another.

Phagocytosis

A type of endocytosis referred to as "cell eating," where membrane projections called pseudopods flow around solid particles to form an internalized vesicle called a phagosome.

Pinocytosis

A type of endocytosis referred to as "cell drinking" or fluid-phase endocytosis, where the plasma membrane infolds to bring extracellular fluid and dissolved solutes inside the cell.

Receptor-Mediated Endocytosis

A selective endocytosis process where specific target molecules bind to plasma membrane receptors embedded in clathrin-coated pits or caveolae prior to internalization.

Resting Membrane Potential (RMP)

The electrical potential energy produced by the separation of oppositely charged ions across the plasma membrane in resting cells, ranging from $-50\,\text{mV}$ to $-100\,\text{mV}$.

Cell Adhesion Molecules (CAMs)

Sticky glycoprotein molecules projecting from the cell membrane that anchor cells, assist in cellular movement, attract white blood cells, and transmit intracellular signals.

Cytosol

The gel-like fluid portion of the cytoplasm composed of water and dissolved solutes including proteins, salts, and sugars.

Inclusions

Insoluble chemical substances stored within the cytoplasm that vary by cell type, such as glycogen granules, pigments, lipid droplets, vacuoles, and crystals.

Mitochondria

Double-membrane enclosed organelles termed the "powerhouse" of the cell that synthesize most cellular ATP via aerobic respiration and contain their own DNA, RNA, and ribosomes.

Cristae

Infoldings of the inner mitochondrial membrane that contain embedded membrane proteins involved in cellular respiration.

Free Ribosomes

Unattached, free-floating ribosomes in the cytosol that synthesize soluble proteins used within the cytosol and specific organelles.

Membrane-Bound Ribosomes

Ribosomes attached to the endoplasmic reticulum membrane that synthesize lysosomal proteins, membrane-bound proteins, or proteins destined for export from the cell.

Rough Endoplasmic Reticulum (RER)

A membranous network studded with attached ribosomes that synthesizes secreted proteins, plasma membrane proteins, and phospholipids.

Smooth Endoplasmic Reticulum (SER)

A network of looped tubules continuous with rough ER containing enzymes for lipid and steroid synthesis, chemical detoxification, glycogen conversion, and calcium storage.

Golgi Apparatus

A stack of flattened membranous cisternae that receives proteins at its cis face from the rough ER, then modifies, concentrates, packages, and secretes them from its trans face.

Peroxisomes

Membranous sacs containing oxidase and catalase enzymes that neutralize toxic free radicals and convert hydrogen peroxide ($\text{H}_2\text{O}_2$) into harmless water.

Lysosomes

Spherical membranous bags containing acid hydrolases that digest ingested particles, degrade nonfunctional organelles, and cause autolysis in injured cells.

Cytoskeleton

An elaborate network of protein rods throughout the cytosol—comprising microfilaments, intermediate filaments, and microtubules—that provides structural support and enables movement.

Microfilaments

The thinnest cytoskeletal elements ($\sim 7\,\text{nm}$ thick), composed of actin protein strands that strengthen the cell surface, resist compression, and participate in cell motility.

Intermediate Filaments

Tough, insoluble protein fibers ($\sim 10\,\text{nm}$ thick) constructed from four tetramer fibrils coiled together that help cells resist pulling forces.

Microtubules

Hollow cytoskeletal tubes ($\sim 25\,\text{nm}$ thick) composed of tubulin protein subunits that determine overall cell shape and serve as tracks for organelle movement.

Motor Proteins

ATP-powered protein complexes, such as kinesin and cytoplasmic dynein, that transport organelles and cellular cargo along cytoskeletal tracks.

Centrosome

A microtubule organizing center located near the nucleus containing a granular matrix and a pair of barrel-shaped centrioles positioned at right angles to each other.

Cilia

Whiplike, motile extensions composed of microtubules that beat in a coordinated sweeping motion to move substances across cell surfaces.

Flagella

Long cellular extensions made of microtubules that propel an entire cell through its environment, such as the tail of a sperm cell.

Microvilli

Fingerlike projections of the plasma membrane containing a core of actin microfilaments that increase cell surface area for absorption.

Nuclear Envelope

A double-membrane barrier enclosing the nucleoplasm whose outer layer is continuous with the rough ER and inner layer is lined by the nuclear lamina.

Nucleolus

A dark-staining spherical body within the nucleus involved in ribosomal RNA (rRNA) synthesis and ribosome subunit assembly.

Chromatin

Fundamental genetic material composed of nucleosomes—DNA wrapped around histone proteins—that condenses into chromosomes during cell division.