Cell Structure, Function, Membrane Transport, and Cell Signaling

Vocabulary practice flashcards covering cell structure, organelles, plasma membrane properties, passive and active transport, cellular junctions, and cell communication pathways.

Cell Theory

The unifying biological concept stating that cells are the basic living units of organization and function in all organisms, and that all cells come from other cells.

Cell Homogenate

The mixture produced when cells are disrupted blender-style prior to sub-cellular fractionation.

Centrifugation

A biochemical technique used to fractionate disrupted cell components by separating them based on size and mass.

Nucleoid

The nuclear-like region in a prokaryotic cell where DNA is located, lacking a surrounding membrane.

Endomembrane System

A class of eukaryotic organelles that communicate with one another via membrane channels or small vesicles.

Energy-related Organelles

A class of independent and self-sufficient eukaryotic organelles, specifically mitochondria and chloroplasts, responsible for cellular energy conversions.

Endosymbiotic Theory

The theory stating that energy organelles, such as mitochondria and chloroplasts, originated when larger cells engulfed smaller prokaryotic cells.

Nuclear Envelope

A double membrane structure that separates the nuclear contents from the cytoplasm.

Nuclear Pores

Structures in the nuclear envelope that regulate the passage of materials between the nucleoplasm and cytoplasm.

Nucleolus

A specialized region inside the nucleus where ribosomes are manufactured.

Ribosomes

Organelles found free in the cytoplasm or attached to membranes that contain enzymes forming peptide bonds to join amino acids into polypeptides.

Smooth ER

Endoplasmic reticulum that synthesizes phospholipids and cholesterol to form membranes and breaks down toxins.

Rough ER

Endoplasmic reticulum studded with ribosomes that synthesizes secreted and membrane proteins.

Cis Face

The entry region of a Golgi stack that receives incoming transport vesicles.

Trans Face

The exit region of a Golgi stack where processed molecules depart.

Lysosomes

Small sacs of digestive enzymes in animal cells, produced by the Golgi complex, that maintain an internal pH of about $5$ to break down waste, debris, and bacteria.

Peroxisomes

Organelles that break down fatty acid molecules through oxidation reactions producing $H_2O_2$ and synthesize plasmalogens.

Plasmalogens

Phospholipids synthesized by peroxisomes that play important roles in antioxidant function and brain myelin formation.

Chlorophyll

The green pigment in chloroplasts that absorbs light energy for photosynthesis along with light-absorbing yellow and orange pigments.

Stroma

The fluid-filled space (aka cytoplasm) enclosed by the inner membrane of a chloroplast containing enzymes that produce carbohydrates from $CO_2$ and $H_2O$.

Microtubules

Hollow cylinders composed of tubulin dimers that support the cytoskeleton, participate in cell division, act as tracks for intracellular transport, and aid cell movement.

Kinesin

A motor microtubule-associated protein that transports organelles and vesicles toward the plus end of a microtubule (anterograde movement).

Dynein

A motor microtubule-associated protein that transports organelles and vesicles toward the minus end of a microtubule (retrograde movement).

Microtubule-Organizing Centers (MTOCs)

Structures, such as centrosomes, that anchor the minus ends of microtubules to other parts of the cell.

Integral Proteins

Amphipathic membrane proteins that are firmly bound and partially or wholly embedded across the phospholipid bilayer.

Peripheral Proteins

Membrane proteins located on the inner or outer surface of the plasma membrane, bound to exposed regions of integral proteins.

Glycoproteins

Proteins with attached carbohydrate chains on the extracellular surface of the membrane that aid in cellular recognition and fingerprinting.

Glycolipids

Lipids with attached carbohydrate chains located on the outer surface of the plasma membrane.

Amphipathic Molecules

Molecules having both nonpolar hydrophobic regions (such as fatty acid chains) and polar hydrophilic regions (such as phosphate groups).

Fluidity Buffer

The function of cholesterol in membranes that maintains chain fluidity at low temperatures and stabilizes them at high temperatures.

Porins

Transmembrane channel proteins that allow solutes or water to pass through biological membranes.

Aquaporins

Gated transmembrane water channels that allow rapid transport of water through the plasma membrane.

Osmosis

The diffusion or net movement of water molecules across a membrane from a region of higher water concentration to a region of lower water concentration.

Isotonic Solution

A fluid environment in which the solute concentration is equal to that inside the cell, resulting in no net movement of water.

Hypertonic Solution

A solution with a higher concentration of solutes than the cell cytoplasm, causing water to move out of the cell and the cell to shrink.

Hypotonic Solution

A solution with a lower concentration of solutes than the cell cytoplasm, causing water to enter the cell and the cell to swell.

Turgor Pressure

Internal pressure exerted by water inside a plant cell that supports the plant structure and halts net water movement into the cell.

Plasmolysis

The separation and shrinking of the plasma membrane away from the cell wall when a plant cell is placed in a hypertonic solution.

Sodium-Potassium Pump

An active transport carrier protein that expends energy from one ATP molecule to export three $Na^+$ ions out of the cell and import two $K^+$ ions into the cell.

Exocytosis

An active transport process where vesicles export large molecules out of the cell by fusing with the plasma membrane.

Endocytosis

An active transport process in which the cell imports materials by phagocytosis, pinocytosis, or receptor-mediated endocytosis.

Phagocytosis

A form of endocytosis in which a cell ingests large solid particles by forming plasma membrane folds that enclose the particle into a vacuole or phagosome.

Pinocytosis

A form of endocytosis in which droplets of fluid containing dissolved materials are trapped by plasma membrane folds that pinch off into the cytosol as vesicles.

Desmosomes

Specialized adhesive protein complexes anchored to intermediate filaments that serve as points of attachment holding cells together tightly at a single spot.

Tight Junctions

Connections between cell membranes so tight that no space remains between cells, effectively sealing off body cavities.

Gap Junctions

Intercellular connections containing connexons that allow direct communication and transfer of small molecules and ions between adjacent animal cells.

Endocrine Signaling

Long-distance signaling in which specialized cells secrete hormones into the blood to be transported to target cells.

Autocrine Signaling

A signaling mechanism where a secreted signal molecule acts on the very cell that produced it.

Paracrine Signaling

Local cell signaling in which signal molecules diffuse through interstitial fluid to act on nearby target cells.

Juxtacrine Signaling

Cellular communication that requires direct physical contact between adjacent cells.

Ligand

A specific signaling molecule that binds precisely to a complementary receptor to initiate a response.

Kinase

An enzyme that transfers a phosphate group from ATP to a target protein, thereby turning the protein 'on'.

Phosphatase

An enzyme that catalyzes the removal of a phosphate group from a protein by hydrolysis, thereby turning the protein 'off'.

Cyclic AMP (cAMP)

A derivative of ATP that acts as a common intracellular second messenger to amplify signaling cascades.

Ion Channel-Linked Receptors

Cell surface transmembrane protein receptors that convert chemical signals into electrical signals by opening or closing ion channels upon ligand binding.

G Protein-Coupled Receptors

Transmembrane receptors featuring an extracellular binding site for a signaling molecule and an intracellular binding site for a specific G protein.

Tyrosine Kinase

An enzymatic domain or receptor that catalyzes the transfer of phosphate groups from ATP to specific tyrosine residues on a protein.

Transcription Factors

Regulatory proteins or ligand-receptor complexes that bind to specific regions of DNA to activate or repress gene expression.