Chapter 3 Part A: Cells—The Living Units (Vocabulary)

Vocabulary flashcards covering key terms from the Cells: The Living Units notes.

Cell theory

A cell is the structural and functional unit of life; the organism’s function depends on the activities of its cells; cells arise only from preexisting cells.

Biogenesis

Cells can arise only from other preexisting cells.

Cell diversity

Over 250 human cell types differing in size, shape, and subcellular components, leading to varied functions.

Generalized cell

A conceptual model of a cell with three basic parts: plasma membrane, cytoplasm, and nucleus.

Plasma membrane

Flexible outer boundary that encloses the cell, separates ICF from ECF, and controls entry/exit.

Cytoplasm

Intracellular fluid containing organelles.

Nucleus

DNA-containing control center of the cell.

Interstitial fluid

Fluid bathing tissue cells.

Blood plasma

Fluid component of blood.

Cerebrospinal fluid

Fluid surrounding nervous system organs.

Extracellular matrix

Substance outside cells that holds cells together.

Glycocalyx

Sugar-rich coating on the cell surface involved in cell recognition.

Fluid mosaic model

Membrane structure that is a dynamic, fluid mosaic of lipids and proteins.

Phospholipid bilayer

Two-layer membrane with polar heads and nonpolar tails forming the basic structure.

Cholesterol (membrane)

Steroid that stiffens membrane and modulates fluidity (four-ring structure).

Glycolipids

Lipids with sugar groups on the outer membrane surface.

Glycoproteins

Proteins with carbohydrate chains; part of glycocalyx; involved in cell recognition.

Integral proteins

Proteins firmly inserted into membrane; often transmembrane; function as transporters, enzymes, or receptors.

Peripheral proteins

Proteins loosely attached to the membrane or to integral proteins; provide support and other roles.

Channel proteins

Integral proteins that form aqueous channels allowing ions or water to cross.

Carrier proteins

Transmembrane proteins that transport specific polar molecules by changing shape.

Receptor

Membrane protein that binds chemical messengers and initiates a cellular response.

Enzyme

Membrane protein with active site exposed to substances; may catalyze steps of a metabolic pathway.

CAMs (cell adhesion molecules)

Membrane proteins that enable cell-to-cell binding and guide cell migration.

Cytoskeleton

Internal framework that supports cell shape and anchors membrane proteins; helps movement.

Cadherins

Desmosome linker proteins that interlock neighboring cells and connect to keratin filaments for strength.

Connexons

Transmembrane proteins that form gap junction channels.

Tight junctions

Junctions formed by fused integral proteins; create an impermeable barrier between cells.

Desmosomes

Rivet-like junctions with cadherins and keratin networks; provide strength.

Gap junctions

Direct cell-to-cell communication via connexons; allow ions and small molecules to pass.

Aquaporin

Water channel protein that facilitates osmosis.

Simple diffusion

Passive diffusion of lipid-soluble or very small molecules directly through the lipid bilayer.

Facilitated diffusion

Passive transport aided by carriers or channels for molecules that cannot cross the bilayer easily.

Osmosis

Diffusion of water across a selectively permeable membrane.

Osmolarity

Total concentration of solute particles in solution; expressed in osmol/L.

Isotonic

Solution with osmolarity equal to that inside the cell; no net water movement.

Hypertonic

Solution with higher osmolarity outside; water moves out; cell crenates (shrinks).

Hypotonic

Solution with lower osmolarity outside; water moves in; cell swells and may lyse.

Crenation

Shrinking of a cell in a hypertonic solution.

Lysing

Cell bursting due to swelling in a hypotonic solution.

Hydrostatic pressure

Outward pressure on the cell side due to volume increase from osmosis.

Osmotic pressure

Inward pressure due to water being drawn into a solution with higher solute concentration.

Tonicity

Ability of a solution to change cell volume by water movement.

Saturation

Carriers become saturated when all are bound and busy transporting; maximum transport rate.

Polar hydrophilic head

Phospholipid head that is polar and water-loving.

Nonpolar hydrophobic tail

Phospholipid tail that is nonpolar and water-hating.