Ch 4: Cell Structure and Membranes - Vocabulary Flashcards

A comprehensive set of vocabulary flashcards covering membranes, transport, vesicular trafficking, cytoskeleton, organelles, and extracellular structures from CHAPTER 4.

Fluid mosaic model

A model describing biological membranes as a dynamic, fluid phospholipid bilayer with embedded, anchored, and peripheral proteins arranged in a mosaic-like pattern.

Phospholipid bilayer

Two-layer sheet of phospholipids forming the hydrophobic interior of membranes, with hydrophilic heads facing outward and tails inward.

Amphipathic

Molecules that have both hydrophilic (water-loving) and hydrophobic (water-fearing) regions, enabling bilayer formation.

Integral membrane protein

A protein embedded in the lipid bilayer, often spanning the entire membrane (transmembrane) with hydrophobic and hydrophilic regions.

Anchored membrane protein

A membrane protein covalently attached to lipids that insert into the bilayer but do not span it.

Peripheral membrane protein

A protein associated with the membrane surface or with integral proteins, not embedded in the bilayer.

Transmembrane protein

An integral membrane protein that extends across the lipid bilayer, protruding on both sides.

Glycoprotein

A membrane protein with carbohydrate groups attached, involved in cell recognition and signaling.

Glycolipid

A lipid with attached carbohydrate residues on the membrane exterior, contributing to cell recognition.

Cholesterol

A sterol that modulates membrane fluidity by interacting with phospholipid tails; abundant in animal membranes.

Phytosterol

Plant equivalents of cholesterol that modulate membrane fluidity similarly to cholesterol.

Membrane fluidity

The ease with which lipids and proteins move laterally within the membrane, influenced by lipid composition and temperature.

Rafts (lipid rafts)

Membrane microdomains with distinct lipid composition that can concentrate certain proteins and influence signaling.

Aquaporin

A channel protein that greatly increases membrane permeability to water.

Simple diffusion

Diffusion of small, nonpolar, or uncharged molecules directly through the lipid bilayer without transport proteins.

Facilitated diffusion

Diffusion of molecules down their concentration gradient aided by membrane transport proteins (channels or carriers) without energy input.

Channel protein

A pore-forming protein that provides a passageway for specific ions or molecules across the membrane.

Carrier protein

A protein that binds specific solutes and changes shape to shuttle them across the membrane; can become saturated.

Osmosis

Movement of water across a membrane from areas of lower solute concentration to higher solute concentration.

Osmolarity

Total concentration of all dissolved solute particles in a solution per liter of water.

Osmotic pressure

The pressure required to prevent osmosis; proportional to osmolarity.

Tonicity

Effect of solute concentration on water movement across a membrane, distinguishing isotonic, hypotonic, and hypertonic solutions.

Isotonic

Two solutions with equal osmolarity across a membrane; no net water movement if the membrane is impermeable to solutes.

Hypotonic

External solution with lower solute concentration; water enters cell, potentially causing swelling.

Hypertonic

External solution with higher solute concentration; water exits cell, causing shrinkage.

Sodium–potassium pump (Na+/K+ pump)

Primary active transport protein that uses ATP to move Na+ out and K+ in, creating gradients.

Primary active transport

Transport that uses direct energy (e.g., ATP hydrolysis) to move solutes against their gradient.

Secondary active transport

Transport that uses energy stored in an established gradient (often Na+) to move another solute against its gradient.

Sodium–glucose co-transporter (SGLT)

A secondary active transporter that uses Na+ diffusion down its gradient to drive glucose uptake against its gradient.

Endocytosis

Process by which cells take in large molecules or particles via membrane invagination and vesicle formation.

Exocytosis

Process by which vesicles fuse with the plasma membrane to release contents to the extracellular space.

Phagocytosis

Endocytosis of large particles or cells, often mediated by receptors; forms a phagosome.

Pinocytosis

Endocytosis of fluids and dissolved substances; cellular “drinking” that is usually nonspecific.

Receptor-mediated endocytosis

Endocytosis initiated by specific receptor–ligand binding and clathrin-coated pits, highly selective.

Clathrin-coated pit

Membrane region coated with clathrin that forms vesicles during receptor-mediated endocytosis.

LDL receptor

Receptor that binds low-density lipoprotein for receptor-mediated endocytosis; defects cause familial hypercholesterolemia.

Endomembrane system

Interconnected network of membranes (nuclear envelope, ER, Golgi, lysosomes, vesicles) that traffic lipids and proteins within the cell.

Rough endoplasmic reticulum (RER)

ER studded with ribosomes; site of synthesis and modification of proteins destined for secretion or organelles.

Smooth endoplasmic reticulum (SER)

ER lacking ribosomes; lipid synthesis, detoxification, and Ca2+ storage.

Golgi apparatus

Stack of cisternae that processes, modifies, and ships proteins to their destinations; has cis and trans faces.

Lysosome

Digestive organelle containing hydrolytic enzymes for breaking down macromolecules; site of autophagy.

Autophagy

Cellular self-digestion of old organelles and components via lysosomes for recycling.

Mitochondrion

Organelle that generates ATP through cellular respiration; has double membrane, cristae, matrix, own DNA and ribosomes.

Chloroplast

Plant plastid performing photosynthesis; contains thylakoids, stroma, own DNA and ribosomes.

Plastid

Plant cell organelle family including chloroplasts and other storage/pigment entities.

Vacuole

Membrane-bound storage organelle; large central vacuole in plants maintains turgor pressure.

Peroxisome

Organelle that detoxifies peroxides and other toxic compounds; contains catalase.

Extracellular matrix (ECM)

Network outside cells comprising collagen, proteoglycans, and linking proteins; supports tissue structure and signaling; connects to the cytoskeleton via integrins.

Collagen

Primary structural protein of ECM providing tensile strength; abundant in connective tissues.

Integrin

Transmembrane receptor that links ECM to the cytoskeleton and participates in signaling and adhesion.

Cell wall

Rigid exterior layer in plants, fungi, and some bacteria; made of cellulose, chitin, or peptidoglycan; provides support and protection.

Desmosome

Junction that mechanically anchors adjacent animal cells, allowing some intercellular movement.

Tight junction

Junction that seals spaces between epithelial cells to prevent paracellular movement.

Gap junction

Channel-forming junction allowing direct cytoplasmic exchange of small molecules and ions between adjacent cells.

Plasmodesmata

Plant cell channels through cell walls that connect adjacent cells for transport and signaling.

Nucleus

Membrane-bound organelle containing most DNA; site of transcription; contains nucleolus and chromatin.

Chromatin

DNA-protein complex in the nucleus; condenses to form chromosomes during division.

Nucleolus

Nuclear subdomain where ribosomal RNA is synthesized and ribosome assembly begins.

Endoplasmic reticulum (ER)

Network of membranous tubules and sacs; site of protein and lipid synthesis; integrated with the Golgi and lysosomes through vesicles.

Chromosome

Discrete unit of DNA-protein complex carrying genetic information; becomes visible as chromosomes during cell division.

Cytoskeleton

Network of protein filaments (microfilaments, intermediate filaments, microtubules) supporting cell shape, organelle position, and transport.