BIOL 101 – Membranes and Transport (Lecture Notes Review)

Vocabulary flashcards covering membrane structure, components, and transport mechanisms as presented in BIOL 101 lecture notes.

Extracellular matrix (ECM)

Animal cell–secreted glycoprotein-rich material surrounding the cell; collagen is common; integrins link ECM to the cytoskeleton and influence cell behavior.

Glycoprotein

A protein with carbohydrate groups attached; part of membranes/ECM and can serve as markers or receptors.

Glycolipid

A lipid with a carbohydrate group attached; contributes to membrane structure and tissue-specific cell marking.

Peripheral membrane protein

Protein bound to the membrane surface, not embedded in the hydrophobic core.

Integral membrane protein

Protein embedded in the lipid bilayer, often spanning the membrane and interacting with the hydrophobic interior.

Transmembrane protein

Integral protein that spans the entire lipid bilayer; can have one or more transmembrane domains.

Phospholipid bilayer

Two-layered structure of phospholipids with hydrophilic heads outward and hydrophobic tails inward, forming the cell membrane.

Fluid Mosaic Model

Membranes are a dynamic mosaic of lipids and proteins that move laterally within a fluid bilayer.

Cholesterol (in membranes)

Sterol that sits among phospholipids, modulating membrane fluidity and stability.

Sterols

Nonpolar lipids with a hydroxyl group (e.g., cholesterol) that help regulate membrane fluidity.

Membrane protein functions

Transport, enzymes, receptors, cell identity markers, adhesion, and attachment to the cytoskeleton.

Channel protein

A hydrophilic pore in the membrane that allows specific ions or polar molecules to cross; often gated.

Carrier protein

Membrane protein that binds a specific molecule and changes shape to move it across the membrane (facilitated diffusion or active transport).

Aquaporin

Water channel protein that facilitates osmosis across the membrane.

Diffusion

Passive movement of molecules from high to low concentration; no energy required.

Osmosis

Net diffusion of water across a semipermeable membrane toward higher solute concentration.

Hypertonic

Solution with higher solute concentration relative to another solution.

Hypotonic

Solution with lower solute concentration relative to another solution.

Isotonic

Solutions with equal solute concentration on both sides of a membrane.

Osmotic pressure

Force required to stop osmotic flow; relates to cell swelling or shrinking in different solutions.

Endocytosis

Active uptake of extracellular material by vesicle formation; requires energy.

Phagocytosis

Endocytosis of particulate matter (cell eating).

Pinocytosis

Endocytosis of fluid and dissolved solutes (cell drinking).

Receptor-mediated endocytosis

Selective uptake of specific molecules after binding to cell-surface receptors.

Exocytosis

Secretion or expulsion of materials from the cell via vesicle fusion with the plasma membrane; requires energy.

Na+/K+ pump (sodium–potassium pump)

Direct active transport that moves 3 Na+ out and 2 K+ in per ATP; maintains ion gradients.

Primary active transport

Active transport driven directly by ATP hydrolysis.

Secondary (coupled) active transport

Active transport powered indirectly by the energy released from diffusion of another substance (e.g., Na+ gradient).

Uniporter

Carrier that transports a single molecule at a time (facilitated diffusion or active transport).

Symporter

Carrier that moves two different molecules in the same direction across the membrane.,

Antiporter

Carrier that moves two different molecules in opposite directions across the membrane.

Plasmodesmata

Openings in plant cell walls that connect cytoplasm of adjacent cells, functioning like gap junctions.

Glycolipids as cell markers

Glycolipids on the membrane act as tissue-specific identity markers for cells.

MHC proteins

Major histocompatibility complex proteins that help immune cells recognize self vs nonself.

Adherens junctions, desmosomes, hemidesmosomes

Types of adhesive junctions that mechanically connect cells to each other or to the ECM.

Tight (septate) junctions

Connections that seal the space between adjacent plasma membranes to prevent leakage.

Gap junctions

Communicating junctions that allow direct chemical or electrical signaling between neighboring cells.

Endomembrane: Plasmodesmata

Plant cell openings in walls connecting cytoplasm of neighboring cells (analogous to gap junctions in animals).

Basic membrane structure

Phospholipid bilayer with hydrophilic heads and hydrophobic tails; embedded proteins and cholesterol.

Five components of cellular membranes

Phospholipid bilayer, sterols, integral membrane proteins, interior protein network, and cell-surface markers.

Transmembrane domain

Hydrophobic region of a protein that spans the lipid bilayer; often an α-helix.

β-barrel pore

Pore formed by a cylinder of β-sheets in a transmembrane protein, allowing polar molecules to pass.

Membrane fluidity determinants

Tail length, degree of unsaturation, temperature, and cholesterol content regulate fluidity.

Gel vs liquid-ordered vs liquid-disordered

Membrane phases describing lipid organization; transitions depend on temperature and lipid composition.

ER vs plasma membrane lipid composition

ER membranes are richer in unsaturated lipids and lower cholesterol; plasma membranes have mixed lipids and cholesterol, affecting fluidity and thickness.

Endocytosis vs exocytosis energy

Both processes require energy; endocytosis brings materials in, exocytosis releases materials out.