The Plasma Membrane & Cell Transport

Vocabulary flashcards covering key terms from the lecture notes on the plasma membrane and cell transport.

Plasma Membrane

The boundary of the cell, also called the cell membrane; a selectively permeable barrier surrounding the cell.

Selectively Permeable

Property of the plasma membrane that allows some substances to pass while restricting others.

Phospholipid Bilayer

Two-layer arrangement of phospholipids forming the membrane's core, contributing to selective permeability.

Phospholipid Head

Polar, hydrophilic region of a phospholipid that faces water.

Phospholipid Tail

Nonpolar, hydrophobic region of a phospholipid that avoids water.

Hydrophilic

Water-loving; describes the phospholipid heads.

Hydrophobic

Water-fearing; describes the phospholipid tails.

Peripheral Protein

Proteins attached to the interior or exterior surface of the membrane; involved in cell and hormone recognition.

Integral Protein

Proteins that span the membrane; form channels or carriers to move substances.

Channel Protein

Integral protein that forms a pore for specific ions or molecules to pass.

Carrier Protein

Integral protein that binds a substance and changes shape to shuttle it across the membrane.

Glycoprotein

Protein with attached carbohydrate chains; used for cell identification and adhesion.

Glycolipid

Lipid with attached carbohydrate; used in cellular signaling.

Extracellular Matrix (ECM)

Fibers and glycoproteins outside the cell forming the structural network of tissues.

Extracellular Fluid

The fluid outside the cell.

Cholesterol

Sterol within the membrane that modulates fluidity and stability.

Diffusion

Movement of molecules from high to low concentration along the concentration gradient; no energy required.

Concentration Gradient

Difference in the concentration of a substance across space.

Facilitated Diffusion

Diffusion that requires membrane proteins (channel or carrier) to move substances that cannot cross the bilayer directly.

Osmosis

Movement of water across a membrane from higher to lower water concentration; still along the gradient.

Hypotonic

Solution with lower solute concentration outside the cell; water tends to enter the cell.

Hypertonic

Solution with higher solute concentration outside the cell; water tends to leave the cell.

Isotonic

Solute concentrations inside and outside the cell are equal; water moves in and out at equal rates.

Turgor Pressure

Pressure exerted by water inside plant cells; helps maintain rigidity.

Plasmolysis

Plant cells shrink away from the cell wall in hypertonic solutions.

Cytolysis

Cell bursting due to swelling in hypotonic solutions.

Active Transport

Movement of substances against their concentration gradient; requires energy (ATP).

Sodium-Potassium Pump

Cell membrane pump that exports 3 Na+ and imports 2 K+ to maintain gradients.

Exocytosis

Movement of substances out of the cell via vesicles that fuse with the plasma membrane.

Phagocytosis

Endocytosis of large particles; 'cell eating'.

Pinocytosis

Endocytosis of fluids; 'cell drinking'.

Receptor-Mediated Endocytosis

Endocytosis initiated by receptor signals, often involving glycolipids for signaling.