AP Bio Chapter 7

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Selective Permeability

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

Amphipathic

Describes a molecule with both hydrophilic and hydrophobic regions.

Fluid Mosaic Model

Describes the cell membrane as a flexible layer with proteins embedded in or attached to a fluid lipid bilayer.

Integral Proteins

Proteins embedded within the lipid bilayer that often span the membrane.

Peripheral Proteins

Proteins attached to the surface of the membrane, not embedded in the lipid bilayer.

Glycolipids

Lipids with carbohydrate chains attached that are involved in cell recognition.

Glycoproteins

Proteins with carbohydrate chains attached that function in cell recognition and signaling.

Transport Proteins

Proteins that help move substances across the cell membrane.

Aquaporins

Channel proteins that specifically facilitate water movement across the membrane.

Diffusion

Movement of molecules from an area of higher concentration to an area of lower concentration.

Concentration Gradient

Difference in the concentration of a substance across a space or membrane.

Passive Transport

Movement of substances across a membrane without the use of cellular energy.

Osmosis

Diffusion of water across a selectively permeable membrane.

Tonicity

Ability of a surrounding solution to cause a cell to gain or lose water.

Isotonic

Solution with the same solute concentration as the cell; no net water movement.

Hypertonic

Solution with a higher solute concentration than the cell; water moves out of the cell.

Hypotonic

Solution with a lower solute concentration than the cell; water moves into the cell.

Osmoregulation

Control of water balance within a cell or organism.

Turgid

Firm condition of a plant cell when water enters by osmosis.

Flaccid

Soft or limp condition of a plant cell when water leaves the cell.

Plasmolysis

Shrinking of the cytoplasm and membrane away from the cell wall due to water loss.

Facilitated Diffusion

Passive transport of molecules across a membrane through transport proteins.

Ion Channels

Proteins that allow specific ions to move across the membrane.

Gated Channels

Ion channels that open or close in response to a stimulus.

Active Transport

Movement of substances across a membrane using energy, usually ATP.

Sodium Potassium Pump

Transport protein that moves sodium ions out of the cell and potassium ions into the cell using ATP.

Membrane Potential

Voltage difference across a cell membrane caused by the distribution of ions.

Electrochemical Gradient

Combined effect of concentration gradient and electrical charge on ion movement.

Electrogenic Pump

Transport protein that generates voltage across a membrane while moving ions.

Proton Pump

Transport protein that moves hydrogen ions across a membrane to build up a proton gradient.

Cotransport

Coupled transport where the movement of one substance drives the movement of another.

Exocytosis

Process of vesicles fusing with the cell membrane to release contents outside the cell.

Endocytosis

Process by which the cell takes in materials by forming vesicles from the plasma membrane.

Phagocytosis

Type of endocytosis in which the cell engulfs large particles or other cells.

Pinocytosis

Type of endocytosis that takes in fluids and dissolved solutes.

Receptor-mediated Endocytosis

Endocytosis process that uses specific receptors to capture target molecules.

Ligands

Molecules that bind specifically to receptors to trigger a cellular response.