The Plasma Membrane Biology exam revision

Flashcards about the plasma membrane and transport mechanisms.

Plasma Membrane

Forms the boundary between the intracellular and extracellular environment, regulating temperature, pH, CO2, O2, and nitrogenous wastes.

Semi-permeable Membrane

A membrane that controls the movement of substances into and out of the cell.

Fluid-Mosaic Model

Model describing the plasma membrane as a double layer of lipids that flow and change shape, with specialized protein molecules embedded within.

Glycoprotein

Protein with carbohydrate attached

Glycolipid

Lipid with carbohydrate attached

Phospholipid Bilayer

Double layer of phospholipid molecules forming the basic structure of the plasma membrane.

Peripheral Membrane Protein

Protein associated with the plasma membrane that does not penetrate the hydrophobic core of the lipid bilayer.

Integral Membrane Protein

A protein that spans the phospholipid bilayer of a cell.

Cholesterol

Fatty molecule that adds stability to the plasma membrane without affecting fluidity.

Phospholipid Structure

Hydrophilic head and hydrophobic tails.

Cholesterol's Role

Fatty molecule that adds stability to the plasma membrane without affecting fluidity.

Integral Proteins

Permanent proteins; transmembrane proteins span both phospholipid layers.

Peripheral Proteins

Temporary proteins that cannot penetrate into the center of the phospholipid bilayer.

Adhesion Proteins

Proteins that link cells together; glycoproteins/carbohydrates play a role.

Transport Proteins

Passageways that allow substances to move across the membrane (includes carrier and channel proteins).

Receptor Proteins

Bind hormones and other substances that change a cell’s activities.

Recognition Proteins

Markers or antigens that allow the body to distinguish between its own cells and foreign cells (glycoproteins/carbohydrates play a role).

Passive Transport

Movement that does NOT require energy; includes diffusion and osmosis.

Diffusion

Net movement of particles from a region of high particle concentration to a region of lower particle concentration.

Concentration Gradient

The difference in particle concentration between two areas.

Facilitated Diffusion

Protein carriers or protein channels are involved to enable diffusion.

Osmosis

Diffusion of water across a selectively permeable membrane from an area of high water concentration to an area of low water concentration.

Osmotic Potential/Osmotic Pressure

The tendency of water to move into high solute environments.

Isotonic

Fluids inside and outside of a cell are of equal concentration.

Hypotonic

Cells surrounded by a solution with a lower solute concentration (higher water conc) than the cytoplasm; water will diffuse INTO the cell.

Hypertonic

Cells surrounded by a solution with a higher solute concentration (lower water conc) than the cytoplasm; water will diffuse OUT of the cell.

Transport Using Energy

Movement of substances across a membrane requiring energy.

Active Transport

Movement AGAINST the concentration gradient from areas of low solute concentration to areas of high solute concentration; requires ATP.

Bulk Transport

Movement of LARGE molecules across membranes; includes endocytosis and exocytosis; requires energy.

Endocytosis

Movement of a substance INTO the cell by fusing the membranes of the cell and the substance; requires energy.

Phagocytosis

Engulfs solid particles.

Pinocytosis

Engulfs liquid particles.

Exocytosis

Large molecules held in vesicles within the cell are transported to the external environment; requires energy.