Biology 2E Chapter 5: Structure and Function of Plasma Membranes

Vocabulary flashcards covering the structure of the plasma membrane, the fluid mosaic model, types of transport (passive, active, bulk), and osmoregulation based on Chapter 5.

Permeability Barrier

A function of the plasma membrane that prevents leakage and acts as a gateway for the transport of nutrients in and wastes out of the cell.

Protein Anchor

A function of the plasma membrane where it holds transport proteins in place and serves as the site for proteins participating in bioenergetics and chemotaxis.

Proton Motive Force (PMF)

An energy source generated and used at the site of the plasma membrane for energy conservation.

Fluid Mosaic Model

A model proposed in 1972 by S.J. Singer and G.L. Nicolson describing the membrane as a mosaic of phospholipids, cholesterol, proteins, and carbohydrates.

Integral membrane proteins

Proteins that are firmly embedded in the plasma membrane.

Peripheral membrane proteins

Proteins that have only one portion anchored in the membrane or occur only on the surfaces.

Phospholipid

An amphiphilic molecule composed of two fatty acid chains, a glycerol molecule, and a polar phosphate group.

Saturated fatty acid

A fatty acid where carbons are saturated with H and all C-C bonds are single bonds.

Unsaturated fatty acid

A fatty acid that contains at least one double $C=C$ bond.

Glycoproteins

Carbohydrates bound to proteins on the exterior surface of the plasma membrane, functioning in cell-cell recognition and attachment.

Glycolipids

Carbohydrates bound to lipids on the exterior surface of the plasma membrane, functioning in cell-cell recognition and attachment.

Cholesterol

A component located within the fatty acid layer that acts as a fluidity buffer, keeping membranes fluid when cold and preventing excess fluidity when hot.

Passive Transport

The simplest type of transport, such as diffusion, which requires no energy to move substances down their concentration gradient.

Flux

Defined as $\text{mass/area/time}$, it refers to the rate of movement of a substance across the membrane.

Facilitated Transport

Also known as facilitated diffusion, it moves substances down concentration gradients through transmembrane integral membrane proteins.

Channel Proteins

Transmembrane proteins with a hydrophilic core that attract ions or polar molecules; some are open constantly while others are gated.

Aquaporins

Specific channel proteins that allow for the transport of $H_2O$.

Carrier Proteins

Proteins specific to a single substance that bind to it, change shape, and carry it to the other side of the membrane, such as Glucose transport proteins (GLUTS).

Osmosis

The diffusion of water across a membrane from an area of higher water concentration to one of lower water concentration.

Tonicity

Describes how an extracellular solution can change the volume of a cell by affecting osmosis.

Osmolarity

The total solute concentration of a solution, including both permeable and non-permeable solutes.

Hypotonic

An extracellular fluid with lower osmolarity than the cytosol, causing water to enter the cell.

Isotonic

An extracellular fluid with the same osmolarity as the cytosol, resulting in no net movement of water.

Hypertonic

An extracellular fluid with higher osmolarity than the cytosol, causing water to leave the cell.

Plasmolysis

The detachment of the plasma membrane from the cell wall when a cell is placed in a hypertonic solution.

Contractile vacuole

A structure used by freshwater protists like paramecia to pump water out of their cells to prevent bursting.

Active Transport

The transport of ions or molecules through a membrane protein against a concentration or electrochemical gradient, requiring energy.

Primary Active Transport

A type of active transport where ATP provides the energy directly.

Secondary Active Transport

A type of active transport where an electrochemical gradient provides the energy to move a substance.

Uniporter

A carrier protein used in active transport that carries one molecule or ion.

Symporter

A carrier protein used in active transport that carries two different molecules or ions in the same direction.

Antiporter

A carrier protein used in active transport that carries two different molecules or ions in different directions.

Endocytosis

A type of bulk transport used to import molecules or particles that are too large to pass through a transport protein.

Phagocytosis

A type of endocytosis, or 'cellular eating', where the cell membrane surrounds and engulfs a large particle.

Pinocytosis

A type of endocytosis, or 'cellular drinking', where the cell membrane invaginates and surrounds a small volume of fluid.

Receptor-mediated endocytosis

A targeted type of endocytosis where specific substances bind to receptors on the external surface of the membrane before being taken up.

Exocytosis

A type of bulk transport where vesicles containing substances fuse with the plasma membrane to release contents to the exterior of the cell.