Cell membrane structure ch. 5

Phospholipids

Molecule that forms the bilayer of the cell's membrane, has a polar, hydrophilic head bonded to two nonpolar, hydrophobic tails.

Glycolipids

Lipid in the plasma membrane that contains an attached carbohydrate chain; assembled in Golgi apparatus.

Glycoproteins

Protein in plasma membrane that contains an attached carbohydrate chain; assembled in Golgi apparatus.

Channel proteins

Proteins that form a channel to allow a particular molecule or ion to cross the plasma membrane.

Carrier proteins

Proteins in the plasma membrane that combines with and transports a molecule or an ion across the plasma membrane.

Cell recognition proteins

Glycoproteins in the plasma membrane that identify self and help the body defend itself against pathogens.

Receptor proteins

Proteins located in the plasma membrane or within the cell; bind to a substance that alters some metabolic aspect of the cell.

Enzymatic proteins

Protein that catalyzes a specific reaction; may be found in the plasma membrane or the cytoplasm of the cell.

Junction proteins

Protein in the cell membrane that assists in cell-to-cell communication.

Plasma membrane's crucial function

Selectively permeable.

Aquaporins

Channel protein through which water can diffuse across a membrane.

Bulk transport

Movement of substances, usually large particles, across the plasma membrane using vesicles.

Diffusion

Movement of molecules or ions from a region of higher to lower concentration.

Solution

A homogeneous mixture composed of two or more substances, where one is dissolved in another.

Solute

The substance that is dissolved in a solution; present in a smaller amount.

Solvent

The substance that dissolves the solute; present in a larger amount (e.g., water in a sugar solution).

Osmosis

The movement of water molecules through a semipermeable membrane from a region of lower solute concentration to higher solute concentration.

Osmotic pressure

The pressure required to prevent the flow of water across a semipermeable membrane due to osmosis.

Isotonic solution

A solution with the same solute concentration as another solution, resulting in no net movement of water across a membrane.

Tonicity

The ability of a solution to cause a cell to gain or lose water, based on solute concentration relative to the cell.

Hypotonic solutions

A solution with a lower solute concentration than the cell, causing water to enter the cell and potentially swell.

Hemolysis

The bursting of red blood cells due to excessive water intake in a hypotonic solution.

Turgor pressure

The pressure exerted by water inside the cell against the cell wall, important for plant rigidity.

Hypertonic solutions

A solution with a higher solute concentration than the cell, causing water to leave the cell and shrink.

Crenation

The shrinkage of animal cells (especially red blood cells) when placed in a hypertonic solution.

Plasmolysis

The process in plant cells where the cell membrane pulls away from the cell wall due to water loss in a hypertonic solution.

Facilitated diffusion

Passive movement of molecules across a membrane through transport proteins; no energy required.

Active transport

Movement of molecules against their concentration gradient using energy (usually ATP).

Pumps (active transport proteins)

Membrane proteins that use energy to move ions or molecules across the membrane (e.g., sodium-potassium pump).

Exocytosis

Process where cells release substances by vesicles fusing with the plasma membrane.

Endocytosis

Process where cells take in substances by forming vesicles from the plasma membrane.

Phagocytosis

Type of endocytosis where a cell engulfs large particles or cells ("cell eating").

Pinocytosis

Type of endocytosis where a cell takes in fluids and dissolved substances ("cell drinking").

Receptor-mediated endocytosis

A selective form of endocytosis where receptors bind specific molecules before internalizing them.

Extracellular matrix (ECM)

Network of proteins and carbohydrates outside animal cells that provides structural support and helps with cell signaling.

Adhesion junctions

Cell junctions that anchor cells together and maintain tissue integrity.

Tight junctions

Cell junctions that seal neighboring cells to prevent leakage of materials between them.

Gap junctions

Channels between animal cells that allow direct communication and transfer of ions or molecules.

Cell wall

Rigid outer layer found in plant cells that provides structure and protection; made of cellulose.

Plasmodesmata

Channels through plant cell walls that connect the cytoplasm of adjacent cells, allowing transport and communication.