Chapter 7 Membrane Structure & Function

Fluid Mosaic Model

A model that describes the plasma membrane structure as a mosaic of diverse protein molecules drifting within a fluid phospholipid bilayer.

Phospholipid Bilayer

A flexible double-layered sheet that makes up the cell membrane and forms a barrier between the cell and its surroundings.

Transmembrane Proteins

Integral proteins that span the entirety of the cell membrane to provide passage for molecules.

Peripheral Membrane Proteins

Proteins that are loosely bound to the surface of the membrane, providing shape and structure.

Aquaporins

Channel proteins that facilitate the transport of water across the membrane.

Osmosis

The movement of water molecules across a selectively permeable membrane from an area of lower solute concentration to an area of higher solute concentration.

Hypertonic Solution

A solution that has a higher solute concentration than another solution, causing cells to lose water.

Hypotonic Solution

A solution that has a lower solute concentration than another solution, causing cells to gain water.

Isotonic Solution

A solution where the concentration of solutes is equal inside and outside of the cell, resulting in no net movement of water.

Active Transport

The movement of substances against a concentration gradient, requiring energy in the form of ATP.

Sodium-Potassium Pump

An active transport mechanism that moves 3 sodium ions out of the cell and 2 potassium ions into the cell against their concentration gradients.

Endocytosis

The process by which a cell takes in materials through the formation of vesicles.

Exocytosis

The process by which materials are expelled from the cell inside vesicles that fuse with the plasma membrane.

Phagocytosis

Type of endocytosis where cells engulf large particles or cells, using vesicles.

Pinocytosis

Type of endocytosis where the cell engulfs extracellular fluid and its dissolved solutes.

Receptor-Mediated Endocytosis

A process where specific molecules are taken into the cell after binding to receptors on the cell surface.

Channel Proteins

Proteins that create hydrophilic tunnels in the membrane, allowing specific ions or molecules to pass through.

Carrier Proteins

Proteins that bind specifically to molecules they assist in transporting across the membrane.

Glycoprotein

A protein with carbohydrate chains attached that play a role in cell recognition and signaling.

Glycolipid

A lipid with a carbohydrate attached, found on the extracellular surface of cell membranes and contributing to cell recognition.

Cholesterol

A steroid molecule present in cell membranes that helps to maintain fluidity.

Diffusion

The passive movement of molecules from an area of high concentration to an area of low concentration.

Facilitated Diffusion

The process in which molecules pass through the membrane via the aid of membrane proteins, without the need for energy.

Concentration Gradient

A difference in the concentration of a substance across a space, leading to movement from high to low concentration.