Cell Membrane

Cell Membrane

A dynamic structure that protects the cell and regulates the movement of substances in and out.

Fluid Mosaic Model

Describes the cell membrane as a flexible layer with various components that move laterally within the bilayer.

Phospholipid Bilayer

The fundamental structure of the cell membrane, consisting of hydrophilic heads and hydrophobic tails.

Hydrophilic Head

The water-attracting part of a phospholipid that faces outward towards water-based environments.

Hydrophobic Tails

The water-repelling parts of phospholipids that face inward, forming a semi-permeable barrier.

Protein Channels

Proteins embedded in the membrane that facilitate the passage of specific molecules through facilitated diffusion.

Cholesterol

Molecules that maintain membrane fluidity by preventing phospholipid fatty acid chains from sticking together.

Glycoproteins

Proteins with carbohydrate chains attached, involved in cell recognition and signaling.

Passive Transport

Movement of substances across the cell membrane without the use of energy.

Diffusion

The movement of molecules from an area of higher concentration to an area of lower concentration until equilibrium is reached.

Osmosis

The diffusion of water through a selectively permeable membrane from lower to higher solute concentration.

Active Transport

A process that requires energy to move substances against their concentration gradient.

Sodium-Potassium Pump

An example of active transport that moves sodium ions out and potassium ions into the cell.

Endocytosis

A form of active transport where the cell membrane engulfs large molecules or particles to bring them into the cell.

Pinocytosis

A type of endocytosis involving the uptake of fluids and dissolved substances, often called "cell drinking."

Phagocytosis

A specific type of endocytosis that engulfs large particles or whole cells, such as bacteria.

Concentration Gradient

The difference in concentration of a substance across a space, influencing the direction of movement.

Physical Nature

Refers to the size and polarity of substances affecting their ability to cross the membrane.

Chemical Nature

The properties of molecules that determine their interaction with the hydrophobic core of the phospholipid bilayer.

Surface Area to Volume Ratio

A relationship that limits cell size and affects the efficiency of material exchange; larger cells may divide or adapt to increase surface area.