MLB UNIT 2

Amphipathic Molecule

A molecule that has both hydrophilic (water-attracting) and hydrophobic (water-repelling) parts, such as fatty acids.

Phospholipid Bilayer

A double layer of phospholipids that create a semi-permeable membrane in cells, with hydrophilic heads facing outward and hydrophobic tails facing inward.

Fluid Mosaic Model

A model describing the structure of cell membranes, where lipids and proteins move fluidly within the layer, resembling a mosaic.

Selective Permeability

The ability of biological membranes to allow certain substances to pass while restricting others.

Diffusion

The net movement of molecules from a region of higher concentration to a region of lower concentration until equilibrium is achieved.

Osmosis

The movement of water molecules through a semi-permeable membrane from an area of lower solute concentration to an area of higher solute concentration.

Tonicity

A term describing the relative concentration of solutes in solutions that determines the direction and extent of osmotic movement.

Carrier Proteins

Membrane proteins that bind to specific substances and facilitate their transport across the membrane.

Channel Proteins

Integral proteins that form channels through which specific substances can pass through the membrane.

Active Transport

The process of moving molecules against their concentration gradient, requiring energy, usually from ATP.

Endocytosis

The process by which substances are brought into the cell by engulfing them in a vesicle formed from the cell membrane.

Exocytosis

The process of vesicles fusing with the cell membrane to release their contents outside the cell.

Integral Membrane Proteins

Proteins that are partially or fully embedded in the phospholipid bilayer and can serve various functions, including transport.

Fluidity of Membranes

The ability of membrane components to move laterally within the bilayer, affecting membrane function and integrity.

Cholesterol

A type of lipid that is found in animal cell membranes, which helps to maintain membrane fluidity and stability.

Glycoproteins

Proteins that have carbohydrate groups attached, playing key roles in cell recognition and adhesion.

Homotypic Adhesion

Cell adhesion between similar cells due to interactions of the same molecules on their surfaces.

Heterotypic Adhesion

Cell adhesion that occurs between different types of cells due to interaction of different molecules on their surfaces.

Gap Junctions

Channels that allow direct communication between adjacent cells, facilitating the transfer of small molecules and ions.

Desmosomes

Cell junctions that provide mechanical stability by linking adjacent cells together.

Tight Junctions

Junctions that prevent leakage of materials between adjacent cells, maintaining distinct cell membrane domains.

Aquaporins

Channel proteins that facilitate the passage of water across the cell membrane.

Na+/K+ Pump

An antiporter protein that moves sodium out of and potassium into the cell, crucial for maintaining membrane potential.