Membrane Structure and Transport: Fluid Mosaic Model, Passive & Active Processes

Phospholipids

Main structural component of membranes

Glycerol

Part of phospholipids, combined with 2 fatty acid tails and a phosphate group

Fatty Acid Tails

Hydrophobic part of phospholipids

Phosphate Group

Hydrophilic part of phospholipids

Amphipathic

Characteristic of phospholipids that allows them to form a bilayer

Phospholipid Bilayer

Structure formed by phospholipids in membranes

Van der Waals Forces

Forces that hold the phospholipid bilayer together

Membrane Proteins

Can be on one side or transmembrane, spanning across the membrane

Membrane Protein Functions

Includes transport, enzymes, signaling/communication, and structure

Carbohydrates

Polysaccharides attached to proteins (glycoproteins) or lipids (glycolipids) for cell identification

Fluid Mosaic Model

Describes the membrane as having components that can move laterally and emergent properties due to their arrangement

Passive Transport

Does not require metabolic energy (ATP) and includes simple diffusion, osmosis, and facilitated diffusion

Dynamic Equilibrium

State where there is no net movement at equilibrium

Diffusion

Tendency of molecules to fill available space due to random motion

Osmosis

Diffusion of water across a selectively permeable membrane

Solvent

A substance capable of dissolving other substances

Solute

A dissolved substance

Tonicity

Ability of a solution to cause a cell to gain or lose water

Isotonic Solution

Solute concentration outside = solute concentration inside, resulting in no net water movement

Hypertonic Solution

Solute concentration outside > solute concentration inside, causing the cell to lose water

Hypotonic Solution

Solute concentration inside > solute concentration outside, causing the cell to gain water

Facilitated Diffusion

Passive transport through a transport protein that does not require ATP

Active Transport

Requires ATP and moves substances against their concentration gradient

Sodium-Potassium Pump

Example of active transport through a carrier protein

Bulk Transport

Type of active transport that moves many molecules at once with vesicles

Exocytosis

Process where a vesicle fuses with the plasma membrane to release contents

Endocytosis

Process of materials being taken in by folding the plasma membrane inwards to form a vesicle

Phagocytosis

Type of endocytosis that involves large food particles

Pinocytosis

Type of endocytosis that involves fluids and dissolved molecules