Structure and Function of Plasma Membranes

Phospholipids

Main fabric of cell membranes, amphipathic molecules.

Hydrophilic Head

Polar part of phospholipid, attracts water.

Hydrophobic Tails

Nonpolar fatty acid chains, repel water.

Saturated Fatty Acids

Carbons fully bonded to hydrogen, no double bonds.

Unsaturated Fatty Acids

At least one double bond between carbons.

Phospholipid Bilayer

Arrangement with heads outward, tails inward.

Fluid Mosaic Model

Membrane structure with diverse components, fluid nature.

Integral Proteins

Proteins embedded within the phospholipid bilayer.

Transmembrane Proteins

Integral proteins spanning the entire membrane.

Peripheral Proteins

Proteins located on membrane surfaces only.

Glycoproteins

Carbohydrates attached to proteins for recognition.

Glycolipids

Carbohydrates attached to lipids, aiding cell recognition.

Membrane Fluidity

Flexibility of membrane, influenced by temperature and composition.

Cholesterol

Regulates membrane fluidity, stabilizes structure.

Cell-Cell Recognition

Function of carbohydrates in identifying cells.

Membrane Asymmetry

Different inner and outer membrane surfaces.

Passive Transport

Movement across membrane without energy input.

Active Transport

Energy-requiring movement against concentration gradient.

Bulk Transport

Transport of large molecules via vesicles.

Cellular Responses

Reactions initiated by external signals received by membranes.

Adhesion

Binding of cells to neighboring cells.

Membrane Functions

Regulates entry/exit, signal reception, and adhesion.

Fluid Mosaic Model

Describes cell membrane structure as dynamic and flexible.

Phospholipid Bilayer

Basic structure of cell membranes, hydrophilic heads, hydrophobic tails.

Membrane Proteins

Proteins embedded in membranes, serve various functions.

Glycoproteins

Proteins with carbohydrates, aid in cell recognition.

Passive Transport

Movement of substances without energy input.

Diffusion

Movement from high to low concentration.

Osmosis

Diffusion of water across a selectively permeable membrane.

Tonicity

Relative concentration of solutes in solutions.

Permeant Molecules

Molecules that can cross the phospholipid bilayer.

Concentration Gradient

Difference in concentration across a membrane.

Facilitated Diffusion

Passive transport using membrane proteins for assistance.

Channel Proteins

Proteins that form pores for ion/polar molecule passage.

Carrier Proteins

Proteins that bind and transport specific substances.

Equilibrium

State where concentrations are equal across a membrane.

Hydrophobic Molecules

Nonpolar molecules that easily pass through membranes.

Small Polar Molecules

Molecules like water that can cross membranes.

Large Polar Molecules

Molecules like glucose that cannot pass through membranes.

Ions

Charged particles that cannot cross membranes freely.

Factors Affecting Diffusion

Concentration, mass, temperature, surface area, pressure.

Active Transport

Movement of substances requiring energy input.

Selectively Permeable

Property of membranes allowing selective molecule passage.

Extracellular Matrix

Network outside cells providing structural and biochemical support.

Concentration Gradient

Difference in solute concentration across a membrane.

GLUTS

Glucose transport proteins facilitating glucose movement.

Tonicity

Relative concentration of solute and water across membranes.

Hypertonic Solution

Lower solute concentration than cytosol; water exits cell.

Isotonic Solution

Equal solute concentration to cytosol; no net water movement.

Hypotonic Solution

Higher solute concentration than cytosol; water enters cell.

Extracellular Fluid

Fluid outside cells affecting cell volume via osmosis.

Turgor Pressure

Pressure from plasma membrane against cell wall in plants.

Plasmolysis

Detachment of plasma membrane from cell wall in hypertonic solutions.

In Vivo

Processes occurring in a living organism.

In Vitro

Experiments conducted outside a living organism.

Contractile Vacuoles

Organelles in protists that expel excess water.

Osmoregulation

Regulation of water and solute balance in organisms.

Solute

Substance dissolved in a solvent, affecting concentration.

Selectively Permeable Membrane

Membrane allowing certain substances to pass through.

Water Concentration

Amount of water in a solution, influencing osmosis.

Cytosol

Liquid component of the cytoplasm where cellular processes occur.

Net Movement of Water

Overall direction of water movement across a membrane.

Marine Invertebrates

Organisms matching internal salt concentration to environment.

Freshwater Protists

Organisms using vacuoles to manage water influx.

Cell Wall

Rigid outer layer in plant cells providing structure.

Passive Transport

Movement across membranes without energy use.

Osmosis

Diffusion of water across a semipermeable membrane.

Diffusion

Movement of molecules from high to low concentration.

Active Transport

Movement against concentration gradient requiring energy.

Electrochemical Gradient

Combined concentration and electrical gradients affecting ions.

Primary Active Transport

Uses ATP to move substances against gradients.

Secondary Active Transport

Uses existing gradients to move different substances.

Uniporter

Transports one molecule or ion across a membrane.

Symporter

Transports two different molecules in the same direction.

Antiporter

Transports two different molecules in opposite directions.

Na+-K+ Pump

Moves 3 Na+ out and 2 K+ in using ATP.

Electrogenic Pump

Creates a charge difference across the membrane.

Endocytosis

Process of importing large molecules into cells.

Exocytosis

Process of exporting substances from cells.

Phagocytosis

Cellular eating; engulfs large particles.

Pinocytosis

Cellular drinking; engulfs small volumes of fluid.

Receptor-Mediated Endocytosis

Targets specific substances via receptor binding.

Carrier Proteins

Integral proteins facilitating transport across membranes.

Vesicles

Membrane-bound sacs transporting materials in cells.

Hydrolysis of ATP

Process releasing energy for active transport.

Integral Membrane Proteins

Proteins embedded in cell membranes for transport.