2.2 Passive and Active Transport

Movement of materials across a cell membrane from a region of higher concentration to a region of lower concentration without energy input.
Concentration will equalize until the concentration is uniform on both sides.

Diffusion: Net movement of ions or molecules from high to low concentration across a semi-permeable membrane.
Facilitated Diffusion: Utilizes integral proteins to aid the passage of specific molecules along their concentration gradient.
Osmosis: Diffusion of water across a semi-permeable membrane.

States that particles constituting matter are in constant random motion, colliding and spreading out.
Molecular collisions facilitate diffusion.

Molecule Size: Smaller molecules diffuse faster.
Molecule Polarity: Non-polar substances pass more easily through membranes.
Molecule Charge: Charged ions may require transport proteins.
Concentration: Greater differences promote faster diffusion.
Temperature: Higher temperatures increase molecular motion.
Pressure: Increased pressure can enhance diffusion.
Equilibrium: Achieved when concentrations are equal, although molecules still move without net movement.

Channel Proteins: Allow movement based on size and charge (e.g., K+ transport).
Carrier Proteins: Bind specific molecules, change shape, and release them across the membrane.

Defined as the diffusion of water from a region of high water concentration to a region of low water concentration through a semi-permeable membrane.
Depends on solute concentration of particles on either side.

Isotonic: Equal concentration inside and outside the cell, balanced water movement.
Hypotonic: Lower solute concentration outside the cell; net water movement into the cell.
Hypertonic: Higher solute concentration outside the cell; net water movement out of the cell.

Animal Cells: In isotonic solutions, no net water movement; in hypotonic, cells may burst; in hypertonic, cells shrivel.
Plant Cells: In isotonic, no net water movement; in hypotonic, cells become turgid; in hypertonic, cells undergo plasmolysis and the cytoplasm shrinks.

Passive transport does not require energy; materials move from high to low concentration.

Defined as the movement of materials against a concentration gradient from low to high concentration, requiring cellular energy (ATP).

Utilizes ATP to move ions across a membrane against their gradient (e.g., Na+/K+ pump).
Involves transport proteins for ion movement.

Uses an electrochemical gradient to move ions across a membrane.
Example: H+/sucrose pump where H+ ion concentration drives sucrose entry into the cell.

Endocytosis: Cell engulfs material by folding the membrane and forming a vesicle.
- Phagocytosis: Engulfing large particles.
- Pinocytosis: Engulfing liquids and small particles.
- Receptor-Mediated Endocytosis: Specific molecules bind to receptors, and the membrane folds inward to form a vesicle.

A transport method where a vesicle fuses with the cell membrane to release its contents outside the cell.