Cell Membrane Structure and Transport Mechanisms

Phospholipid Bilayer

Double layer of phospholipids forming cell membrane.

Hydrophobic Region

Nonpolar tails of phospholipids, repel water.

Hydrophilic Region

Polar heads of phospholipids, attract water.

Simple Diffusion

Movement of small nonpolar molecules across membrane.

Facilitated Diffusion

Transport of large polar molecules via protein channels.

Active Transport

Energy-requiring movement against concentration gradient.

Cholesterol Role

Maintains membrane fluidity across temperature changes.

Fluid Mosaic Model

Describes membrane structure as dynamic and varied.

Selective Permeability

Allows specific substances to enter or exit cell.

Osmosis

Diffusion of water across a selectively permeable membrane.

Hypotonic Solution

Lower solute concentration, causes cell swelling.

Isotonic Solution

Equal solute concentration, no net water movement.

Hypertonic Solution

Higher solute concentration, causes cell shrinking.

Endocytosis

Process of engulfing substances into the cell.

Exocytosis

Process of expelling substances from the cell.

Protein Channels

Facilitate transport of specific molecules across membrane.

Turgor Pressure

Pressure from water in plant cells, maintains structure.

Nutrient Absorption

Active transport of nutrients from soil into roots.

Glucose Transport

Can be passive or active depending on conditions.

Energy Requirements

Active transport uses energy; passive does not.

Homeostasis Maintenance

Osmosis and diffusion regulate cell internal environment.