- Cell Walls
- The Plasma Membrane
- The fluid mosaic model describes the structure of the plasma membrane.
- The fluid portion of membranes is produced by a double layer of phospholipids: the phospholipid bilayer.
- A variety of proteins in the cell membrane form a protein mosaic.
- Transport across Membranes
- Molecules in fluids move in response to gradients.
- Movement across membranes occurs by both passive and energy-requiring transport.
- Passive Transport: Movement down Concentration Gradients
- Molecules diffuse from areas of high concentration to areas of low concentration.
- Molecules diffuse across membranes down their concentration gradients.
- Osmosis is the diffusion of water across membranes.
- Osmosis across the cell membrane plays an important role in the lives of cells.
- Energy-Requiring Transport across Membranes
- Active transport uses energy to move molecules across membranes.
- Cells engulf particles or fluids by endocytosis.
- Transport across Intracellular Membranes
- Vacuoles help regulate cell volume.
- Cell Connections and Communication
- Desmosomes attach cells together.
- Tight junctions leakproof the cell.
- Gap junctions and plasmodesmata allow communications between cells.
- The fluid mosaic model describes the structure of the plasma membrane.
Designed in cooperation with
Andrew Stull and Steven Brunasso.
Last Update - July 25, 1997
