The Cell Membrane and Transport The membrane is

The Cell Membrane and Transport

The membrane is a fluid (able to move freely) mosaic (made of many different parts) with a double layer of phospholipids and embedded proteins throughout. Jobs: Regulates exchange Creates a barrier Communication Identification

Phospholipids have both hydrophilic and hydrophobic regions

The proteins form a mosaic pattern on the membrane. - Special Membrane Molecules Cholesterol - reinforces membrane by connecting phospholipids Glycolipids and Glycoproteins – used for cell to cell attachment and cell communication

Special Membrane Proteins 1. Channel Proteins - form small openings for large molecules to diffuse through 2. Carrier Proteins- binding site on protein surface that "grabs" certain molecules and pulls them into the cell (uses energy, but not always the cell’s energy) Gated Channels - carrier proteins that open/close

3. Receptor Proteins – communication enzyme that triggers a cell response when the correct signal attaches 4. Recognition Proteins - ID tags, identify cells to the immune system 5. Enzymatic Proteins – perform specific chemical reactions

Transport Across Membrane p in r o a qu A *Selectively permeable – only some things can cross What things can pass? What cannot pass?

Passive Transport No ATP Required

Passive Transport (no energy) Simple Diffusion - water, oxygen and other molecules move themselves from areas of high concentration to areas of low concentration (down a concentration gradient), no cell energy required

Facilitated Diffusion - diffusion through protein openings (channel or carrier proteins)

OSMOSIS Osmosis - diffusion of water specifically Water is always welcome to come into the cell. This also means that water is always able to go out. Balancing the amount of water in the cell is crucial to homeostasis. Osmosis affects the amount of water inside cells, and different solutions can draw water out of the cell (dehydrating it) or cause cell to absorb excess water (overhydrating) Simple rule of osmosis Hyper Sucks!

Isotonic solutions– same conc of water and solute in/out, no net movement of water Hypotonic solutions– less solute/more water outside cell, water moves into the cell, cell could burst Hypertonic solutions – more solute/less water outside cell, water moves out of the cell, cell shrinks

Osmosis in U Tubes

STOPPING OSMOSIS Contractile Vacuoles are found in freshwater microorganisms to pump out excess water in aquatic areas to counterbalance the hypotonic environment (freshwater only) Turgor pressure occurs in plants cells as their central vacuoles fill with water and puts pressure on the cell wall preventing more water from coming in.

Active Transport Requires ATP

Active Transport - moving molecules "uphill" against their concentration gradient (from low to high), requires cell energy (ATP) Endocytosis - taking substances into cell in vesicles (golgi); pinocytosis for water, phagocytosis for solids

Exocytosis – reverse of endocytosis to move stuff out of the cell, such as the removal of waste

Protein Pump – Any protein that uses ATP to actively transport a molecule against a concentration gradient - Ex: Sodium-Potassium Pump – protein that maintains a balance of Na+ and K+ for nervous system function. A huge amount of energy in our bodies is used to power this pump and prevent sodium from building up within our cells. Drives the communication of our nerves

SODIUM POTASSIUM PUMP