Membrane Transport System PDF

Transport Across the Cell Membrane Membrane Transport Systems I. Passive Transport II. Active Transport III. Vesicular (Bulk) Transport  Cell membrane is the boundary between inside & outside… – separates cell from its environment Can it be an impenetr...

Transport Across the Cell Membrane Membrane Transport Systems I. Passive Transport II. Active Transport III. Vesicular (Bulk) Transport  Cell membrane is the boundary between inside & outside… – separates cell from its environment Can it be an impenetrable boundary? NO! IN OUT food OUT waste carbohydrates ammonia sugars, proteins salts amino acids CO2 IN lipids H2O salts, O2, H2O products cell needs materials in & products or waste out  TYPES OF CELLULAR TRANSPORT Weeee!!! Passive Transport cell doesn’t use energy high 1. Diffusion 2. Facilitated Diffusion low 3. Osmosis Active Transport This is cell uses energy gonna be hard - Protein Pumps high work!! Vesicular (Bulk) Transport cell uses energy low 1. Endocytosis 2. Exocytosis PASSIVE TRANSPORT cell uses no energy molecules move randomly Molecules spread out from an area of high concentration to an area of low concentration. (HighLow)  3 TYPES OF PASSIVE TRANSPORT SIMPLE DIFFUSION FACILITATED DIFFUSION – Diffusion with the help of channel proteins and carrier proteins OSMOSIS – Diffusion of water  Simple Diffusion random movement of molecules from an area of high concentration to an area of low concentration. (High to Low) Factors that Influence Diffusion Rates Distance – The shorter the distance, the faster molecules diffuse Molecular Size – Ions and small molecules diffuse more rapidly Temperature - – Diffusion is faster at high temperature Steepness of concentrated gradient - – The larger the gradient, the faster diffusion proceeds Membrane surface area - – The larger the area, the faster diffusion proceed Diffusion through phospholipid bilayer What molecules can get through directly? – fats & other lipids lipid  What molecules can NOT inside cell get through directly? NH3 salt  polar molecules  H2O  ions  salts, ammonia  large molecules sugar aa H2O  starches, proteins outside cell  Facilitated Diffusion A B diffusion of molecules from high to low using concentration transport proteins found in the cell Facilitated Diffusion membrane diffusion (Lipid - Transports larger or (Channel Bilayer) charged molecules Protein) - 2 kinds: - Channel proteins - Carrier proteins Carrier Protein  Facilitated Diffusion Glucose molecules Cellular Transport from a High High Concentration Cell Membrane Protein Low Concentration Channel channel Proteins Low Transport Through a  Go to Protein Section:  Channels through cell membrane – specific channels allow specific material across cell membrane inside cell H2O aa sugar NH3 salt outside cell Diffusion Through the Plasma Membrane Figure 3.7  Osmosis diffusion of water through a selectively permeable membrane Water moves from high to low concentrations Water moves freely through pores. Solute (green) too large to move across. ECF ICF  Concentration of water Direction of osmosis is determined by comparing total solute concentrations – Hypertonic solution - more solute, less water – Hypotonic solution - less solute, more water – Isotonic solution - equal solute, equal water water hypotonic hypertonic net movement of water  Managing water balance Cell survival depends on balancing water uptake & loss freshwater balanced saltwater  Active Transport cell uses energy (ATP) low molecules transported by carrier proteins molecules move from an area of low to an area of high concentration high ATP (Low  High)  Active Transport: Protein Pumps carrier proteins that require energy ATP to do work protein changes shape to move molecules: this requires energy! Active Transport: Protein Pumps Example: Sodium / Potassium ATP Pumps hydrolysis important in phosphorylation nerve responses. dephosphorylation  Types of active transport Primary active transport – also called direct active transport – directly uses ATP to transport molecules across a membrane  Types of active transport Secondary active transport (coupled transport or co-transport) – no direct use of ATP – uses the movement of one solute from high to low concentration to move another molecule from low concentration to high concentration (against its concentration gradient) Cotransporters can be classified as: symporters (Symport) – both molecules are transported in the same direction. antiporters (Antiport) – two ion or solutes are pumped in opposite directions across a membrane  Vesicular (bulk) Transport Moving large molecules into & out of cell – through vesicles & vacuoles 2 kinds – Endocytosis: materials are taken inside the cell phagocytosis = “cellular eating” pinocytosis = “cellular drinking” – Exocytosis: materials are secreted outside the cell  Endocytosis fuse with lysosome phagocytosis for digestion ATP pinocytosis non-specific process Exocytosis ATP Transport summary simple diffusion Lipids, hydrophobic molecules facilitated diffusion Ions, hydrophilic and Large molecules active ATP transport Ions, hydrophilic molecules