Presentation on theme: "Membrane Transport. 3 Types of transport Passive Transport Simple diffusion –Small non-polar molecules No ions –Examples: Fatty acids Steroids CO 2 O."— Presentation transcript:
Mediated Transport Passive mediated transport –Facilitated diffusion Carrier proteins Channel proteins –DOWN a conc. gradient Active transport –Primary active transport—uses ATP –Secondary active transport—uses a different energy source –Pumps things UP a conc. gradient
How to tell mediated transport vs. simple diffusion Saturation kinetics Competition kinetics Specificity
The Pore-Forming Toxins Lethal molecules produced by many organisms Insert themselves into the host cell plasma membrane Kill by –collapsing ion gradients –facilitating entry by toxic agents –introducing a harmful catalytic activity
Colicins Produced by E. coli Inhibit growth of other bacteria (even other strains of E. coli) Single colicin molecule can kill a host!
Consequences of Na/K ATPase Two ion gradients –Used as energy source –Electrical signaling Charge difference across membrane –Membrane potential difference –Negative on inside -60 to –90 mV in animal cells ~ -150 mV in bacteria -200 to –300 mV in plants –Not just due to these ions Phosphatidylserine on inside of PM Other ions
Indirect (secondary) AT Na/glucose symporter –Intestinal absorptive cells