nonmediated
Charged particles like Na and K ions move across membranes through transport proteins. I think the specific transport protein you're probably looking for is the Sodium-Potassium Pump, though it may be known under other names.
My gr 12 Biology teacher (I live in Canada, if gr 12 sounds strange to you) showed us this really awesome video, which can be found at:
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_the_sodium_potassium_pump_works.html
The sodium-potassium pump is a form of active transport. Its a lot easier to think of it in steps.
1. the protein has a high affinity for Na+, so cytoplasmic Na+ will bind to the protein.
2. This binding process stimulated the adding of a phosphate group (phosphorylation), by ATP. The energy from the ATP is enough to push the Na+ against its gradient.
3. the phosphorylation triggers the protein's changing shape. The shape change is accompanied with the the movement of Na+ against their gradient. The protein loses its high affinity for Na+ and they have now successfully moved across the gradient.
4. The new shape has a high affinity for K+. The K+ now bind to the protein. The binding of the K+ triggers the release of the phosphate group that changed the protein's shape in the first place.
5. With the phosphate gone, the protein reverts back to its original shape. Again, the shape change is accompanied with the movement of ions against their gradient; this time it's K+.
6. the old shape, as you may recall, has a high affinity for Na+ - it has lost its affinity for K+ and lets the ions go. These ions have now successfully crossed the membrane. As the protein has reverted to its old shape it is now available to bind to Na+ ions again, starting step 1 again. If you would like to continue, please go back to step 1. :)
Charged particles like Na and K ions move across membranes through transport proteins. I think the specific transport protein you're probably looking for is the Sodium-Potassium Pump, though it may be known under other names.
My grade 12 biology teacher (I live in Canada, if grade 12 sounds strange to you) showed us this really awesome video, which can be found at:
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_the_sodium_potassium_pump_works.html
The sodium-potassium pump is a form of active transport. Its a lot easier to think of it in steps.
1. the protein has a high affinity for Na+, so cytoplasmic Na+ will bind to the protein.
2. This binding process is stimulated the adding of a phosphate group (phosphorylation), by ATP. The energy from the ATP is enough to push the Na+ against its gradient.
3. the phosphorylation triggers the protein's changing shape. The shape change is accompanied with the the movement of Na+ against their gradient. The protein loses its high affinity for Na+ and they have now successfully moved across the gradient.
4. The new shape has a high affinity for K+. The K+ now bind to the protein. The binding of the K+ triggers the release of the phosphate group that changed the protein's shape in the first place.
5. With the phosphate gone, the protein reverts back to its original shape. Again, the shape change is accompanied with the movement of ions against their gradient; this time it's K+.
6. The old shape, as you may recall, has a high affinity for Na+, thus it has lost its affinity for K+ and lets the ions go. These ions have now successfully crossed the membrane. As the protein has reverted to its old shape it is now available to bind to Na+ ions again, starting step 1 again. If you would like to continue, please go back to step 1. :)
Charged particles cannot simply cross the plasma membrane. They use ion channels, such as a sodium potassium pump, to move across the membrane.
Through a specific protein channel.
Yes through a protein pump
ion pumps
Yes. It is called Osmosis. Particles move across the membrane in order to balance the concentration of particles on both sides of the membrane. Since the membrane tends to block the larger particles, its the smaller molecules that move, so what happens across membranes is that the motion (of say water) is from low concentration toward higher - but the result is to even the concentration on both sides of the membrane, Pure diffusion is always from higher concentration to lower.
active transport
Protein channels help move particles across the cell membrane
Large molecules are transported across a cell membrane by the process of process of exocytosis. This is when secretory vesicles secretes large molecules by the fusion of vesicles with the plasma membrane.
ion pumps
They are pumped actively.
Through channels in the bilipid layer. The channels use ATP to pump molecules against the ion gradient.
no, membranes are selectively permeable, letting somethings in and not others
Yes. It is called Osmosis. Particles move across the membrane in order to balance the concentration of particles on both sides of the membrane. Since the membrane tends to block the larger particles, its the smaller molecules that move, so what happens across membranes is that the motion (of say water) is from low concentration toward higher - but the result is to even the concentration on both sides of the membrane, Pure diffusion is always from higher concentration to lower.
Osmosis.
Electrons
Through Sodium-Potassium Pump Proteins. They are the key to a successful action potential, and eventually an impulse
electrons/charged particles.
Charged particles.
Diffusion ,osmosis
Diffusion ,osmosis