3 Major Ways Small Molecules Can Cross Membrane

3 Major Ways Small Molecules Can Cross Membrane - 3 Major...

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3 Major Ways Small Molecules Can Cross Membrane: 1. Simple Diffusion (or Passive) - the smaler and more fat soluble, the faster the molecule can penatrate the membrane. These include CO2, O2, N2, non-polar, uncharged. Passive Transport is a "downhill" energy gradient, meaning there is no input of energy for the molecule to cross over. Water (although it is polar) can cross a membrane rapidly Molecules in asolution go form high concentration to low concentration..."move downhill" on the energy gradient. 2. Facillitated Diffusion: a normal process of diffusion were a molecule is helped or facillitated by membrane proteins to get across membrane. This is selectrive. 3. Active Transport: The "uphill" movement of on the energy gradient. The molecule is moved against electrochemical gradient. There is can input of energy (hydrolysis of ATP). The transport is always done by a carrier protein. Carriers are transporter proteins that bind specific molecule or ions and transfer them across the membrane. They can change conformation or shape to transport materials.
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