Movement Across the Membrane (Osmosis ( , ), Active Transport (The body…
Movement Across the Membrane
The movement of particles down their gradients
A gradient is any imbalance in concentration
Moving down a gradient means that the particle is trying to be evenly distributed everywhere
Molecules most likely to be involved in simple diffusion are water molecules
When water goes under simple diffusion it is called
Molecules move down their gradients through the membrane
Molecules which practice simple diffusion are small and nonpolar
Can be disrupted is the diffusion distance is increased
E.g. alveolar in our lungs fill with fluid then the distance the gases travel increases, therefor their transport increases.
Facilitated diffusion is diffusion which is helped by a membrane transport channel.
Membrane transport channels are always specific for a certain molecule or a certain type of molecule (i.e. ion channel), they are tightly linked to certain physiologic function.
The body needs to sometimes move molecules against their gradient, this is known as moving uphill and requires energy which has been stored in the cell.
E.g. sodium potassium pump that helps maintain resting potential in the cell.
This protein uses energy released from the hydrolysis of the ATP (adrenosine phosphate) to pump three sodium iond out of and tow potassium ions into the cell. ATP is an energy molecule, when hydrolysis occurs, it gets broken down to release energy stored in the chemical bonds of the cell.
Transport that directly uses ATP molecules for energy is considered as
primary active transport
Proton pumps are responsible for creating the acidic environment of the stomach, causing acid reflex as well.
Secondary active transport
moves multiple molecules across the membrane, powering the uphill movement of molecules, with the downhill movement of others.
Glucose transporters which allow glucose into our cells (against the gradient) bring a sodium molecule as well
Since molecules are moved in the same direction this molecule is known as the
Proteins that allow molecules to go in the opposite directions are
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