DIFFUSION THROUGH A CELL MEMBRANE
Start studying Explain the relationship between diffusion and concentration gradients. Learn vocabulary, terms, and more with flashcards, games, and other. Covers selective permeability of membranes, diffusion, and facilitated diffusion In cells, some molecules can move down their concentration gradients by. Particles will diffuse down the concentration gradient until equal concentration is achieved in all areas.
Passive transport does not require the cell to expend any energy and involves a substance diffusing down its concentration gradient across a membrane.
Diffusion ( Read ) | Biology | CK Foundation
A concentration gradient is a just a region of space over which the concentration of a substance changes, and substances will naturally move down their gradients, from an area of higher to an area of lower concentration.
In cells, some molecules can move down their concentration gradients by crossing the lipid portion of the membrane directly, while others must pass through membrane proteins in a process called facilitated diffusion. Selective permeability The phospholipids of plasma membranes are amphipathic: The hydrophobic core of the plasma membrane helps some materials move through the membrane, while it blocks the movement of others.
Structure of a phospholipid, showing hydrophobic fatty acid tails and hydrophilic hea.
A bilayered membrane consisting of phospholipids arranged in two layers, with their heads pointing out and their tails sandwiched in the middle, is also shown. Image modified from OpenStax Biology.
Polar and charged molecules have much more trouble crossing the membrane. Polar molecules can easily interact with the outer face of the membrane, where the negatively charged head groups are found, but they have difficulty passing through its hydrophobic core.
Water molecules, for instance, cannot cross the membrane rapidly although thanks to their small size and lack of a full charge, they can cross at a slow rate.
How is a concentration gradient related to the process of diffusion? | Socratic
Additionally, while small ions are the right size to slip through the membrane, their charge prevents them from doing so. Larger charged and polar molecules, like sugars and amino acids, also need help from proteins to efficiently cross the membrane. Diffusion In the process of diffusion, a substance tends to move from an area of high concentration to an area of low concentration until its concentration becomes equal throughout a space.
For example, think about someone opening a bottle of cleaning ammonia in the middle of a room. The ammonia molecules will initially be most concentrated right where the person opened the bottle, with few or no molecules at the edges of the room.
Ultimately, if the bottle is capped and the room is closed, the ammonia molecules will become evenly distributed throughout its volume.
Facilitated diffusion can increase the rate of diffusion of particular molecules at low concentrations. However, the rate of facilitated diffusion levels off with increasing solute concentration.
Additional increases in external solute concentration cannot increase the rate of diffusion once carrier proteins are saturated. Passive diffusion of solute into a cell is linearly related to the concentration of solute outside the cell.
What is the relationship between diffusion and concentration gradient?
Carrier proteins increase the rate of diffusion by allowing more solute to enter the cell. Facilitated diffusion, however, approaches a maximum rate as the carrier proteins become saturated with solute. What is the slope of this line? What do increases or decreases in the slope mean biologically?
And so if we looked at its concentration gradient, so the concentration gradient went from high concentration on the left to low concentration on the right. And we saw what happened. Since you have more of these particles here and they're all bouncing around in different directions randomly, you have a higher probability of things moving from the left to the right than from the right to the left.
You will have things move from the right to the left, but you're going to have more things, so you'll have a higher probability of things, moving from left to right. And so if you let some time pass, then they become more uniformly spread across a container. They have moved down their concentration gradient to make things more uniform. Now, what's interesting about this diagram is I've introduced a second particle, these big yellow particles.
And we see that their concentration gradient is going in the other direction.