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How does the lipid bilayer form a barrier to molecules?
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+ Molecules
+ Lipids
+ Biochemistry
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Njabulo Twala
How does the lipid bilayer form a barrier to molecules?
If you are having trouble conceptualizing what is happening, then I’ll use a few analogies.
The primary deterrent for molecules passing through the lipid bilayer is polarity/charge. Certain molecules can either be polar or non-polar (roughly charged or uncharged). What makes a lipid bilayer interesting is that it has charged barriers at the inside and outside, and non-charged in the center. For a molecule to get across the lipid bilayer it must pass by both layers.
Most molecules are either charged or uncharged. This would make one of the two layers a problem. In that case think of trying to press two magnets together. You can get them close, but the closer you make them the more force that has to be applied to keep them there.
The second problem is that at the scale of the molecules, the lipid membrane is like the mixture of corn starch and water. It is dense. Anything that is going to pass through it is like Grand Central Station at rush hour. Something can make its way through if given enough time, but there is a substantial amount of resistance if you try to move through too quickly.
If we combine these together, then something that is highly charged or very non-polar will have trouble at one of the two layers. And, the solution to that is either of those molecules would have to pass through that layer very quickly. However, the density of the bilayer would be more resistant the faster the molecule tried to pass through.
Here is the last problem: the molecules are not generally propelled. Rather, most molecules are just passively floating around the extracellular fluid like floaties in a pool. It would be an anomaly to see a floatie spontaneously move at 20 mph across the pool. It just doesn’t happen.
In the current political climate, you could say that a molecule passing through the lipid bilayer is like a bill quickly passing through a split Senate chamber when there is no national press or lobbying around an issue. It is unusual. But it can happen. In endocrinology, steroids can pass across the membrane. In politics, you can usually get all senators to agree to increase their salaries (for the next term).
If you are having trouble conceptualizing what is happening, then I’ll use a few analogies.
The primary deterrent for molecules passing through the lipid bilayer is polarity/charge. Certain molecules can either be polar or non-polar (roughly charged or uncharged). What makes a lipid bilayer interesting is that it has charged barriers at the inside and outside, and non-charged in the center. For a molecule to get across the lipid bilayer it must pass by both layers.
Most molecules are either charged or uncharged. This would make one of the two layers a problem. In that case think of trying to press two magnets together. You can get them close, but the closer you make them the more force that has to be applied to keep them there.
The second problem is that at the scale of the molecules, the lipid membrane is like the mixture of corn starch and water. It is dense. Anything that is going to pass through it is like Grand Central Station at rush hour. Something can make its way through if given enough time, but there is a substantial amount of resistance if you try to move through too quickly.
If we combine these together, then something that is highly charged or very non-polar will have trouble at one of the two layers. And, the solution to that is either of those molecules would have to pass through that layer very quickly. However, the density of the bilayer would be more resistant the faster the molecule tried to pass through.
Here is the last problem: the molecules are not generally propelled. Rather, most molecules are just passively floating around the extracellular fluid like floaties in a pool. It would be an anomaly to see a floatie spontaneously move at 20 mph across the pool. It just doesn’t happen.
In the current political climate, you could say that a molecule passing through the lipid bilayer is like a bill quickly passing through a split Senate chamber when there is no national press or lobbying around an issue. It is unusual. But it can happen. In endocrinology, steroids can pass across the membrane. In politics, you can usually get all senators to agree to increase their salaries (for the next term).
If you are having trouble conceptualizing what is happening, then I’ll use a few analogies.
The primary deterrent for molecules passing through the lipid bilayer is polarity/charge. Certain molecules can either be polar or non-polar (roughly charged or uncharged). What makes a lipid bilayer interesting is that it has charged barriers at the inside and outside, and non-charged in the center. For a molecule to get across the lipid bilayer it must pass by both layers.
Most molecules are either charged or uncharged. This would make one of the two layers a problem. In that case think of trying to press two magnets together. You can get them close, but the closer you make them the more force that has to be applied to keep them there.
The second problem is that at the scale of the molecules, the lipid membrane is like the mixture of corn starch and water. It is dense. Anything that is going to pass through it is like Grand Central Station at rush hour. Something can make its way through if given enough time, but there is a substantial amount of resistance if you try to move through too quickly.
If we combine these together, then something that is highly charged or very non-polar will have trouble at one of the two layers. And, the solution to that is either of those molecules would have to pass through that layer very quickly. However, the density of the bilayer would be more resistant the faster the molecule tried to pass through.
Here is the last problem: the molecules are not generally propelled. Rather, most molecules are just passively floating around the extracellular fluid like floaties in a pool. It would be an anomaly to see a floatie spontaneously move at 20 mph across the pool. It just doesn’t happen.
In the current political climate, you could say that a molecule passing through the lipid bilayer is like a bill quickly passing through a split Senate chamber when there is no national press or lobbying around an issue. It is unusual. But it can happen. In endocrinology, steroids can pass across the membrane. In politics, you can usually get all senators to agree to increase their salaries (for the next term).
If you are having trouble conceptualizing what is happening, then I’ll use a few analogies.
The primary deterrent for molecules passing through the lipid bilayer is polarity/charge. Certain molecules can either be polar or non-polar (roughly charged or uncharged). What makes a lipid bilayer interesting is that it has charged barriers at the inside and outside, and non-charged in the center. For a molecule to get across the lipid bilayer it must pass by both layers.
Most molecules are either charged or uncharged. This would make one of the two layers a problem. In that case think of trying to press two magnets together. You can get them close, but the closer you make them the more force that has to be applied to keep them there.
The second problem is that at the scale of the molecules, the lipid membrane is like the mixture of corn starch and water. It is dense. Anything that is going to pass through it is like Grand Central Station at rush hour. Something can make its way through if given enough time, but there is a substantial amount of resistance if you try to move through too quickly.
If we combine these together, then something that is highly charged or very non-polar will have trouble at one of the two layers. And, the solution to that is either of those molecules would have to pass through that layer very quickly. However, the density of the bilayer would be more resistant the faster the molecule tried to pass through.
Here is the last problem: the molecules are not generally propelled. Rather, most molecules are just passively floating around the extracellular fluid like floaties in a pool. It would be an anomaly to see a floatie spontaneously move at 20 mph across the pool. It just doesn’t happen.
In the current political climate, you could say that a molecule passing through the lipid bilayer is like a bill quickly passing through a split Senate chamber when there is no national press or lobbying around an issue. It is unusual. But it can happen. In endocrinology, steroids can pass across the membrane. In politics, you can usually get all senators to agree to increase their salaries (for the next term).
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