/sci/ - Science & Math

>>6915560
>If they take the very edge of a cell and find lipids and they sublimate ice after they took off what they assumed was the top of the bilayer and see no change, how does that reconcile with your hypothesis?
What do you mean?
>they sublimate ice
>see no change
If they see no change, how do they know they anything sublimated?

>That's not at all what they mean by that.
It sounds like we are interpreting their abstract differently. If you can show me the full paper I'll read it, but otherwise it seems like this won't go anywhere if we can't agree on what they mean.

>It says they found lipids when they took a thin sheet off the very top of a cell, not from within the cell.
Lipids usually accumulate on top of water. Anyway, we really need a full paper, rather than trying to interpret an abstract.

>http://www.jbc.org/content/246/16/5162.full.pdf
I'm reading it now.

>>6915649
Then answer the question in the original post. When was the lipid membrane first proven? What experiment validated it?

>>6915571
Behold, sodium can enter cells and potassium can leave cells:
http://jp.physoc.org/content/134/2/278.full.pdf

Observations like these led to the invention of the Na/K ATPase. Which is strange, because a lipid membrane should prevent sodium from entering. This situation would be explained without a lipid membrane, but adding a lipid membrane necessitates the pumps. So rather than abandoning a model that did not match the evidence, they made the model more complicated to compensate. But what does the lipid membrane do? Something that is not observed.

>>6915571
>Citation needed
Do you disagree that sodium can enter cells and potassium can leave cells? This is the reason the sodium/potassium pump was invented.

>>6915579
Why bother proving your point when you can just declare you've already won? It's so simple! If only I'd thought of that!

>>6915598
That's your interpretation of the evidence. The actual evidence is just one or two dark rings around a cell.

>>6915560
Hold on. These responses either come in big waves or not at all.

>>6914596
>And how, exactly, does that refute direct analysis of the slices from >>6914488 ?
I don't think your link says what you think it says. It does not talk about a phospholipid bilayer. It just says they found some lipids in a blood cell. We don't even know exactly what they did, because all we have is an abstract (unless you have the full version, which I don't). They even admit that what they're seeing has "undergone considerable rearrangement from the original membrane." So either what they're seeing doesn't match what they expected to see or their methods genuinely disrupted the cell structure. Either way, I don't see any sentences saying "we found a phospholipid bilayer and were able to peel it off and examine it with freeze fracturing." It's more like "we found some lipids. Some of them were different from what we expected."

>For similar reasons these confluent ridges cannot be mere eutectic mixtures or organized, but nonmembrane, cytoplasmic components, as this would reduce the dimension of the biological membrane to that of a Euclidean plane.
The Euclidean plane has no width. Read that whole paragraph. They're trying to justify that what they're seeing is the lipid membrane. They say what they're seeing cannot be non-membrane components, because that would leave no space for a membrane; the membrane would need to be infinitesimally thin to fit. That's what a Euclidean plane is. Infinitesimally thin.

>What we're seeing cannot be non-membrane components because then the membrane would need to be infinitesimally thin to fit!

The other conclusion to draw is that the membrane simply isn't there.

I'm off to bed. I'll check this thread again in the morning.

>>6914525
>Do immunocytochemistry on highly hydrophobic molecules...they are localized to the membrane or found in lipid droplets.
Can you provide an example? People basically said the same thing to me about osmium tetroxide and it turned out to be totally different.

>>6914514
Okay, let's look at freeze-fracturing more closely. When I looked up freeze fracturing before, I found that later papers all assumed they were seeing the lipid membrane and cited earlier papers as justification. So I read the early, foundational papers that were being cited. Here's one:
http://www.pnas.org/content/55/5/1048.full.pdf

Read the "Discussion" section. The last sentence of the first paragraph. It's essentially saying, "this must be the lipid membrane, because we can't find any other space where it could be." That's not proving the lipid membrane; it's assuming it. Then later papers cite this one and now it's taken as fact.

>>6914483
Soap forms bubbles, which are somewhat analogous to a cell. Except bubbles are extremely fragile and the slightest disruption destroys them. Cells are amazingly resilient. I don't deny that lipids can form micelles, but I don't think cells are such an object.

>>6914486
From your link:
>No membrane-associated particles are observed.

>>6914466
Ha. Someone is impersonating me, so I'm using this hash code now. That's annoying.