Cells

[ydoaPs]

Last year I had to take a bio class. Early in the book, it talks about Cell Theory. In second semester it talked about cells evolving from bubbles of lipids(it had a name for them, but i don't remember it). They aren't compatible. Which one is in the standard model for biology?

[admiral_ju00]

The cell theory is.

I've not heard of that other one.

 

As for that 2nd one, are you sure you're not talking about a cell membrane as opposed to an actual theory?

[DimShadow7]

I think the other thing with the cells bubbling out of puddles of lipids is called chemical evolution. I have a vague memmory of this but I remember that both were compatible to some extent. Could you expand on why they are not compatabile?

 

Thanks,

DimShadow7

[ydoaPs]

part of cell theory is "cells only come from other cells". i was not confusing it with cell membrane. i was talking about these bubbles of lipids that my bio book said cells evolved from.

[Sayonara]

When you say "evolved", do you mean the historical structure of cells as a group, or the development of a single cell?

[ydoaPs]

the first cell

[LucidDreamer]

"Micelles form from amphipathc lipids that position the hydrophobic tails in the center of the lipid aggregations with the polar head groups facing outward" Micelles form spontaneously when amphipathic lipids are placed in water. It has been suggested that the first cell was just a piece of DNA or RNA, capable of reproducing, contained within a micelle. Because they lack fossil records they really have no idea what life was life before the earliest found prokaryotes.

[admiral_ju00]

It has been suggested that the first cell was just a piece of DNA or RNA, capable of reproducing, contained within a micelle.

 

I don't think it could have been the DNA. RNA, is a better candidate.

[Skye]

Even RNA is a bit tricky as a starting point, as polymers of RNA don't form very easily. So it may have been something similar, but not quite the same.

 

Anyway, cells are bubbles of lipids (with lots of other stuff) so it's not really contradictory to say that cells formed from bubbles of lipids. Whether they actually did or not is very difficult to say though.

[ydoaPs]

cell theory makes it contradictory.

 

i don't think a piece of random RNA in a lipid bubble counts as life. there was no metabolism or reproduction capabilities

[Sayonara]

We call things like erythrocytes "cells".

[ydoaPs]

what is wrong with calling red blood cells cells?

[Sayonara]

They have no metabolism or reproduction capabilities, which are the criteria by which you claimed "a piece of random RNA in a lipid bubble" is not a cell.

[ydoaPs]

"a piece of RNA in a lipid bubble" is not produced by a cell; red blood cells are.

I should have phrased post #10 better. when i said it wasn't a cell, i meant it wasn't life.

[ydoaPs]

my point is "a piece of DNA in a lipid bubble" is not produced by cells, so it shouldn't be considered a cell.

[LucidDreamer]

"Cells are the basic units of life. They are the building blocks of all organisms, from bacteria to animals. Cells are thought to be the units for life. This is stated in the cell theory. The cell theory is as follows:

 

1. All living things are composed of one or more cells.

2. Cells are organisms' basic units of structure and function.

3. Cells come only from existing cells."

 

Cell theory only applies to life today. Saying that early life and proto-cells don't adhere to the principles of cell theory is like saying early mammal ancestors don't meet the qualifications of mammals--such as warm-blood, mammary glands, fur, etc. Of course mammal ancestors don't meet the qualifications. Before there were mammals there were no mammals. Before there were modern cells that meet the qualifications of cell theory there were proto cells that acquired the modern characteristics as they evolved.

[ydoaPs]

early mammal ancestors weren't mammals they were early mammal ancestors. photosynthetic protists were the ancestors of plants, but they aren't plants.

[admiral_ju00]

early mammal ancestors weren't mammals they were early mammal ancestors. photosynthetic protists were the ancestors of plants, but they aren't plants.

 

And your point being....?!?

[ydoaPs]

"

Saying that early life and proto-cells don't adhere to the principles of cell theory is like saying early mammal ancestors don't meet the qualifications of mammals--such as warm-blood' date=' mammary glands, fur, etc. Of course mammal ancestors don't meet the qualifications. Before there were mammals there were no mammals. [/quote']

 

he said that protocells didn't obey cell theory, because early mammal ancestors didn't have all the qualities of mammals. i said early mammal ancestors weren't mammals, so that argument is useless.

[LucidDreamer]

he said that protocells didn't obey cell theory, because early mammal ancestors didn't have all the qualities of mammals. i said early mammal ancestors weren't mammals, so that argument is useless.

 

hmm, that’s not what I was trying to say. I was trying to say that there is no use in applying cell theory to early proto-cells because that theory was intended for modern cells. However, I suggested that early cells could have been pieces of RNA (that’s for admiral ju) capable of reproducing within micelles. This organism would qualify for all of the cell theory principles. Except of course for the first cell ever which would not qualify under the 3rd requirement.

[ydoaPs]

a piece of RNA in a lipid bubble cannot reproduce. it would need other chemicals to replicate the RNA. how would it devide.

[LucidDreamer]

Modified RNA and RNA derivatives can perform certain chemical functions but beyond that I have no idea how early cells replicated. If I did I would have already picked up my Nobel Prize.

[Skye]

Well using the mammal analogy, I can postulate that all mammals come from pre-existing mammals. All observations of mammal reproduction support this position. But of course, at some point a mammal was born from something that wasn't a mammal. That was the start of mammaldom.

[Arg]

Of course you're running into problems reconciling everything: it's all a classification issue. There aren't any mammals, or reptiles, or bacteria, just stuff on a spectrum grouped for convenience. You can say that a mammal is a being with all these various characterstics, and you can convincingly lie to yourself about that most of the time, but if you go backwards in their evolution you'd run across creatures so close to mammals it'd be hard to tell the difference. At that point, all that separates this from that is a wish and a whim. Too many so-called scientists forget that.

[Sayonara]

Whooooooooooooooooooooosh.

 

Watch out for low-flying points.