aziel92 said:
Are these protocells spherical or just circular?
Spherical. They are about the size of bacteria.
I looked at the article with all the pictures and dealt more with the science. Have you ever taken oil and water and shaken it up a whole lot and then let it sit? because of the properties and water and oil the oil begins to form microscopic balls which gradually get bigger and bigger, they grow!! And then if you take a needle and gently poke one it will indent then reform and move away, it responded!! If you cut it in half it will form two balls of oil, it reproduced!
1. But the oil droplets don't have
metabolism, do they? And you need
all 4 properties to be alive. So oil droplets fail there.
2. You had to cut them in order for the "reproduction" to occur. You don't have to cut protocells to get them to divide. They do so on their own.
The formation of an oil droplet happens due to the chemical properties. Oil is what is called "hydrophobic", which means "water-hating". The molecules of oil don't interact well with the partially electrically charged water, so they cluster together to form the droplets.
Now, proteins do something similar. Many amino acids have side chains that are hydrophobic and a few amino acids have side chains that are hydrophilic -- water loving. A protein folds so that the hydrophobic side chains are in the middle all next to one another, excluding the water. The hydrophilic side chains are on the outside. The lipid bilayer of part of your cell membranes does much the same thing. However, 60% of your cell membranes are proteins!
The cell membrane of protocells is 100% protein, but they do the same thing. You have a shell with water on the outside and water on the inside.
The study sighted action potentials as prove for the cells responciveness.
That was
one of the ways the protocells respond. Movement is another. Also, shine light on the protocell and it engages in a primitive type of photosynthesis!
An action potential is very basically when the electrical charge changes in a substance.
An action potential occurs because the ability of the cell membrane to pass ions changes and sodium and potassium ions move across the cell membrane. So let's deal with a real action potential and not this strawman.
In cells this can be caused by very slight stimuli such as touch. In this experiment they used a small electrical charge. If you send an electrical charge through something that has a carboxylic acid group (the glutamic acid) then the charge is more than likely caused by the dissacioted H+ ion. Im really rather surprised as to why they were so surprised about this.
With the real explanation of an action potential, the surprise is now explained. Most cells do
not have an action potential. Liver cells don't, for example. Neither do bacteria. The surprise came because no one had any idea that the protocell membrane would selectively permit one ion -- potassium -- into the cell and exclude the other -- sodium. Bacteria don't do this.
Also some questions and critiques of the study: They did not mention if the amino acids were right or left handed. They did not show whether mixing all amino acids together or different combos of amino acids yielded the same results.
Doesn't matter about the handeness That was done in other studies. Protocells have been made with either and mixtures of both. However, this goes to the second question: did life actually arise this way.
And as long as glutamic acid is included in the mix, any combo of amino acids yields the same result. That is in the paper. This includes amino acids that are not used in proteins today.
Notice that the amino acids must be in the correct proportion (2;2:1).
I don't see any 2:2:1 ratio anywhere on the web page. I presume you are referring to Figure 4. If you mix 3 amino acids and they form peptides randomly, you should end up with 27 different peptides. But this didn't happen. Instead, you get only 6 out of the 27. That means that you have non-random formation of peptides.
They were surprised that they got nonrandom results but yet they used amino acids of which two can have a neg or partial neg charge side chains thus repelling each other
Glycine and tyrosine are neutral in the electrical charge. Only glutamic acid has a charge. Since your premise is wrong, the conclusion is wrong also.
If they did this experiment with say glycine, alanine and valine would the results be more random (they all have very similar side chains).
No. Been done. See reference list below.
Also I noticed that this reaction happened at 60 C meaning the water would very easily evaporate. Can this be repeated when the temp varies as it does on earth, under different pressures, at different NaCl concentrations. Is 1% the concentration of NaCl of early earth? Where does it describe these things metabolizing?
1. There is a table at the end of the page listing some of the metabolic activities observed.
2. The reaction occurs during dry heating over 100 C. In fact, the reaction occurs better if all the water does evaporate.
3. Yes, the reaction can occur under a wide variety of atmospheres and conditions. However, that is only relevant to question 2, not question 1.
Snyder WD and Fox, SW. A model for the origin of stable protocells in a primitive alkaline ocean. BioSystems 7: 222-229, 1975.
Rohlfing, DL. Thermal polyamino acids: synthesis at less than 100°C. Science 193: 68-70, 1976.
Syren RM, Sanjur A, Fox SW Proteinoid microspheres more stable in hot than in cold water. Biosystems 1985;17(4):275-80 (protocells at hydrothermal vents)
Yanagawa, H. and K. Kobayashi. 1992. An experimental approach to chemical evolution in submarine hydrothermal. systems. Origins of Life and Evolution of the Biosphere 22: 147-159.
Marshall, W. H. 1994. Hydrothermal synthesis of amino acids. Goechimica et Cosmochimica Acta 58: 2099-2106.
McAlhaney WW, Rohlfing DL. Formation of proteinoid microspheres under simulated prebiotic atmospheres and individual gases. Biosystems 1976 Jul;8(2):45-50
Fouche-CE Jr; Rohlfing-DL Thermal polymerization of amino acids under various atmospheres or at low pressures. Biosystems. 1976 Jul; 8(2): 57-65
Turcotte, PA, Paolillo, L, Ferrara, L, Benedetti, E, Andini, S. Structural characterization of thermal prebiotic polypeptides. J. Mol. Evol. 7: 105-110, 1976.
Rohlfing, DL. Thermal poly-a-amino acids containing low proportions of aspartic acid. Nature 216: 657-659, 1967.
Tyagi S, Ponnamperuma C Nonrandomness in prebiotic peptide synthesis. J Mol Evol 1990 May;30(5):391-9
Melius P. Structure of thermal polymers of amino acids. Biosystems 1982;15(4):275-80 Jul;8(2):45-50
SW Fox, Stereomolecular interactions and microsystems in experimental protobiogenesis. BioSystems 7: 22-36, 1975
SW Fox, Self-sequencing of amino acids and origins of polyfunctional protocells. Origins of Life, 14: 485-488, 1984.
Temussi, PA, Paolillo, L, Ferrara, L, Benedetti, I, Aninin, S. Structural characterization of thermal prebiotic polypeptides. J. Mol. Evol. 7: 105-110, 1976.
Pivcova, H, Saudek, V, Drobnik, J, Vlasak, J. NMR study of poly (aspartic acid) I. a- and b-peptide bonds in poly(aspartic acid) prepared by thermal polycondensation. Biopolymers 20: 1605-1614, 1981.
Nakashima, T, Jungck, JR, Fox, SW, Lederer, E, Das, BC. A test for randomness in peptides isolated from a thermal polyamino acid. Intl. J. Quantum Chem. QBS4: 65-72, 1977.
Bahn, P. and A. Pappelis. 2001. HPLC evidence of nonrandomness in thermal proteins. In First Steps in the Origin of Life in the Universe. Julián Chela-Flores, Tobias Owen, and François Raulin, eds., Kluwer Academic Publishers, Dordrecht, The Netherlands. Pp. 69-72.
Bahn, P. and A. Pappelis. 2001. IR spectra of protein, thermal protein, and thermal glycoprotein. In First Steps in the Origin of Life in the Universe. Julián Chela-Flores, Tobias Owen, and François Raulin, eds., Kluwer Academic Publishers, Dordrecht, The Netherlands. Pp.73-76.
Thermal proteins from DL and nonproteinous amino acids
Saunders MA and Rohlfing DL, Inclusion of nonproteinous amino acids in thermally prepared models for prebiotic protein. Biosystems 6. 81-92, 1974.
