Why are all naturally occuring amino acids in L-configuration? Is there an advantage to this?
408385
yep, basically it was by chance.  there is no advantage to having the L over the D configuration.  It an be inferred that originally amino acids occurred as racemic mixtures and some life forms used D while others used L. And by chance through evolution the L-configuration species survived.
560711
Phenylalanine occurs in two chemical forms: L-phenylalanine, a natural amino acid found in proteins; and its mirror image, D-phenylalanine, a form synthesized in a laboratory. Some research has involved the L-form, others the D-form, and still others a combination of the two known as DL-phenylalanine. \n\nIn the body, phenylalanine is converted into another amino acid called tyrosine. Tyrosine in turn is converted into L-dopa, norepinephrine, and epinephrine, three key neurotransmitters (chemicals that transmit signals between nerve cells). Because some antidepressants work by raising levels of norepinephrine, various forms of phenylalanine have been tried as a possible treatment for depression. \n\nD-phenylalanine (but not L-phenylalanine) has been proposed to treat chronic pain. It blocks enkephalinase, an enzyme that may act to increase pain levels in the body. \n\nThe long-term safety of phenylalanine in any of its forms is not known. Both L- and D-phenylalanine must be avoided by those with the rare metabolic disease phenylketonuria (PKU). \n\nThe maximum safe dosages of phenylalanine have not been established for young children, pregnant or nursing women, or those with severe liver or kidney disease.\n\nThere are some indications that the combined use of phenylalanine with antipsychotic drugs might increase the risk of developing the long-term side effect known as tardive dyskinesia, or worsen symptoms in those who already have it. \n\nLike other amino acids, phenylalanine may interfere with the absorption or action of the drug levodopa which is used for Parkinson's disease.
39430
Some believe that before DNA and protein, life existed in the form of RNA, evidenced by catalytic RNA in existence today (forming part of the ribosome: a protein building cellular machine) \n\nLess philosophically, amino acids (of which there are 20 types) are put together in sequences predetermined by DNA sequences. These DNA sequences are transcribed (copied) into an intermediary molecule of RNA, which is "read" by the ribosome (which gathers the correct amino acids to build the protein)
209909
try\nhttp://web.indstate.edu/thcme/mwking/amino-acids.html
1119706
Very simple. \n\nThere are two possibilities of we being here. Either we are here by Chance or we have been Created.  \n\nWhat are we made from? Cells. Let us now put aside the question of "how the first cell originated" and ask a much easier question: How did the first protein originate? The theory of evolution has no answer to this question either.\n\nProteins are made up of molecules, called "amino acids". There are 500-1,000 amino acids in an average protein. The important point is that amino acids have to line up in a certain sequence to form a protein. There are 20 different amino acid types used in living organisms. These amino acids do not combine at random to form proteins. Every protein has a certain amino acid sequence and this sequence must be precisely matched. Even the deficiency or the replacement of a single amino acid renders that protein a useless lump of molecules. For this  reason, every amino acid must be just at the right place in the right sequence. The instructions for this sequence are stored in the DNA of the cell and, according to them, the proteins are produced.\n\nThe theory of evolution claims that the first proteins formed "by chance". Probabilistic calculations, however, show that this is by no means possible. For instance, the probability of the amino acid sequence of a protein made up of 500 amino acids being in the correct order is 1 in 10^950.\n10^950 is an incomprehensible figure formed by placing 950 zeros after 1. In mathematics, a probability smaller than 1 over 1050 is considered to be almost impossible.\n\nEven a single protein cannot form by chance, and there are billions of Protein in human body. and there are billions of people here in this world. Calculation would be [ 10^950 x Number of protein molecules in human body x number of people in the world ever existed ]. Can you imagine this figure. The probability that human life can form by chance is nothing but 0. \n\nFinally, the time necessary for the molecule to form was 10^243 billion years. This was far greater than the supposed age of the universe - only about 2 billion years. It was impossible for the universe to have created itself, and for life to randomly form. \n\nThe only answer left is that there is creation, and when there is a creation , there is a CREATOR. \n\n"Say: ‘Call upon Allah, or call upon Rahman: by whatever name ye call upon Him, (it is well): for to Him belong the Most Beautiful Names....‘"\n                                  [Al-Qur’an 17:110]\n\n"Say: He is Allah,  The One and Only. "Allah, the Eternal, Absolute.\n"He begets not, nor is He begotten. And there is none like unto Him."  \n[Quran 112:1-4]\n \n\n \n\nhttp://www.evidencesofcreation.com/
378466
banana has amino acid\n\nÆ
188345
There's a flaw in your analogy. In DNA, it doesn't matter what letter order you use, you still get a valid word. It's just that, in any given sentence, in any given position in the sentence, the vast majority of words don't help convey the overall meaning of the sentence.\n\nEvery codon codes for SOMETHING (an amino acid, unless it's a "start" or "stop" codon), but not all arrangements of amino acids into proteins aid the survival of any given organism (in fact, only a small percentage might, given the right circumstances)
410782
We don't detect amino acids in stars directly, they need a much cooler environment to form and stay together.  We have found them in asteroids and comets within our own solar system, and have observed them in clouds of insterstellar gas.\n\nThe "we are all made of stardust" comment comes from the relization that all of the elements heavier than hydrogen and helium are created in the cores of stars, or in the violent deaths of some stars.  All the elements that make up you, me, this planet, everything were formed inside of stars and then blown out upon the cosmos to be reincorporated into new structures.  Kind of neat actually.
417571
First off - it's differenTiate not differenciate, terTiary not terciary.\n\nSpelling is important in science - make sure you pay attention to it.\n\nPrimary structure = the sequence of amino acids in the\n                    polypeptide chain; each amino acid \n                    joined to the next by a peptide bond.\n\nSecondary structure = the folding of the polypeptide chain \n                      to form a repeating 3D structure,\n                      whose shape is maintained by hydrogen\n                      bonds, typically forming alpha \n                      helices ( look like springs ) or beta\n                      pleated sheets ( like a sheet of paper\n                      with many folds along its length ).\n\nTertiary structure  = the folding of secondary structure \n                      into a new, more complex 3D shape held\n                      together by ionic, covalent and \n                      hydrogen bonds.\n                      \n                      Many proteins stop at this level.\n\nQuaternary structure = association of multiple polypeptide\n                       chains to form a multimeric structure\n                       held together by all the types of \n                       bonds mentioned for tertiary \n                       structure.\n\nAND PLEASE PLEASE PAY ATTENTION TO SPELLING - for example\nPropane and Propene only differ in one letter but they sure as Hell have different behaviours - this could result in an accident if one were used instead of the other in a laboratory or industrial setting!!
801238
There is no real model yet for the origin of life. However a number of discoveries have been made concerning the origin of molecular and cellular components that are necessary for life on earth:\n\n1. Conditions that existed 4.5x10^9 years ago result in the creation of certain basic small molecules of life, such as amino acids. This was demonstrated in the Urey-Miller experiment in the 50s.\n\n2. Fat molecules can organise spontaneously into layers which form the basis of cell membranes.\n\n3. Amino acids polymerize spontaneously into random RNA molecules.\n\n4. The resulting molecule soup will compete for resources, by which I mean smaller molecules, to be able to grow further. Therefore there will be selection pressures for efficiency and diversity which will favour those macromolecules that can reproduces themselves or part of themselves most quickly and efficiently.\n\n5. Thus evolution begins: once certain molecules are formed in the soup that can reproduce itself partly, they will soon dominate in the mix. In the next step the *better* ones among those will be selected and so on.\n\nTo summarize:\nWhen: between 4.5 and 2.5 billion years ago\nWhere: in water ponds at the surface of the earth\nWhy: any mixture of organic molecules will change into a mix of more complex molecules by polymerization\nHow: Selective pressure will favour those molecules that react faster and more efficient.
73683
Like all amino acids, lysine functions as a building block for proteins. It's also a key player in the production of various enzymes, hormones, and disease-fighting antibodies.\n\nMany foods supply lysine, but the richest sources by far include red meats, fish, and dairy products (milk, eggs, cheese).
289586
The function of a protein depends on its shape.  If you alter the shape of it, you alter its function.  pH is a factor that can alter the shape, because the pKa values of residues on the protein will dictate which residues are or are not protonated, and that will, in turn, affect the manner in which the various amino acids will form internal ionic bonds.\n\nTemperature is another factor.  the stability of intramolecular bonding is dependent on the level of thermal excitation.  If a protein is at a high temperature, the thermal motion of the atoms might upset their abilities to form bonds.  At really high heat, the result will be total denaturation.  At low temperatures, you might even have the opposite problem, with a protein clinging to things in the wrong ways.\n\nFinally, you might alter it by introducing a chemical that reacts with it.  Some proteins need activator molecules to function, others might be inactivated by an inhibitor.  Enzymatic activity occurs in what is called the "active site" of the protein, which is where the substrates bind to the protein and catalysis occurs.  So the activity of the molecule might be altered by changing the arrangement of the moieties in the acive site relative to one another, of there might be a change which permits/blocks access to the active site by the substrate molecules.
960830
Proteins, amino acids.
807216
All types of Ribosomes make amino acids.  Many amino acids are called proteins. Once the proteins are made, they are traveled to the ER, endoplasmic reticulum.  Then the ER delivers the proteins to the other organelles of the cell.  I hope this answers your answer.  I also know how the ribosomes make the protein. =)
670967
During protein synthesis, 20 different amino acids can be incorporated in proteins. After translation, the posttranslational modification (PTM) of amino acids extends the range of functions of the protein by attaching to it other biochemical functional groups such as acetate, phosphate, various lipids and carbohydrates, by changing the chemical nature of an amino acid (e.g. citrullination) or by making structural changes, like the formation of disulfide bridges.\n\nPTMs involving addition include:\n\nacetylation, the addition of an acetyl group, usually at the N-terminus of the protein \nalkylation, the addition of an alkyl group (e.g. methyl, ethyl) \nmethylation the addition of a methyl group, usually at lysine or arginine residues. (This is a type of alkylation.) \nbiotinylation, acylation of conserved lysine residues with a biotin appendage \nglutamylation, covalent linkage of glutamic acid residues to tubulin and some other proteins. \nglycylation, covalent linkage of one to more than 40 glycine residues to the tubulin C-terminal tail \nglycosylation, the addition of a glycosyl group to either asparagine, hydroxylysine, serine, or threonine, resulting in a glycoprotein \nisoprenylation, the addition of an isoprenoid group (e.g. farnesol and geranylgeraniol) \nlipoylation, attachment of a lipoate functionality \nphosphopantetheinylation, the addition of a 4'-phosphopantetheinyl moiety from coenzyme A, as in fatty acid, polyketide, non-ribosomal peptide and leucine biosynthesis \nphosphorylation, the addition of a phosphate group, usually to serine, tyrosine, threonine or histidine \nsulfation, the addition of a sulfate group to a tyrosine.
44003
amino acids, but the whole experiment was biased. why? they assumed that the first chemicals in the "primordial pool" were methane, ammonia, hydrogen and water. there is debate on this now because NASA has determined that the earth's "primordial soup" was not made of that. Water, oxygen and nitrogen seem to be more along the lines of reality. besides, linking amino acids together to form proteins is remarkably easy. if you are smart. by chance it "is about the same as the probability that a tornado sweeping through a junk yard could assemble a 747 from the contents therein" as Fredrick Hoyle has said (smart beyond belief, but weird)
77216
Exactly what it makes depends on how the molecules are hooked together--sugars and amino acids are complex and can be joined in multiple spots.  Amino acids are used primarily to build proteins, and some proteins have sugars added to them--this is particularly common for proteins that are placed on the cell surface.  It is also common for phosphates to be added to amino acids, and this is often used as a switch; a protein might be off until a phosphate is added to an amino acid, or vice versa.    A similar process is ADP-ribosylation, in which a molecule consisting of an adenine, 2 ribose sugars and 2 phosphates is added to an amino acid in a protein.  Some toxins such as pertussis toxin inactivate their cellular target through ADP-ribosylation.\n\nOne type of molecule that is similar to what you are asking about is a nucleotide.  It contains a sugar and a phosphate, but not an amino acid; instead it has a nitrogenous base (A, C, T, or G).