what distinguishes a protein from a polypeptide?
100527
In simple terms it is function. A protein is a polypeptide, but it is a polypeptide that does something. It has a purpose.\n\nYou can of course also have polypeptides that are just junk. They don’t do anything. Chemically they belong to the same class as proteins but they lack a function.\n\nJazzSinger said  “A polypeptide is a protein in the making”. That isn’t true, In fact most polypeptides are exactly the opposite: they are proteins in the process of being destroyed.  Food is loaded with non-protein polypeptides, not because proteins are being made in food but because the cooking process destroys proteins.
74693
I asked this same question at the Wikipedia reference desk not long ago. See below for a summary of the answer. (It discusses both protein length- the number of amino acids and molecular weight):\nI am looking for a rule of thumb on the molecular weight of proteins. Any opinion of the "average" MW of proteins? Or the range of MW that most proteins fall in? I know this is an ill defined question, so don't bother telling me that..... ike9898 22:32, 3 January 2006 (UTC)\n\nA molecular mass of about 40,000 is fairly average. Proteins such as myoglobin and calmodulin are good examples of proteins that do not try to do a whole lot, but they show that a particular biological function can often be accomplished with a 15-20 kDa protein. Many proteins combine several functional domains and can easily be 40, 60, 80, 100 kDa. Many membrane proteins have multiple transmembrane domains plus a cytoplasmic and an extracellular domain. Transmembrane proteins in the range of 80-160 kDa are fairly common. Attempts have been made to identify all the proteins in various organisms. In Mycoplasma hyopneumoniae the average protein size is 388 amino acids (see). The recent article, "Protein length in eukaryotic and prokaryotic proteomes" says that among the Eukaryotic proteins analyzed the average protein was 361 amino acids long while in Bacteria the average was 267 amino acids. --JWSchmidt 00:05, 4 January 2006 (UTC) \n\nThank you! Using another rule of thumb (number of amino acids times 110 = estimate of MW): \n388 amino acids represents a MW of about 42.6 kDa \n361 """" 39.7 kDa \n267 """" 29.4 kDa
960830
Proteins, amino acids.
543572
Its the primary structure...\nSecondary refers to the arrangement of protein residues in realtion to one another. alpha helix beta strand etc...\nTertiary is the big picture-what these things actaully look like. Quaternary structure is the comming together of of the teriary subunits.
151434
Biopolymers are just naturally occuring polymers.  A polymer is any molecule where small units link together to make a chain of subunits.  Examples in industry are plastics, but in biology, polymers are seen in peptide chains (used for builiding proteins), DNA (which controls the form and function of an organism by encoded the information that is needed to assemple petide chains to make proteins), charbohydrates (chains of sugars that can serve to store energy or serve structural purposes, like glycoprotein recognition molecules that are on the outsides of cells), and lipids (fatty acid chains that also store energy or serve to make structures, like cell membranes).\n\nAdditionally, proteins of a similar type like actin can polymerize, to create a super-protein that have important functions in cell structure and motility.\n\nThe components of these are nucleotides for DNA, amino acids for peptide chains/proteins, sugars for carbohydrates, and CH2 units for lipids (so-called saturated fats are chains of carbon atoms with two hydrogens bonded to each carbon atom).
885040
the building blocks of protein
782832
the peptide bond of protein is the bond formed between the carbonyl carbon of one amino acid and the nitrogen atom another amino acid. this is how the amino acids binds with eachother to form  the polypeptide chain and consequently the protein.
582504
Another important thing to note about an enzyme is that it isn't used up in the reaction, so it can be recycled over and over. An enzyme is a protein that helps in a chemical reaction to speed it up. Enzymes are very specific in the reactions that they will interact with. An enzyme will only catalyze its own reaction.
944914
it's almost the same theory but the stuff (eg, buffers and gel types) used are different. Also proteins separate according to their molecular weight and DNA separate according to their base pairs.
1166289
proteins contain 20 Amino acids connected by dipeptide linkages. \n\neach and every amino acid has unique structure and properties, so when they are connected like beads in a chain, of 20 colours to simplify, arrangement can be made in millions of ways which makes it unique.\n\nso diversity comes from the arrangement of amino acids that is called Sequence which is represented in 20 diff alphabets \n\n   Alanine\n   Arginine\n   Asparagine\n   Aspartic acid\n   Cysteine\n   Glutamic acid\n   Glutamine\n   Glycine\n   Histidine\n   Isoleucine\n   Leucine\n   Lysine\n   Methionine\n   Phenylalanine\n   Proline\n   Serine\n   Threonine\n   Tryptophan\n   Tyrosine\n   Valine\n\nwhile giving this answer I came through similar analogy in the source given below that might give you a feel for the subject.
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!!
81113
Chemical Formula: \nCasein proteins are composed of the following amino acids: \n20.2% Glutamic Acid \n10.2% Proline \n 8.3% Leucine* \n 7.4% Lysine* \n 6.5% Valine* \n 6.4% Aspartic Acid \n 5.7% Serine \n 5.7% Tyrosine \n 5.5% Isoleucine* \n 4.5% Phenylalanine* \n 4.4% Threonine* \n 3.7% Arginine \n 2.8% Histidine \n 2.7% Alanine \n 2.5% Methionine* \n 2.4% Glycine \n 1.1% Tryptophan* \n 0.3% Cystine
115334
Generally polyclonal anitbodies are used to bind non-specifically to antigens. For instance, you might use monoclonal antibodies to specifically bind to your protein of intererst. You might then use polyclonal Ab to bind the rest of the proteins i.e. to block off the other available 'slots'
1068983
An epitope is the part of a macromolecule that is recognized by the immune system, specifically by antibodies, B cells, or cytotoxic T cells. Although usually epitopes are thought to be derived from nonself proteins, sequences derived from the host that can be recognized are also classified as epitopes.\n\nMost epitopes can be thought of as three-dimensional surface features of an antigen molecule; these features fit precisely and thus bind to antibodies. The part of an antibody that recognizes the epitope is called a paratope. Exceptions are linear epitopes, which are determined by the amino acid sequence (the primary structure) rather than by the tertiary structure of a protein.\n\nEpitopes can be mapped using protein microarrays, and with the ELISPOT or ELISA techniques.\n\nGenetic sequences coding for epitopes that are recognised by common antibodies can be fused to genes, thus aiding further molecular characterization of the gene product. Common epitopes used for this purpose are c-myc, HA, FLAG, V5.\n\nInterestingly, epitopes are sometimes cross-reactive. This property is exploited by the immune system in regulation by Anti-idiotypic antibodies (originally proposed by Nobel laureate Niels Kaj Jerne). If an antibody binds to an antigen's epitope, the paratope could become the epitope for another antibody that will then bind to it. If this second antibody is of IgM class, its binding can upregulate the immune response; if the second antibody is of IgG class, its binding can downregulate the immune response.\n\nIntensive research is currently taking place to design reliable tools that will predict epitopes on proteins.
759955
Maybe.\n\nSerum protein electrophoresis generally separates the proteins into five distinct bands.  For such different creatures, I would expect the population of the various bands to be fairly different, and therefore it would be a good tool to distinguish between those different species, I suppose.\n\nIf, on the other hand, you wanted to compare SPECIFIC proteins in these different creatures, electrophoresis would probably be a poor way to get a good sample.  I'm thinking the right kind of chromatograph or a targetted binding reaction would be better for that.
534415
pancreatic polypeptide  ?? \nTry the web site it may help.
613241
Polymer is a generic term used to describe a very long molecule consisting of structural units and repeating units connected by covalent chemical bonds.  The key feature that distinguishes polymers from other molecules is the repetition of many identical, similar, or complementary molecular subunits in these chains. These subunits, the monomers, are small molecules of low to moderate molecular weight, and are linked to each other during a chemical reaction called polymerization.