What is Amino acids: Definition and 39 Discussions

Amino acids are organic compounds that contain amino (–NH2) and carboxyl (–COOH) functional groups, along with a side chain (R group) specific to each amino acid. The key elements of an amino acid are carbon (C), hydrogen (H), oxygen (O), and nitrogen (N), although other elements are found in the side chains of certain amino acids. About 500 naturally occurring amino acids are known as of 1983 (though only 20 appear in the genetic code) and can be classified in many ways. They can be classified according to the core structural functional groups' locations as alpha- (α-), beta- (β-), gamma- (γ-) or delta- (δ-) amino acids; other categories relate to polarity, pH level, and side chain group type (aliphatic, acyclic, aromatic, containing hydroxyl or sulfur, etc.). In the form of proteins, amino acid residues form the second-largest component (water is the largest) of human muscles and other tissues. Beyond their role as residues in proteins, amino acids participate in a number of processes such as neurotransmitter transport and biosynthesis.
In biochemistry, amino acids which have the amine group attached to the (alpha-) carbon atom next to the carboxyl group have particular importance. They are known as 2-, alpha-, or α-amino acids (generic formula H2NCHRCOOH in most cases, where R is an organic substituent known as a "side chain"); often the term "amino acid" is used to refer specifically to these. They include the 22 proteinogenic ("protein-building") amino acids, which combine into peptide chains ("polypeptides") to form the building blocks of a vast array of proteins. These are all L-stereoisomers ("left-handed" isomers), although a few D-amino acids ("right-handed") occur in bacterial envelopes, as a neuromodulator (D-serine), and in some antibiotics.Twenty of the proteinogenic amino acids are encoded directly by triplet codons in the genetic code and are known as "standard" amino acids. The other two ("nonstandard" or "non-canonical") are selenocysteine (present in many prokaryotes as well as most eukaryotes, but not coded directly by DNA), and pyrrolysine (found only in some archaea and one bacterium). Pyrrolysine and selenocysteine are encoded via variant codons; for example, selenocysteine is encoded by stop codon and SECIS element. N-formylmethionine (which is often the initial amino acid of proteins in bacteria, mitochondria, and chloroplasts) is generally considered as a form of methionine rather than as a separate proteinogenic amino acid. Codon–tRNA combinations not found in nature can also be used to "expand" the genetic code and form novel proteins known as alloproteins incorporating non-proteinogenic amino acids.Many important proteinogenic and non-proteinogenic amino acids have biological functions. For example, in the human brain, glutamate (standard glutamic acid) and gamma-aminobutyric acid ("GABA", nonstandard gamma-amino acid) are, respectively, the main excitatory and inhibitory neurotransmitters. Hydroxyproline, a major component of the connective tissue collagen, is synthesised from proline. Glycine is a biosynthetic precursor to porphyrins used in red blood cells. Carnitine is used in lipid transport. Nine proteinogenic amino acids are called "essential" for humans because they cannot be produced from other compounds by the human body and so must be taken in as food. Others may be conditionally essential for certain ages or medical conditions. Essential amino acids may also vary from species to species. Because of their biological significance, amino acids are important in nutrition and are commonly used in nutritional supplements, fertilizers, feed, and food technology. Industrial uses include the production of drugs, biodegradable plastics, and chiral catalysts.

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  1. nomadreid

    Distribution of amino acids in different proteins

    In https://en.wikipedia.org/wiki/Selenocysteine , I read: "As of 2021, 136 human proteins (in 37 families) are known to contain selenocysteine (selenoproteins)." This seems to indicate (my knowledge of biochemistry being close to zero) that this amino acid is not found throughout the human...
  2. Dhh1994

    Can pH of a His buffer change during lyophilization?

    We lyophilized 50mg/ml mAb with PI of 7.5 in a 10mM His buffer pH 6.2. Upon reconstitution the pH is 6.5. Does anyone have an explanation for this? I am under the impression His is much less susceptible to pH change during lyophilization as opposed to something like a phosphate buffer. Thanks.
  3. I

    Different amino acids in different life forms?

    Hello, Are the 20 amino acids that are usually referenced when building genetically coded proteins in all of life, and no other amino acids or are these only in humans and animals? I found the sentence below on this website and I wasn't sure what to make of it, is it true that there are...
  4. N

    Chemistry Estimating number of amino acids with protein molecular mass

    Homework Statement Suppose you were told you had a protein with molecular mass of 65,000 g/mol. Show how you would estimate the number of amino acids present in this protein. Keep in mind that you cannot calculate the exact number, the point of this is to approximate how many amino acids are...
  5. mktsgm

    Medical Essential Amino Acids: Do Our Bodies Produce Them?

    It is said that of the 20 amino acids that body needs to produce it's proteins, 9 are not made by the body, so they need to be given in the form food. My question is, is the said nine are not all produced by the body, or are the body produces them, albeit very little which is not enough?
  6. I

    Do amino-acids spontaneously bond within a cell?

    I was wondering whether it is possible for amino acids that end up in a cell (ready to be made into proteins) to spontaneously start to bond in the cytoplasm (or wherever the routing channel is I guess) and create randomly floating short strands of polymers? Furthermore, can it ever happen that...
  7. H

    Could Amino Acids Really Originate from Space?

    After having a debate with somebody about amino acids found in space, they replied, " As for the amino acids, we simply have no evidence that they can actually form in space -- it is indeed quite a ridiculous assertion. I am reminded of a PhD named Hugh Ross who actually talked about something...
  8. Daemach

    Right and left handed amino acids

    In nature, do right and left handed amino acids act like magnets in that right and left bind more readily than left + left or right + right? Do amino acids bind with each other, creating functional proteins without the help of other molecules/catalysts? At what temperatures/pressures does...
  9. F

    Are Amino Acids and Proteins the Same Thing?

    I got a question, consuming amino acid and consuming protein is the same thing right? Protein is a chain of amino acids but it does not really change their properties by becoming protein right?
  10. R

    What is the size of amino acids in nm or Angstroms?

    Just wondering what the physical size of amino acids such as glycine and alanine are in nm or Angstroms. Thanks.
  11. Greg Bernhardt

    Chemists learn more about how life started on earth?

    Chemists claim to have solved riddle of how life began on Earth http://phys.org/news/2015-03-chemists-riddle-life-began-earth.html Here is the journal article http://www.nature.com/nchem/journal/vaop/ncurrent/full/nchem.2202.html
  12. miles johnstone

    Basics for: Carbohydrates, Proteins, Amino Acids and Lipids

    I have been trying to get my head around the basics for these four (Carbohydrates, Proteins, Amino Acids and Lipids) for about a week and I just don't understand the basic structure, formulas and such. Help?!
  13. N

    Why amino acids as Zwitterons in solid state and ph neutral?

    Hi forum goersI'm reviewing some coursework for my General Chemistry class and cannot seem to find a reasonable explanation of why amino acids exist as zwitterons in solid state and ph7 solutions. I'm fairly certain the explanation has to do with its solubility in water, but I am not sure. Here...
  14. R

    Acidity and basicity in amino acids

    Hello! I'm having a hard time understanding the acidity and basicity of amino acids. I read this: the acidic group in an amino acid is NOT the -COOH but the NH3+ and the basic group is COO- and not the NH2... why? Thanks in advance!
  15. M

    PH, pKa, pI, and net charge of amino acids

    okay well basically this is what i know or think i know: i have the pKa's of the carboxyl, amino, and R group of the amino acid and the pH of the solution it is in. I'm supposed to figure out the net charge for it at different pHs. i taught myself one way to do it (by looking **** up) and i...
  16. M

    How many amino acids are in the hemoglobin of humans, gorillas, and horses?

    I'm doing a lab and my biology teacher specifically told me to count the amino acids found in the hemoglobin of the aforementioned animals. Since I'm sure I'm not the only one who'd rather not count, and I cannot for the life of me find the numbers on the Internet, I figured I would post what...
  17. J

    Understanding Amino Acid Acidity and Basicity in Reactions

    Homework Statement How does the following reaction demonstrate an amino acid as an acid: H2NCH2COOH + CH3OH → H2NCH2COOCH3 + H2O How does the following reaction demonstrate an amino acid as a base: H2NCH2COOH + CH3COCl → CH3CONHCH2COOH + HCl Homework Equations The Attempt at a...
  18. P

    3 Non-Chiral Amino Acids in Organisms

    hi, I've got a problem,which 3 amino acids are non-chiral ? I know there are many of them but I suppose they're only asking about those which are in organisms... I know about glycine but what are the other two ? thanks
  19. C

    Detection of Amino Acids and Nucleotide bases

    1. I need to detect amino acids and nucleotide bases that MAY be present in small quantities on Titan in the Hydrocarbon seas Homework Equations Not required this is for a mission analysis class The Attempt at a Solution So I'm working on a project for my fourth year class in...
  20. C

    Astrobiochemistry: Detection of Amino acids and nucleotide bases

    So I'm working on a project for my fourth year class in Space Mission Design and Analysis (I'm a fourth year space systems engineering student). My project is an astrobiology mission to Titan, Saturn's sixth moon, which is only slightly smaller than Mars with a atmosphere of Nitrogen of...
  21. J

    Why are there only 20 Amino Acids Found in Nature?

    We all know an amino acid consists of a carbon atom with an amine group, a carboxylic acid group, and a hydrogen atom. Also attached to this carbon is an 'R' group, which varies from amino acid to amino acid. My question regards the 'R' group. If the R group can be anything from a hydrogen...
  22. T

    Test for amino acids in Protein shakes (Experiment)

    I was wondering whether anyone knows an experiment relating to bodybuilding protein shakes. I want to find out which amino acids are present within the protein shake by doing an experiment but i have no clue what how to carry it out. The protein is in powder form. I was thinking of...
  23. K

    What is the relative size of amino acid R chains and how can it be determined?

    I need to compare amino acid R chains relative to each other. Is there a way to figure this out with the chemical forumula or am i supposed to glance over the stuctures? Also I am finding mixed messages about polarity for each. Are these correct? thanks lab test rf...
  24. K

    Estimating Volumes of Amino Acids in nm^3

    Homework Statement Estimate the volumes of the various amino acids in units of nm^3 Homework Equations V = 4/3*pi*r^3 The Attempt at a Solution Is it alright to treat the amino acids as spheres? Using this I was thinking of measuring the distance, atomic radii and bond length...
  25. S

    What Does 2-Amino-Propanol Formation Indicate About an Octapeptide's Structure?

    Homework Statement A small octapeptide was isolated. Amino acid analysis from 6N HCl hydrolysis indicated: 14 micromoles alanine, 17 micromoles ammonium, 15 micromoles valine, 16 micromoles arginine, 46 micromoles of isoleucine, 15 micromoles of glycine, 17 micromoles of aspartate...
  26. S

    Do essential amino acids undergo transamination reactions?

    Checked google no satifying answer.Thanks :smile:
  27. S

    How are non essential amino acids synthesized?

    Hello everyone, My biochemistry book just says there are 20 amino acids that are essential and not synthesizd by the body. Then it doesn't say how other amino acids are synthesized. My guess is they are synthesized from transamination reactions of essential amino acids. Does that mean if you...
  28. J

    Affect of adjacent amino acids on pKa values

    Hello, I use some standard tables of amino acids pKa values, as the one here: http://www.cem.msu.edu/~cem252/sp97/ch24/ch24aa.html and I am especially interested in the pKr (i.e. pKa of the side chains). Correct me if I'm wrong, but pKa values listed in such tables refer to a "free" peptide...
  29. M

    Illustrate Hydrogen Bonding: Amino Acids

    Homework Statement The following structures illustrate hydrogen bonding interactions between amino acid side chains and/or backbone atoms within a protein structure. In which of the following figures are the structures and hydrogen bonding completely correct? Homework Equations...
  30. W

    What mechanism is responsible for the sequencing of amino acids?

    Homework Statement What mechanism is responsible for the sequencing of amino acids? Homework Equations The Attempt at a Solution I don't quite understand, is it asking what is the procedure called that causes sequencing of amino acids?
  31. M

    Left Handed Amino Acids Discovered in 4.5x10^9 year old metorite

    http://www.sciencedaily.com/releases/2008/02/080228174823.htm This seems exciting for origin of life research.
  32. K

    Which of these methods can break ionic bonds between amino acids?

    i am doing revision for my exams aand was wondering which one of these, high temperature, hydrolysis or pH change would break the ionic bond between amino acids. I would go for pH change. I have no reason, it's just instinctively.
  33. J

    How Is the Acidity or Basicity of Amino Acids Determined?

    How can you tell if a given amino acid is acidic or basic? I'm lost here. My first thought would be to look at the pKa values. There is virtually no difference in the pKa values for the carboxyl groups; all range from 1.82-2.38. The same goes for the pKa values of the amino groups; all range...
  34. R

    Can Excessive Consumption of Amino Acids Lead to Disease?

    Is it okay to eat pure amino acids or can they cause disease?
  35. P

    Essential Amino Acids - Get Your Daily Requirements

    -------------------------------------------------------------------------------- Hi there When talking about limiting amino acids what does it really mean... What I think it means is say we have a food eg wheat it has all the essential amino acids (aa) in it except one of them is not...
  36. M

    Beta Amino Acids: Definition & Examples

    What is a beta amino acid and how would a beta amino acid look like? I know that the beta carbon is the second carbon from the functional group but which group would be where? Can I have an example of a beta amino acid?
  37. B

    Amino acids on their own vs in a polypeptide chain?

    Bio Help! what is the difference between amino acids on their own and amino acids that have been incorporated into a polypeptide chain? My answer is that amino acids on their on do nothing. However when they interact they create a protein which eventually takes on a particular function...
  38. Monique

    Donkey bridge to remember amino acids?

    lol, I hope that a donkey bridge is a used term in English? I'll explain it, just in case.. it is to make an associative link between things to be remembered. Is there any easy way to learn the structures of all the 20 aminoacids and whether they are polar/nonpolar/charged? It would be...