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20 Amino Acids Structures And Names Pdf

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Here is the easy way to remember the all 20 amino acid. These 20 amino acids are called protein amino acids or standard amino acids or magic

Amino acid

All of the proteins on the face of the earth are made up of the same 20 amino acids. Linked together in long chains called polypeptides, amino acids are the building blocks for the vast assortment of proteins found in all living cells.

All amino acids have the same basic structure, which is shown in Figure 2. With the exception of glycine, which has an R-group consisting of a hydrogen atom, all of the amino acids in proteins have four different groups attached to them and consequently can exist in two mirror image forms, L and D.

With only very minor exceptions, every amino acid found in cells and in proteins is in the L configuration. There are 22 amino acids that are found in proteins and of these, only 20 are specified by the universal genetic code.

The others, selenocysteine and pyrrolysine use tRNAs that are able to base pair with stop codons in the mRNA during translation.

When this happens, these unusual amino acids can be incorporated into proteins. Enzymes containing selenocysteine, for example, include glutathione peroxidases, tetraiodothyronine 5' deiodinases, thioredoxin reductases, formate dehydrogenases, glycine reductases, and selenophosphate synthetase.

Pyrrolysine-containing proteins are much rarer and are mostly confined to archaea. This classification of amino acids has little to do with the structure of amino acids. Essential amino acids vary considerable from one organism to another and even differ in humans, depending on whether they are adults or children.

Table 2. Some amino acids that are normally nonessential, may need to be obtained from the diet in certain cases. Individuals who do not synthesize sufficient amounts of arginine, cysteine, glutamine, proline, selenocysteine, serine, and tyrosine, due to illness, for example, may need dietary supplements containing these amino acids. Common ones include ornithine and citrulline.

Both of these compounds are intermediates in the urea cycle. Ornithine is a metabolic precursor of arginine and citrulline can be produced by the breakdown of arginine.

The latter reaction produces nitric oxide, an important signaling molecule. Citrulline is the metabolic byproduct. It is sometimes used as a dietary supplement to reduce muscle fatigue. We separate the amino acids into categories based on the chemistry of their R-groups.

If you compare groupings of amino acids in different textbooks, you will see different names for the categories and sometimes the same amino acid being categorized differently by different authors. Indeed, we categorize tyrosine both as an aromatic amino acid and as a hydroxyl amino acid. It is useful to classify amino acids based on their R-groups, because it is these side chains that give each amino acid its characteristic properties.

Thus, amino acids with chemically similar side groups can be expected to function in similar ways, for example, during protein folding. For example, the R-group carboxyl found in aspartic acid has a pKa value of 3. When these are bound in a peptide bond, they no longer ionize. Some, but not all amino acids have R-groups that can ionize.

Most proteins have relatively narrow ranges of optimal activity that typically correspond to the environments in which they are found Figure 2. Not all amino acids in a cell are found in proteins. The most common examples include ornithine arginine metabolism , citrulline urea cycle , and carnitine Figure 2.

When fatty acids destined for oxidation are moved into the mitochondrion for that purpose, they travel across the inner membrane attached to carnitine. Of the two stereoisomeric forms, the L form is the active one. The molecule is synthesized in the liver from lysine and methionine. From exogenous sources, fatty acids must be activated upon entry into the cytoplasm by being joined to coenzyme A.

The CoA portion of the molecule is replaced by carnitine in the intermembrane space of the mitochondrion in a reaction catalyzed by carnitine acyltransferase I. The resulting acylcarnitine molecule is transferred across the inner mitochondrial membrane by the carnitineacylcarnitine translocase and then in the matrix of the mitochondrion, carnitine acyltransferase II replaces the carnitine with coenzyme A Figure 6. We categorize amino acids as essential or non-essential based on whether or not an organism can synthesize them.

All of the amino acids, however, can be broken down by all organisms. They are, in fact, a source of energy for cells, particularly during times of starvation or for people on diets containing very low amounts of carbohydrate. From a perspective of breakdown catabolism , amino acids are categorized as glucogenic if they produce intermediates that can be made into glucose or ketogenic if their intermediates are made into acetyl-CoA.

Figure 2. Note that some amino acids are both glucogenic and ketogenic. After a protein is synthesized, amino acid side chains within it can be chemically modified, giving rise to more diversity of structure and function Figure 2. Common alterations include phosphorylation of hydroxyl groups of serine, threonine, or tyrosine.

Lysine, proline, and histidine can have hydroxyls added to amines in their R-groups. Other modifications to amino acids in proteins include addition of fatty acids myristic acid or palmitic acid , isoprenoid groups, acetyl groups, methyl groups, iodine, carboxyl groups, or sulfates.

In addition, N-linked- and O-linkedglycoproteins have carbohydrates covalently attached to side chains of asparagine and threonine or serine, respectively. Some amino acids are precursors of important compounds in the body. Examples include epinephrine, thyroid hormones, Ldopa, and dopamine all from tyrosine , serotonin from tryptophan , and histamine from histidine. Although amino acids serve other functions in cells, their most important role is as constituents of proteins.

Proteins, as we noted earlier, are polymers of amino acids. Amino acids are linked to each other by peptide bonds, in which the carboxyl group of one amino acid is joined to the amino group of the next, with the loss of a molecule of water.

Additional amino acids are added in the same way, by formation of peptide bonds between the free carboxyl on the end of the growing chain and the amino group of the next amino acid in the sequence.

The end of the peptide that has a free amino group is called the N-terminus for NH2 , while the end with the free carboxyl is termed the C-terminus for carboxyl. The folding of polypeptides into their functional forms is the topic of the next section. R-group chemistry Table 2. A D-form of the amino acid is also found in bacterial cell walls. Alanine is non-essential, being readily synthesized from pyruvate. As a result, glycine is the only amino acid that is not chiral.

Its small side chain allows it to readily fit into both hydrophobic and hydrophilic environments. It is nonessential to humans. It has a hydrophobic side chain and is also chiral in its side chain. Leucine is the only dietary amino acid reported to directly stimulate protein synthesis in muscle, but caution is in order, as 1 there are conflicting studies and 2 leucine toxicity is dangerous, resulting in "the four D's": diarrhea, dermatitis, dementia and death. Methionine is non-polar and encoded solely by the AUG codon.

In prokaryotic cells, the first methionine in a protein is formylated. It is the least flexible of the protein amino acids and thus gives conformational rigidity when present in a protein. Proline hydroxylation of hypoxia-inducible factor HIF serves as a sensor of oxygen levels and targets HIF for destruction when oxygen is plentiful.

It is noteworthy in hemoglobin, for when it replaces glutamic acid at position number six, it causes hemoglobin to aggregate abnormally under low oxygen conditions, resulting in sickle cell disease. It is readily produced by transamination of oxaloacetate. With a pKa of 3. Premature infants cannot synthesize arginine. In addition, surgical trauma, sepsis, and burns increase demand for arginine. Most people, however, do not need arginine supplements.

It is an essential amino acid in humans and other mammals. With a side chain pKa of 6, it can easily have its charge changed by a slight change in pH. Protonation of the ring results in two NH structures which can be drawn as two equally important resonant structures. It can also be ubiquitinated, sumoylated, neddylated, biotinylated, carboxylated, and pupylated, and.

O-Glycosylation of hydroxylysine is used to flag proteins for export from the cell. Lysine is often added to animal feed because it is a limiting amino acid and is necessary for optimizing growth of pigs and chickens. Aromatic amino acids Figure 2. It is a metabolic precursor of tyrosine. Inability to metabolize phenylalanine arises from the genetic disorder known as phenylketonuria.

Phenylalanine is a component of the aspartame artificial sweetener. It is a metabolic precursor of serotonin, niacin, and in plants the auxin phytohormone. Though reputed to serve as a sleep aid, there are no clear research results indicating this. It is a target for phosphorylation in proteins by tyrosine protein kinases and plays a role in signaling processes. In dopaminergic cells of the brain, tyrosine hydroxylase converts tyrosine to l-dopa, an immediate precursor of dopamine.

Dopamine, in turn, is a precursor of norepinephrine and epinephrine. Tyrosine is also a precursor of thyroid hormones and melanin. Being able to hydrogen bond with water, it is classified as a polar amino acid.

It is not essential for humans. Serine is precursor of many important cellular compounds, including purines, pyrimidines, sphingolipids, folate, and of the amino acids glycine, cysteine, and tryptophan. The hydroxyl group of serine in proteins is a target for phosphorylation by certain protein kinases.

Serine is also a part of the catalytic triad of serine proteases. It is one of three amino acids bearing a hydroxyl group serine and tyrosine are the others and, as such, is a target for phosphorylation in proteins. It is also a target for Oglycosylation of proteins. Threonine proteases use the hydroxyl group of the amino acid in their catalysis and it is a precursor in one biosynthetic pathway for making glycine.

The Twenty Amino Acids

Although there are hundreds of amino acids found in nature, proteins are constructed from a set of 20 amino acids. Generally, amino acids have the following structural properties:. All amino acids have the alpha carbon bonded to a hydrogen atom, carboxyl group, and amino group. The "R" group varies among amino acids and determines the differences between these protein monomers. The amino acid sequence of a protein is determined by the information found in the cellular genetic code. These gene codes not only determine the order of amino acids in a protein, but they also determine a protein's structure and function. Amino acids can be classified into four general groups based on the properties of the "R" group in each amino acid.

Amino Acids Reference Charts

Amino acids, often referred to as the building blocks of proteins, are compounds that play many critical roles in your body. Some may also be taken in supplement form for a natural way to boost athletic performance or improve mood. This article tells you everything you need to know about essential amino acids, including how they function, possible food sources and the benefits of taking a supplement. Amino acids are organic compounds composed of nitrogen, carbon, hydrogen and oxygen, along with a variable side chain group.

For details on it including licensing , click here. This book is licensed under a Creative Commons by-nc-sa 3. See the license for more details, but that basically means you can share this book as long as you credit the author but see below , don't make money from it, and do make it available to everyone else under the same terms. This content was accessible as of December 29, , and it was downloaded then by Andy Schmitz in an effort to preserve the availability of this book.

Hydrophobic - aliphatic Hydrophobic - aromatic Neutral - polar side chains Acidic. Amino acids are the compounds or building blocks that make up peptides and proteins. Each amino acid is structured from an amino group and a carboxyl group bound to a tetrahedral carbon.

IMGT Aide-mémoire

Basic Structure of Amino Acids. Introduction Essential amino acids Why learn this? Amino acids play central roles both as building blocks of proteins and as intermediates in metabolism. The 20 amino acids that are found within proteins convey a vast array of chemical versatility. The precise amino acid content, and the sequence of those amino acids, of a specific protein, is determined by the sequence of the bases in the gene that encodes that protein.

We've updated our Privacy Policy to make it clearer how we use your personal data. We use cookies to provide you with a better experience, read our Cookie Policy. Amino acids are the building blocks that form polypeptides and ultimately proteins. Consequently, they are fundamental components of our bodies and vital for physiological functions such as protein synthesis, tissue repair and nutrient absorption. Here we take a closer look at amino acid properties, how they are used in the body and where they come from.

Amino acids are organic compounds that contain amino —NH 2 and carboxyl —COOH functional groups , along with a side chain R group specific to each amino acid. About naturally occurring amino acids are known as of though only 20 appear in the genetic code and can be classified in many ways. In the form of proteins , amino acid residues form the second-largest component water is the largest of human muscles and other tissues. In biochemistry , amino acids which have the amine group attached to the alpha- carbon atom next to the carboxyl group have particular importance. They include the 22 proteinogenic "protein-building" amino acids, [6] [7] [8] which combine into peptide chains "polypeptides" to form the building blocks of a vast array of proteins. Twenty of the proteinogenic amino acids are encoded directly by triplet codons in the genetic code and are known as "standard" amino acids.


In this work, the known bond lengths for amino acids and the peptide bond are similarly shown to be atomic structures were presented for the first time. [13] ikafisipundip.org​pdf Fig. 4. Conventional molecular structures [15] of the “20” essential amino acids.


20 amino acids structures and names pdf files

All of the proteins on the face of the earth are made up of the same 20 amino acids. Linked together in long chains called polypeptides, amino acids are the building blocks for the vast assortment of proteins found in all living cells. All amino acids have the same basic structure, which is shown in Figure 2.

Chemically speaking, an amino acid is a carboxylic acid which has an amine group attached to it. The general formula of an amino acid is composed by a carbon alpha atom, a carboxyl group, a side chain group and an amino group. Amino acids IMGT classes of the 20 common amino acids Amino acid abbreviations, characteristics, volume and hydropathy index Charge, hydrogen donor and acceptor atoms, and polarity of the amino acid side chains.

Essential Amino Acids: Definition, Benefits and Food Sources

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Amino Acids: Structure, Groups and Function

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