hello everyone I'm Dr trupti and with this video I going to start a video lecture series on amino acids chemistry and Metabolism at the end of this video student shall be able to describe general structure of amino acids classify amino acids with suitable examples and explain the significance of amino acids amino acids are the structural units of proteins so protein are nothing but linear Polymers of L Alpha amino acids which are linked together by calent peptide bond so we need to understand what are amino acids what are alpha amino acids and what are L Alpha amino acids this is the general structure of amino acid amino acid means it has amino group and this amino acid is made up of two functional group in addition to this Amo group there is one more functional group that is carox group and both these group they are attached to the same carbon and this carbon is Alpha carbon because it is attached to four different types of groups to it means addition in addition to this Amo group as well as carboxilic group hydrogen atom and side chain R is also attached to this same carbon atom and why they are called as Alpha amino acid because both Amo group and carboxilic group they are attached to same Alpha carbon atom and that's why amino acid AIDS are called as Alpha amino acids now this R chain it it is a side chain and amino acids differ from each other in their side chains only which vary in structure size and charge the side chains are relatively small ranging from a single hydrogen to nine carbons now we will understand what is mean by L Alpha Amo acids amino acids usually exist in the ionic state in the body this is the structure of amino acid at physiological pH the amino group is in the protonated state and carboxilic group is in the deprotonated state this is Alpha carbon atom which is attached to four different groups one is amino group second carboxilic group third is hydrogen atom and fourth is r that is side chain now this since this Alpha carbon is attached to four different groups this carbon it acts as a chyal center and exhibit two different spatial configuration which are optically active and mirror images of each other and they are called as enantiomers and the isomerism is called as Optical isomerism and there are two types of amino acid L amino acids and D amino acid the structure of D and L amino acids they are based on configuration of D and L glycer alide so for example in case of L glyceride deide the hydroxy group is present on the left side in D glyceride hydroxy group is present on the right side likewise in L amino acid the amino group is present on the left side and in in case of deamino acid amino group is present on the right side it is the L amino acids which occur naturally in all biological proteins and that's why proteins are polymers of L Alpha amino acids but there are two free d amino acids dcene and D aspartic acid which have been found to be present in the brain tissues let's understand the numbering of carbon atoms in amino acid this is the structure of amino acid lysin and this amino acid it has this carbon atom which is Alpha carbon atom which is attached to four different groups Amo group carboxilic Group H and side chain so this is the alpha carbon the next carbon is beta then Gamma Delta and Epsilon so this Epsilon carbon atom second amino group is attached so the carbon numbering 1 2 3 4 starts from this carbon of this carboxy group so carboxy group carbon is number one alpha carbon is number 2 carbon beta carbon is three gamma carbon is fourth carbon Delta carbon is Fifth and Epsilon carbon is carbon number six in the amino acid lysin amino acids are of two types standard amino acid and non-standard amino acid so what is mean by standard amino acid standard amino acids are 20 in number because although there are 300 amino acids which occur in nature all proteins are made up of just 20 amino acids in varying combin ation so at the time of protein biosynthesis only these 20 amino acids are incorporated into a protein and that's why they are known as standard amino acids this is because only this 20 amino acid possess the genetic code which specifies the composition and size of a protein in addition to this 20 amino acid two more are there 21 selenocystine is called as 21st amino acid and pyin is 22nd amino acid now what are non-standard amino acid so in addition to the standard 20 amino acids which are Incorporated during protein synthesis few other amino acids are also seen in the biological system and they are called as non-standard amino acids and these non-standard amino acids though they are not incorporated into structure of protein at the time of protein biosynthesis but they play several biological important functions in the body and they include D amino acids nonprotein amino acids and various amino acid derivatives we will see this non-standard amino acid in separate video amino acids can be classified in four different ways the first classification is based on structure and chemical nature of amino acids second classification is based on polarity or solubility third classification is B based on the metabolic fate of amino acid and fourth classification is based on nutritional requirement and first type of classification which is based on structure and chemical nature again it is classified in different subgroups like seven subgroups the first one is amino acid containing aliphatic side chain second with a side chain containing hydroxy group third one with the side chain containing sulfur that is sulfur containing amino acid fourth one Having side chain with acidic group that is acidic amino acids and their amides fifth one is side chain with basic groups which constitute basic amino acids sixth one is aromatic amino acid and seventh is amino acids based on the polarity it has two different types of amino acids hydrophilic which are polar in nature which are soluble and hydrophobic which are non-polar which is which are insoluble based on the metabolic fate they can be glycogenic ketogenic or both glycogenic and ketogenic based on the nutritional requirement they can be essential non-essential or semi- essential now let's start with the first way of classifying amino acid which is based on structure and chemical nature and first group of this classification that is structural classification is amino acids with aliphatic side chain there are five amino acids in this group that is glycine alanine valine Lucine and isoline which can be remembered as a pneumonic GOI G A vli the amino acid glycine is abbreviated as three letter symbol g l y and one letter symbol G alenin by Al a and and a valine by v l and one letter symbol V Lucine by l e u and L and isoline by I and I this is the structure of glycine so see this structure is is Alpha carbon atom present in this structure of amino acid glycine no because this carbon atom is not attached to four different groups because side chain only contains hydrogen atom and that's why this glycine is a amino acid which doesn't have chyal Center so it does not exhibit stereoisomerism and that's why it is optically inactive this is the structure of alanin which has methyl group in the side chain structure of valin structure of Lucine and this is the structure of isoline so glycine is the simplest amino acid which is optically inactive and as it has no chyal Center valin Lucine and isoline they have branches in their side chains and that's why they are called as Branch chain amino acids second group in structural classification is the amino acids Having side chain with hydroxy that is O group and the examples are Serene in the structure of serene hydroxy group is attached here so this is the hydroxy group containing amino acid second is thionin which has hydroxy group in its side chain thyrosin can also be included in this classification of amino acid Having side chain with hydroxy group as the hydroxy group is present in its structure so the amino acids which have side chain containing hydroxy group are serin thionine and thyrosin in structural classification third group is of amino acid Having side chain with sulfur atoms and the examples are cysteine cysteine has sulf dril Group which is also called as mapto group in its side chain and methionin methionine has a sulfur atom in its structure and this is called a thioether group so these are cysteine and methionine these are sulfur containing amino acids this is the structure of ctin cysteine is a condensation product of two molecules of cysteine linked through a dulfi bridge and this ctin contributes extensively to higher levels of structural organization of protein fourth group amino acids are having side chain with acidic group or their amides and they are called as acidic amino acids the examples are aspartic acid aspartic acid is denoted by three letter symbol ASP and one letter symbol D so in the structure of aspartic acid the carbon oxic group is attached to Beta carbon this is Alpha carbon and this is beta carbon so the second carboxilic group is attached here it is di carboxilic monoamino acid aspar is a amide of aspartic acid glutamic acid in the glutamic acid the second carboxilic group is attached to gamma carbon atom this alpha beta and gamma so this is gamma carboxilic group containing amino acid this is a glutamic acid this is glutamine which is amide of glutamic acid so there are four examples of amino acids having acidic groups in their structure and their amides and the these aspartic acid and glutamic acid they are called as di carboxilic mono amino acid because they contain two carboxilic group in their structure and one amino group the fifth group is amino acid with side chain having basic groups in their structure they are called as basic amino acid they are dibasic monoc carboxilic acid because they have two amino group and one carboxilic group in their structure and the examples are Arginine Arginine has gonino group in its structure lysine it has Epsilon amino group because the second amino group is attached to this Epsilon carbon and hisin the Hine has imidazol group in its structure so there are three basic amino acids arginine lysine and and histadine the sixth group is aromatic amino acids and it contains aromatic ring in its structure which absorb ultraviolet light at 280 nanometer and the examples are Phil alanin which is denoted by one L symbol F and it has Benzene or final ring in its structure second is thyrosin which is denoted by one letter symbol T and it has phenol ring in its structure and as this phenol ring has hydroxy group it is also included in the amino acid having hydroxy group the third amino acid is tryptophan which is denoted by W and in its structure it has indol group the seventh group is amino acid and this amino acid contains only one amino acid that is Proline because it does not contain amino group it contains amino group second way of classification of amino acid is based on Polar that is solubility so they can be polar or non-polar polar are hydrophilic which are water loving and non-polar are hydrophobic amino acid which are water heating amino acids the examples of hydrophilic amino acids which are polar in nature they can be negatively charged they can be positively charged or uncharged the amino acids which are negatively charged and polar in nature they are acidic amino acid aspartic acid and glutamic acid these are negatively charged polar amino acids lysine aine histadine these are basic amino acids which are positively charged and polar in nature the uncharged amino acids are also polar which are Serene thionine thyrosine espine glutamine cysteine and glycine the hydrophobic amino acids are aliphatic in nature and examples are alanine valine Lucine and isol ucing the aromatic amino acid pH alenin and tryptophan they are non-polar in nature and Proline and methionine they are also hydrophobic third type of classification is based on metabolic fate means the carbon skeleton of some amino acid is involved in the synthesis of glucose in the synthesis of lipids So based on their metabolic fate they are further classified as both glucogenic and ketogenic so carbon skeleton of these four amino acid is involved in the synthesis of both glucose and lipids and the examples are felinine isoline tryptophan and thyrosin pit p i t t so there are four amino acids which are both glucogenic and ketogenic there are two amino acids which are said to be ketogenic they are involved in the synthesis of lipids their carbon skeleton is involved in the synthesis of lipid out of this two Lucin is considered as exclusive ketogenic some authors consider lysin also as ketogenic but the exclusively ketogenic amino acid is Lucine the rest 14 amino acids they are glucogenic for example alanin aspartate Glycine and methionin so you have to remember four amino acid which are both glucogenic and ketogenic that is pit Phil alanin isoline tyrosin and tryptophan Lucine is exclusively ketogenic and rest others you can put into the group of glucogenic Fourth Way of classification is based on nutritional requirement and as per the nutritional requirement there are 10 essential amino acids these essential amino acids cannot be synthesized by the body and hence they need to be supplied through diet so there are 10 amino acids which are essential and which can be remembered as pneumonic private team Hall which stands for Phil alanin Val and tryptophan for private theme thionine isoline and methionin Hall histadine Arginine Lucine and lysine so you need to remember this 10 essential amino acids in vaa most of the time examiner ask this question name 10 essential amino acids and it can also come in theory exam as well there are two semi- essential amino acids these are histadine and Arginine and are not synthesized during infancy but can be partly made by adult body and hence they are referred as semi- essential amino acids Arginine and histadine synthesize in the body are sufficient for normal adults but they become inadequate during the growing years that is in case of infants and children pregnancy and uh lactation and this is the reason they are considered to be semiessential or conditionally essential and rest others are nonessential which are synthesized in the body and the examples are glycine alanine Serene cysteine aspartate asparagin glutamate glutamine thyrosin and Proline selenos sytin is the 21st amino acid which is denoted by three L symbol S C and one letter symbol U the structure of selenos and cine is similar only difference is that in cine sulfur is present and in the selenos system selenium is present this selenos system is encoded by code UG and it is integral component of various enzymes like gluton peroxidase deiodinase glycin reductase and tho redoxin reductase pyin is 22nd amino acid it is coded by a stop Cod on UAG it is similar to lysin but with added pyin ring link to end of lysin side chain and this pyro liin this amino acid is the constituent of methyl transference enzyme from a methane producing bacteria what is the significance of amino acids amino acids are involved in the synthesis of various biologically important compounds for example thyrosin is amino acid which is involved in the synthesis of hormone thyroxine melanin epinephrine norepinephrine and do a glutamic acid is involved in the synthesis of neurotransmitter Gaba tryptophan is involved in the synthesis of nasin and serotonin glycine Arginine methionin it is involved in the synthesis of creatin gam gam gam for creatine Glycine and cystin involved in the synthesis of bile salts glycine is involved in the synthesis of he glutamic and aspartic acid are required for pyramidan based synthesis various purine bases are also synthesized from glycine glutamic acid and aspartic acid co-enzyme a is synthesized from beta alanin and histamine is synthesized from histadine various disorders are associated with amino acid metabolism which we are going to study in videos on amino acid metabolism so the disorders like Phil ketonuria tyrosinemia albinism alcaptonuria homocystinuria foch chromosoma carcinoid syndrome and heart NB disease these are some of the disorders of related to amino acid metabolism let's summarize the topic amino acids amino acid topic is very important for short answer question as well as vaa amino acid has amino group in its structure both both amino group and carboxilic group is attached to the alpha carbon and that's why amino acids are alpha amino acid as amino group is present on the left side it is called as L Alpha amino acid and in human proteins are made up of L Alpha amino acids now these amino acids are based classified in four ways based on the structure and chemical nature they are classified as aliphatic Amo acid like glycine alanine valine Lucine and isoline G hydroxy group containing amino acid serin thionine sulfur containing amino acid ctin methionin acidic amino acid and their amides like aspartic acid aspin glutamic acid glutamine Hine Arginine and lysine these are basic amino acid pH alanine tyrosin tryptophan they are aromatic amino acid and Proline is amino acid based on the polarity that is solu in water they are polar and non-polar mostly acidic basic amino acid they are polar in nature aliphatic and aromatic amino acid they are non-polar in nature based on the metabolic fate where the carbon skeleton of this amino acid is involved in the synthesis of glucose or lipid based on that they are again classified as glucogenic ketogenic if they are involved in the synthesis of only lipids and both means they are involved in the synthesis of both glucose as well as lipid so there are three there are four amino acid pH alanine isoline thyrosin and tryptophan these amino acids are both glucogenic and ketogenic Lucine is exclusively ketogenic and rest other are glucogenic Fourth Way of classification is nutritional classification and there are three ways of classifying amino acid based on the requirement essential amino acids are not synthesized in the body they have they have to be provided in the diet non-essential are synthesized semi essential are conditionally essential and essential amino acids are 10 in number and they can be remembered by pneumonic private team Hall phenin valin tryptophan thionine isoline methionin histidine Arginine Lucine and lysine hisin and Arginine are also semi-essential amino acids if you find this video useful Please Subscribe like and share and thank you for watching