Biomolecules By : Aprajita Shankhdhar
Amino Acids General Amino Acid Structure Amino acids are organic compounds containing an amino group and an acidic group as substituents on the same carbon i.e., the -carbon. Hence, they are called -amino acids. They are substituted methanes acid group mino group OH There are four substituent groups occupying the four valency positions. These are hydrogen, carboxyl group, amino group and a variable group designated as R group Based on the nature of R group there are many amino acids radical group
However, those which occur in proteins are only of twenty types. The R group in these proteinaceous amino acids could be a hydrogen (the amino acid is called glycine), a methyl group (alanine), hydroxy methyl (serine), etc.
NON-POLAR +CHARGE H,N-C-C -C-C CH CH, CH, Valine (Val /V) CH2 CH2 CH CH, NH, CH CH2 NH C = NH,' NHz Glycine (Gly G) Cysteine (Cys/C) Alanine Proline (Ala A) (Pro /P) Arginine Lysine (Lys K) Arg /R) CH H,C-CH O CH CH, CH, Leucine (Leu /L) Isoleucine Methionine Tryptophan Phenylalanine Histidine (MetM) Trp/W) (Phe / F) (His / H) POLAR -CHARGE CH2 CH CH2 CH OH CH Threonine (Thr IT) NH2 Asparagine (Asn /N) NH, o Glutamine (Gin Q) Serine Tyrosine (Tyr IY) Aspartic Acid (Asp/D) Glutamic Acid (Glu /E) (Ser S)
.The chemical and physical properties of amino acids are essentially of the amino, carboxyl and the R functional groups .Based on number of amino and carboxyl groups, there are acidic (e.g., glutamic acid), basic (lysine) and neutral (valine) amino acids Similarly, there are aromatic amino acids (tyrosine, phenylalanine, tryptophan). A particular property of amino acids is the ionizable nature of -NH2 and -COOH groups. Hence in solutions of different pHs, the structure of amino acids changes.
cation zwitterion anion NH3 NH3 pk. pK, NH2 O pK2 COO low pH pH high pH
Lipids are generally water insoluble. .A fatty acid has a carboxyl group attached to an R group. The R .could be a methyl (-CH3), or ethyl (-C2H5) or higher number of . For example, palmitic acid has 16 carbons including carboxyl They could be simple fatty acids. group CH2 groups (1 carbon to 19 carbons) carbon. Arachidonic acid has 20 carbon atoms including the carboxyl carbon. Fatty acids could be saturated (without double bond) or unsaturated (with one or more C-C double bonds) Palmitic Acid
Fatty Acid Structure Unsaturated fatty acid Carboxyl group Omega H I nd Saturated fatty acid end Hydrocarbon chain
Another simple lipid is glycerol which is trihydroxy propane. Many lipids have both glycerol and fatty acids. then monoglycerides, diglycerides and triglycerides. These are also called fats and oils based on melting point. . Here the fatty acids are found esterified with glycerol. They can be Oils have lower melting point (e.g., gingely oil) and hence remain as oil in winters. phosphorous and a phosphorylated organic compound in them. is one example. Some tissues especially the neural tissues have . Can you identify a fat from the market? Some lipids have . These are phospholipids. They are found in cell membrane. Lecithin lipids with more complex structures
Living organisms have a number of carbon compounds in which heterocyclic rings can be found. . Some of these are nitrogen bases - adenine, guanine, cytosine, uracil, and thymine. When found attached to a sugar, they are called nucleosides. If a phosphate group is also found esterified to the sugar they are called nucleotides. Adenosine, guanosine, thymidine, uridine and cytidine are nucleosides. . Adenylic acid, thymidylic acid, guanylic acid, uridylic acid and cytidylic acid are nucleotides. Nucleic acids like DNA and RNA consist of nucleotides only DNA and RNA function as genetic material.
Acidic amino acid have more Carboxyl group than amino group Ex:Gultamic acid Basic amino acid have more amino group than Carboxyl group. Ex: histadine
CH2-O-C-R 1 CH OH CH2- OH CH2-O-C-R 1 CH O-C-R 2 CH2-OH - - -R 1 CH O-C-R 2 CH2-O-C-R 3 monoglyceride diglyceride triglyceride
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