amino acids are what type of bonds
Functions of Proteins 3. Amino Acids Amino acids • are the molecular building blocks of proteins • contain a carboxylic acid group and an amino group on the alpha () carbon • are ionized in solution • each contain a different side group (R) side chain R │ H 2 N —C — COOH │ H 4. Cysteine is the sole amino acid whose side chain can form covalent bonds, yielding disulfide bridges with other cysteine side chains: --CH2- S-S -CH2-- . A disulfide bridge between cys201 in the model peptide and cys136 is shown here: . III. A model peptide of 12 amino acids (gly193-asn204) that spans the gamma chymotrypsin protein (at left) is used to illustrate example bonds in a known structure. The gamma chymotrypsin protein consists of four peptide chains (A, B, C, D), generated by cleavage of a precursor polypeptide. 4. Hydrogen bonds form between H of a polar R group and the O or N of another amino acid. For example, a hydrogen bond can form between the groups of two serines or between the of serine and the in the R group of glutamine. 5. Covalent bonds arise when two atoms share electrons. In addition to the covalent bonds that connect the atoms of a single amino acid and the covalent peptide bond that links amino acids in a protein chain, covalent bonds between cysteine side chains can be important determinants of protein structure. III. Electrostatic Interactions. A. Ionic Bonds-Salt Bridges Ionic bonds are formed as amino acids bearing opposite electrical charges are juxtaposed in the hydrophobic core of proteins. Ionic bonding in the interior is rare because most charged amino acids lie on the protein surface. Proteins are biological polymers composed of amino acids. Amino acids, linked together by peptide bonds, form a polypeptide chain. One or more polypeptide chains twisted into a 3-D shape form a protein. Proteins have complex shapes that include various folds, loops, and curves. R-group Hydrocarbon Neutral Acid or base where the COOH is understood to be the carboxyl group shown above. There are 20 amino acids which make up the proteins, distinguished by the R-group. The simplest of the amino acids, glycine, has just H as an R-group. Amino acids are the structural elements from which proteins are built. When amino acids bond to each other, it is done in the form of an amide, making a connection which is called a peptide linkage. This can be illustrated with the two simplest amino acids, glycine and alanine. Polar Amino Acids An amino acid is polar when the R group is an alcohol, thiol, or amide. 11. Acidic Amino Acids An amino acid is acidic when the R group is a carboxylic acid. 12. Basic Amino Acids An amino acid is basic when the R group is an amine. Peptide Bonds. The joining of amino acids in the process of making biochemical molecules like proteins is done by bonds which are referred to as peptide bonds. This may be illustrated with the two simplest amino acids, glycine and alanine.
Peptide bond