Biochem Amino Acids and Proteins

what percentage of body mass is comprised of protein

14-16%

name some functions of protein in the body

• enzymatic catalysis

• transport

• storage

• structure

• motility

• division

• differentiation

describe enantiomers

• molecules that have the same chemical composition and bonds, just different configurations

in humans, all aas in proteins are

L-stereoisomers

describe the hydropathy index for amino acids

• measure of the hydrophobic character of an amino acid

• has a spectrum ranging from hydrophobicity to hydrophilicity

• a measure of polarity of an amino acid residue

the larger a number is on the hydropathy index ____

the more hydroPHOBIC an amino acid is

what makes proline special compared to other amino acids

• proline has a unique cyclic side chain that reduces the structural flexibility of polypeptide regions

• causes kinks

describe branched-chain amino acids (BCAAs)

• made of leucine, isoleucine, and valine

• could possibly increase muscle mass

why are amino acids with polar, uncharged R groups more soluble in water than nonpolar amino acids

• amino acids with polar R groups can form hydrogen bonds

describe how amino acids with aromatic R groups can participate in HYDROPHOBIC interactions

• aromatic side chains are nonpolar, making them hydrophobic

• (the hydroxyl group of Tyrosine can form hydrogen bonds)

which amino acids are positive at a Ph of 7.4

• lysine (K)

• arginine (R)

• histidine (H)

*these amino acids are HYDROPHILIC due to their charged R groups

what makes histidine different from other amino acids

• histidine has an ionizable imidazole functional group

• the imidazole allows the histidine to participate in enzyme catalyzed reactions

name 2 amino acids that are negative at pH 7.0

• aspartate (D)

• glutamate (E)

*These amino acids are hydrophilic

describe zwitterions

• molecules that have both a positive and negative charge

• predominates at a neutral pH

• can act as an acid (proton donor) and a base (proton acceptor)

describe pka

• acid dissociation constant

• measures the tendency of a group to give up protons

describe the isoelectric point

• the pH in which a molecule’s net charge is 0

• usually between 2 pka’s for an amino acid with no ionizable side chain

• appears in the middle of a vertical line in a titration chart

how can you find the isoelectric point of an amino acid with no ionizable side chains

• average the 2 pka’s of the amino acid