Polar Amino Acid & pK value – Biochemistry

Test 1 Polar Amino Acid & pK value – Biochemistry

In this chapter we discuss Polar Amino Acid & pK value Biochemistry.

Amino Acid


How many standard amino acids are there?

α-amino acids

Amino acids are known as what because of their primary nature?


which amino acid is called ‘α’ but actually secondary amino group?

carboxylic acid and α-amino group

the pK and pK2 refer to which groups on an amino acid respectively?

2.2 and 9.4

What are the average pK1 and pK2 values of the amino acids?

amino group and carboxylic acid group

physiological pH 7.4 means which group is protonated and which group is in its conjugate base form?

ionizable side group

pKR is the pK for what?


A molecule with opposite possible polarities are known as what?

condensation reaction and peptide bonds

what reaction type and name of the bond turns amino acids into polypeptides?

amino terminus

The end of a polypeptide with an amino group is called what?

carboxyl terminus

The end with a carboxylic acid group is called what?

length and amino acid sequence

protein variety is shaped by what two factors of a polypeptide chain?

glycine, alanine, valine, leucine, isoleucine, methionine, proline, phenylalanine, tryptophan

Which amino acids have non-polar side chains?


Alanine, valine, leucine, and isoleucine all have non-polar and what other property of side chains?


What does aliphatic mean?


Which amino acid has a thioether group?

pyrroline side group

Proline has what special structure?

phenyl group

Phenylalanine has which special side group?

indole group

tryptophan has which special group in its side chain?

Serine, threonine, asparagine, glutamine, tyrosine, cysteine

which amino acids have uncharged polar side chains?


one uncharged polar side chained amino acid can form disulphide bridges which?

Tyrosine, phenylalanine, tryptophan

which amino acids are aromatic?

lysine, arginine, histidine, aspartate, glutamate

which amino acids are charged polar side chains?


What is histidines’ pKR value?


As histidines pKR is within physiological pH what feature plays a reoccurring role in enzyme mechanism?


aspartic and glutamic acid have negatively charged side chains above which pH value?


asparaginine and glutamine are what of aspartic and glutamic acid?

protonation and therefore charge

Some amino acid has several ionizable groups what varies with pH of the substance that the amino acid is found in?

isoelectric point

for an amino acid group the pH at which their is no charge is called what with a equation 1/2(pKi+pKj)

K1 and K2

for monoamino, monocarboxylic acids Ki and Kj represent

K1 and KR

for aspartic and glutamic acid Ki and Kj represent what?

KR and K2

for arginine and histidine and lysine Ki and Kj are what?

3.5 to 4.0

pK values in an unfolded protein for α-carboxyl groups are what?


the pK values for unfolded protein carboxyl group are higher or lower then free amino acids?

7.5 to 8.5 and higher

what is the pK values for α-amino groups in proteins and is this higher or lower then free amino acids?

attracts electrons making deprotonation harder

pK values of an amino group in a protein are different because in free amino acids what does the carboxylate group do?


because of the easy variance of pK how are polypeptide pI normally determined?

-ine for -yl

when naming amino acid residues what suffix is dropped and what is it replaced with?


alanine in a polypeptide would be?

optically active and polarimeter

what property do all amino acids except glycine have and how is it measured?

chiral centre

you cannot superimpose an optically active molecule over its mirror image what type of centre must it have?


what property do optically active molecules have?


a chiral carbon must have four types of groups coming of it which are all what?


non-superimposable images are called what in relation to each others?

rotate plane polarized light, react with other enantiomers

what two ways are enantiomers detected from one another?

amount of rotation and absolute configuration

what can we not predict about and from plane polarized light respectively?


optical enantiomers will rotate plane polarized light by the same amount in degrees but in a different what?

L-α-amino acid or D-α-amino acid

the fischer convention determined a method of naming stereoisomers as levo or dextro an amino acid is either what?

L-amino acids

all amino acid residues are which configuration?

racemic mixture

a mixture with equal amount of one enantiomer as the other is what?

bacterial cell wall and resists petitdases

all L-α-amino acids reaction with L-amino acids same with D-amino acids where in nature are D-amino acids found and why?


D-amino acids aren’t synthesized by RNA, but enzymes in which microbes, do synthesize them?


thalidomide has biologically active enantiomers which means it can’t be used as a racemic mixture which drug doesn’t?

modifications to specific residues

after a polypeptide chain is synthesized what happens in the golgi apparatus?

hydroxylation, methylation, acetylation, carboxylation, phosphorylation

what basic forms of modification happens to the amino acid side chains?

dopamine and neurotransmitters

glycine and tyrosine can be modified to γ-aminobutryic acid and what to be used as what?

glutathione (Glu-Cys-Gly)

many small polypeptide are important for example?


many single amino acids are used to transport which atoms?


what molecule is the fischer convention based on?

chiral centre

the fischer convention imagines a molecule with only one what?

above and below the plane of the paper

In fischer projections horizontal bond extend where and vertical where?

carboxyl, R and amino, H

In an amino acid which two molecules are horizontal (above) and which vertical (below) respectively for fischer convention?

L stereochemical configuration

all amino acids derived from proteins have which configuration?

rotate plane polarized light

L and D configuration doesn’t indicate the individual amino acids ability to do what?