Test 1 Polar Amino Acid & pK value – Biochemistry
In this chapter we discuss Polar Amino Acid & pK value Biochemistry.
How many standard amino acids are there?
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?
The end of a polypeptide with an amino group is called what?
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?
Phenylalanine has which special side 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?
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?
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?
all amino acid residues are which configuration?
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?
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?
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?