BIOCHEM - amino acids Flashcards
what is luciferase?
an enzyme that catalyses the production fo light from protein luciferin and ATP in fireflies
what are essential amino acids?
amino acids which cant be syntesised by the body
how many essentail aa’s are there?
9
draw general structure of an amino acid
what is the carbon at the centre of the aa called?
alpha carbon (Ca)
what s a steroisomer?
- Isomers are molecules which have the same
chemical formula but different chemical structures.
what is an enantiomer?
stereoisomers which are
mirror images of each other but cannot be
superimposed on each other.
what is the main type of amino acid in humans, L or D?
L
where are d amino acids found?
in peptides of
bacterial cell walls and
certain antibiotics
what are the classes of amino acids?
- Non-polar, aliphatic R groups
- Aromatic R groups
- Polar, uncharged R groups
- Positively charged R groups
- Negatively charged R groups
how are amino acids classified?
based on their
side chains (R groups)
properties of nonpolar, aliphatic r groups
- Aliphatic R groups have linear chains of carbon atoms.
- Do not accept or donate H+ ions.
- Do not form hydrogen or ionic bonds.
- They are hydrophobic
mnemonic for non polar, aliphatic amino acids? + what are they
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isoleucine
leucine
glycine
alanine
proline
valine
methionine
what is significant about proline?
it is an imino acid (not amino)
it has a ring structure which makes the proteins containing it very rigid, non flexible - collagen
what are the aromatic amino acids?
WYF
tryptophan , tyrosine, phenylalanine
why can proteins which contain aromatic aa’s absorb light? what frequncy can they absorb?
tryptohpan and tyrosine absorb UV light at 280 nm
why are tyrosine and tryptophan more polar than phenylalanine
tryptophan - has an N indole ring
tyrosine - has an OH group
whihc of the aromatic aa’s is least polar?
phenylalanine
what are the polar, uncharged amino acids?
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serine, threonine, cysteine, asparagine, glutamine
what modifications can be made to polar, uncharged aa’s?
- Serine and threonine can be phosphorylated at their hydroxyl (OH) group.
- Asparagine can have an oligosaccharide group attach to its amide group (N-glycosylation).
- Serine and threonine can have an oligosaccharide group attach to their oxygen
atom (O-glycosylation).
what is significant about the bonding properties of cysteine?
sulfhydryl group - can from disulphide bonds
important for protein structure
strongly hydrophobic
what are the positively charged AA’s?
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arginine, lysine, histidine
why is histidine weakly basic?
imidazole ring
do positively charged R groups have acidic or basic side chains?
basic
do negatively charged R groups have acidic or basic side chains?
acidic
what are the acidic AA’s?
glutamiae, aspartate
what are uncommon amino acids?
amino acids that have been modified from common amino acids after they have been incorporated into a polypeptide.
give examples of uncommon amino acids. where are these found?
4-hydroxyproline and 5-hydroxylysine
collagen
creatine
in cells, used as an alternative energy source
are all uncommon amino acids found in proteins?
no. creatine in skeletal muscle
ADP + phsophocreatine ->ATP + creatine
how are amino acids linked to form proteins?
peptide bonds
how are peptide bonds fomred?
condensation of the alpha carboxyl of one amino acid with the alpha-amino of another
