Translation and Post-translation 2C part 1 Flashcards
translation is the
assemble of amino acids into polypeptides
tell me the structure of an amino acid
amine group+central carbon+hydrigen+carboxyl group and a different R group
R group
This is what determines the unique character of an amino acid. What makes amino acid different
Tell me how two amino acids are joined (3)
+ what is the bond called
they are joined by a covalent peptide bond between the amino and carboxyl by a dehydration reaction.
The COH (part of COOH) reacts with the amine part hydrogen to form water molecule and the conjoined two amino acid.
carboxyl carbon join with amine nitrogen
Polypeptides
linear chains of amino acids linked by peptide bonds
Non polar amino acid
R group usually contain CH2 or CH3
uncharged polar amino acids
R groups usually contain oxygen of OH
charged amino acids
R groups contain acids or bases that can ionize
Aromatic amino acid
R group contain a carbon ring with alternating single and double bonds
Methionine
First amino acid in polypeptide
Proline
causes kink/bend in polypeptide chains
Cysteine
disulphide bridge where the R group interact
Primary amino acid sequence (3)
determines protein folding and 3D structure which is critical for proper function
just the linear sequence held together by peptide bond
no attention to 3D shape
Secondary protein structure (3)
depends on hydrogen bonding in the peptide backbone (alpha helices and beta-sheets).
secondary structure does not involve R group atoms
hydrogen bonds, which form between the carbonyl and amino group of the peptide bond
Tertiary protein structure (2)
the 3D structure of a single polypeptide and is composed of interactions between amino acid side chains
R groups interactions: ionic bonding, H bond, Vanderwall, Disulphide interaction and hydrophilic/hydrophobic
Quaternary protein structure (2)
Interactions between more than one polypeptide to form a multi-subunit proteins eg: hemoglobin
hydrogen bonds, covalent bonds, or ionic bonds.
how can protein structures be denatured (3)
heat
chemicals
mutations that change amino acid sequence
Chaperones (3)
protect slow folding or denatured proteins by preventing their aggregation
assist large proteins in proper protein folding during or after synthesis, and after partial denaturation
assist in protein folding by binding to and stabilizing folding intermediates until the polypeptide chain is fully translated.
aggregation (2)
associated with….
intrinsically-disordered or mis-folded proteins aggregate (i.e., accumulate and clump together)
associated with Alzheimer’s, Parkinson and Creutzfeldt-Jakob
tRNAs
adaptors between codons (mRNA) and amino acids
2-D 3 cloverleaf and 3-D L shaped folded RNA molecule from complimentary pairing.
Acceptor stem tRNA (2)
Where amino acid is attaches
contains the sequence 5’-CCA-3’ at the end of the 3’ end of tRNA
Anticodon (3)
the bottom loop of the cloverleaf contains three nucleotide sequence that recognize the codon by base pairing with mRNA
Each tRNA has its corresponding amino acid attached to its end.
anticodon binding to codon is antiparallel
aminoacyl-tRNA synthase (2)
adds amino acid to the acceptor stem of the correct tRNA
20 different aminoacyl-tRNA synthase for 20 different amino acids
charging reaction (3)
aminoacyl-tRNA synthase binds with ATP and amino acid causing two pyrophosphates to be released and ATP turns to AMP. Amino acid+AMP complex is formed
Correct tRNA binds with the enzyme.( Amine group free) The enzyme transfer amino group to tRNA. Amp is then released.
Amino acid-tRNA is released
What does the Amp do in tRNA charging?
The animoacyl tRNA synthetase used the energy supplied by ATP to charge the tRNA with the correct amino acid so that it can be used again in the process of translation.
sense codon
codes for amino acid
codons are written in the table
5’-3’ as they appear in the mRNA
CUU
5’-3’
Stop codons +which codes
(5)
UAA
UAG
UGA
do not code for amino acids. tRNA does not bind to these codons
STOP codons cause the release of the new polypeptide chain from the ribosome
degeneracy in genetic code
more than one codon can specify an amino acid
how many codons
Sense+total
61 sense codons
64 total codons
Tell me about methionine group in translation
first methionine that ribosome encounter as it travels 5’-3’ is start codon
ribosome gets recruited to
5’ cap of mRNA and start to read
codons are read ……
not the 5’-3’ part
non overlapping and no gaps. read 1 nucleotide just once and in 3s
+4 frame
same +1 frame
wobble (3)
degeneracy
used words like codon+anticodon
general
there are less than 61 tRNA because some tRNA can read/bind more than 1 codon
this is because the base at the 5’ end of the anticodon can form H bonds with more than one type of base located at the 3’ end of a codon.
Binding of a codon in an mRNA the cognate tRNA is much “looser” in the third position of the codon. This permits several types of non-Watson–Crick base pairing to occur at the third codon position
flexibility occurs only at the _____ end of the anticodon
5’
pairing of the other 2 nucleotides in the anticodon
is percise/no wobble
