Theme 2c Flashcards
What is the structure of an amino acid
Contain an amino and carbonyl bonded to a central carbon with a hydrogen and a R group
Joined together by a peptide bond
What are peptides
Linear chains of amino acids linked by peptide bomds
Draw the structure of an amino acid
How can non polar amino acids be identified
R groups contain -CH2 or -CH3
How can an uncharged amino acid be identified
R groups contain oxygen or -OH
How can charged amino acids be identified
R groups contain acids or bases that can ionize
How can aromatic amino acids be identified
R groups contain a carbon ring with alternating single and double bonds
What are the 3 special functional amino acids
1) methionine: first amino acid in polypeptide
2) proline: causes kink in polypeptide chains
3) cysteine: disulfide bridge contributes to structure of polypeptides
What is the general function of tRNAs
Adaptors between codons (mRNA) and amino acids
What type of RNA are codons and anticodons and how to they base pair (parallel or antiparallel)
Codon = mRNA
Anticodon = tRNA
Antiparallel base pairing
What is aminoacyl-tRNA
Adding the amino acid to the acceptor stem tRNA
What is the charging reaction
amino acid + tRNA + ATP —> aminoacyl-tRNA + AMP + PPi
What is the “wobble” in the tRNA anticodon
The base at the 5’ end of the anticodon can form H-bonds more then the base located at the 3’ end of a codon
Pairing of the other two nucleotides in the anticodon with the codon is precise (no wobble)
What are the two subunits that make up ribosomes
Large (50s): contains enzymes activity called peptidyltransferase
Small (30s): reads codons of mRNA
*exist separately in the cytoplasm but join together on the mRNA molecule
What are the 3 tRNA binding sites
1) aminoacyl (A): binds to the tRNA carrying the next amino acid to be added
2) peptidyl (P): binds to the tRNA attached to the growing peptide chain
3) exit (E): binds the tRNA that carried the previous amino acid added
In eukaryotes what does the translation initiation complex contain
The ribosome, mRNA and the initiator tRNA
Where is the initiatior tRNA^met brought on the small ribosome subunit
The p-site (reaction requires GTP)
Then goes to the capped 5’ end of mRNA and scans until it reached the start codon
How does the initiator tRNA^met help to initiate translation
Complementary base pairing between it and start codon on mRNA
Large ribosomal subunit bind small subunit to form initiation complex which can now accept the first tRNA in the A site
GTP is hydrolyzed to GDP and translation begins
What are the 4 steps of translation elongation
1) aminoacytl tRNA is loaded to the A-site and complementary to the tRNA anticodon
2) peptidyl transferase (large subunit) forms a peptide bond between carboxyl group and amino group in the A site
3) tRNA with the polypeptide shifts from A to P site and uncharged tRNA shifts from P to E site (ejected)
4) next codon is now in the A site and steps repeat
What proteins recognize the stop codons
Release factors
Do ribosome subunits, mRNA and tRNA get recycled
Yes
What is phosphoraylation
Addition of phosphate to proteins by kinase
What is ubiquitination
Addition of ubiquities molecules to proteins for their destruction by proteasomes
Controls protein expression
What is proteolysis
Specific cleavage at the protein
What is epigenetics
Posttranslational modification of histones that affect transcription
No change in DNA sequence
What does histone acetyltransferase add to histone tails and why
Add acetyl groups (CH3CO-) by loosening DNA binding
Because if histone become more negative then DNA will pull away
What does the methylation of histone tails do
Can activate and repress transcription of genes
What does chromatin remodelling complex do
Displeases nucleosides from promoter regions and activates transcription
What is translational regulation
Control of protein synthesis
What is Posttranslational regulation
Control of protein abundance and activity
