PHM 320 MIDTERM EXAM
Deaminases cause:
-C --> U
-5-methylC --> T (DNA methylation)
Proteinogenic amino acids
- amino acids that are incorporated biosynthetically into proteins during translation (20
amino acids)
Base I can pair with:
- C, U, A
How does wobbling help bacteria?
- can help to bypass mutations
Where is most of the energy in the nucleus spent?
- 80% spent repairing DNA
2 step reaction catalyzes by aminoacyl-tRNA synthetase
- 1. cleavage of ATP and addition of aminoacyl-AMP
2. addition of tRNA and loss of AMP and enzyme
*checks work along the way
How many aminoacyl-tRNA synthetases are there?
- 1 per amino acid
Prokaryotic protein synthesis initiation:
, -step 1
1. fMet attaches to initiator tRNA
2. ribosome recognizes start codon (AUG) using ribosome binding site (Shine-Dalgarno
sequence) which is complementary to 3' end of 16S rRNA on 30S subunit
3. IF3 recognizes start codon and prevents premature binding of 50S to 30S
3. IF2-GTP stabilizes acceptor stem of fMet-tRNA and escorts initiator tRNA to P site
4. as soon as initiator tRNA binds to P site, GTP on IF2 is hydrolyzed and all initiation factors
are released so 50S subunit can bind to 30S subunit
Prokaryotic protein synthesis elongation
- 1. fMet tRNA is at P site, next amino acid arrives at A site
2. fMet binds to second amino acid, catalyzed by peptidyl transferase reaction (using
ribozyme 23S rRNA on 50S subunit)
3. ratcheting/translocation: (EF-G)(GTP) complex bind to ribosome on 50S, GTP is hydrolyzed -
-> ratchets ribosome forward to next codon --> A site is open
4. tRNA in E site is ejected
Prokaryotic protein synthesis termination
- 1. ribosome encounters stop codon -- no tRNA exists for stop codon so RFs bind
2. RF1 recognizes UAA and UAG; RF2 recognizes UAA or UGA
Transcription and translation can occur simultaneously in ______ cells
(eukaryotic/prokaryotic/both/neither)
- prokaryotic
Phospholipid composition (in cell membrane)
-2 fatty acids connected to glycerol via ester linkages
-connected to polar head via phosphate group
Eubacteria cell composition
-cell membrane with ester linkages (like eukaryotes)
Deaminases cause:
-C --> U
-5-methylC --> T (DNA methylation)
Proteinogenic amino acids
- amino acids that are incorporated biosynthetically into proteins during translation (20
amino acids)
Base I can pair with:
- C, U, A
How does wobbling help bacteria?
- can help to bypass mutations
Where is most of the energy in the nucleus spent?
- 80% spent repairing DNA
2 step reaction catalyzes by aminoacyl-tRNA synthetase
- 1. cleavage of ATP and addition of aminoacyl-AMP
2. addition of tRNA and loss of AMP and enzyme
*checks work along the way
How many aminoacyl-tRNA synthetases are there?
- 1 per amino acid
Prokaryotic protein synthesis initiation:
, -step 1
1. fMet attaches to initiator tRNA
2. ribosome recognizes start codon (AUG) using ribosome binding site (Shine-Dalgarno
sequence) which is complementary to 3' end of 16S rRNA on 30S subunit
3. IF3 recognizes start codon and prevents premature binding of 50S to 30S
3. IF2-GTP stabilizes acceptor stem of fMet-tRNA and escorts initiator tRNA to P site
4. as soon as initiator tRNA binds to P site, GTP on IF2 is hydrolyzed and all initiation factors
are released so 50S subunit can bind to 30S subunit
Prokaryotic protein synthesis elongation
- 1. fMet tRNA is at P site, next amino acid arrives at A site
2. fMet binds to second amino acid, catalyzed by peptidyl transferase reaction (using
ribozyme 23S rRNA on 50S subunit)
3. ratcheting/translocation: (EF-G)(GTP) complex bind to ribosome on 50S, GTP is hydrolyzed -
-> ratchets ribosome forward to next codon --> A site is open
4. tRNA in E site is ejected
Prokaryotic protein synthesis termination
- 1. ribosome encounters stop codon -- no tRNA exists for stop codon so RFs bind
2. RF1 recognizes UAA and UAG; RF2 recognizes UAA or UGA
Transcription and translation can occur simultaneously in ______ cells
(eukaryotic/prokaryotic/both/neither)
- prokaryotic
Phospholipid composition (in cell membrane)
-2 fatty acids connected to glycerol via ester linkages
-connected to polar head via phosphate group
Eubacteria cell composition
-cell membrane with ester linkages (like eukaryotes)
