USMLE step 1 biochemistry: Difference between revisions
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{{CMG}} {{MIR}} | {{CMG}} {{MIR}} | ||
Ribosomes are made of proteins and rRNA | |||
* Eukaryotes → 60 and 40s = 80s | |||
* Prokaryotes → 50 s and 30 s = 70 s | |||
** Have 23s in 50s | |||
Translation | |||
* Initiation | |||
** IF1, IF2, If3 | |||
*** Assist in assembly of smaller ribosomal subunit to first trna molecule | |||
*** Methionine is always the start | |||
*** f-Methionine in prokaryotes | |||
*** IF-2 first binds to 30s and then to methionine tRNA. Then when 50s comes along, it hydrolyzes GTP on IF2 and allows 50s to attach to 30s | |||
** A site → Incoming aminoacyl TRNA binds | |||
** P site → Polypeptide binds (Growing chain) | |||
*** First tRNA binds here | |||
** E site → Free tRNA (exit) | |||
* Elongation | |||
** Incoming charged aminoacyl TRNA binds to A site | |||
** Elongation factor help incoming trna to bind to A site (Uses GTP) | |||
** 50s has peptidyl transferase transfers AA from p site to A site | |||
*** In prokaryotes, activity is in 23s subunit of 50s rRNA | |||
** '''Translocation''' | |||
*** Ribosome complex moves 3 nucleotides | |||
*** tRNA + Peptide is moved from A site to P site | |||
*** Newly uncharged tRNA from P side to E side | |||
*** EF-G → Eukaryotes | |||
*** EF-2 in eukaryotes | |||
**** Diptheria and exotoxin (Pseudomonas) inhibit this | |||
* Termination | |||
** Stop codons | |||
*** UGA, UAA and UAG | |||
*** Signal to STOP | |||
*** No new TRNA coming | |||
*** Release factor binds to MRNA and hydrolyzes GTP and new polypeptide is released. | |||
* Antibiotics | |||
** Aminoglycosides → Inhibit 30s subunit before initiation (No pairing with TRNA) | |||
** Linezolid → Inhibits initiation by binding to 50s subunit | |||
** Tetracycline | |||
*** Bind to 30s subunit | |||
*** Prevent aminoacyl TRNA from binding to A site | |||
** Chloramphenicol | |||
*** Inhibits peptidyl transferase | |||
*** Binds to 50s | |||
** Macrolides | |||
*** Inhibits translocation by binding to 50s subunit | |||
** Clindamycin | |||
*** Same as macrolides | |||
** Lincamycin | |||
*** Bind to 50s and inhibit translocation | |||
** Streptrogranin | |||
*** Bind to 50s and inhibit translocation | |||
** Buy AT 30 ,CCELL at 50 | |||
* Post translational modification | |||
** Trim terminals | |||
** Covalent modification | |||
*** Glycosylation, hydroxylation, phosphorylation | |||
*** Collagen → Hydroxylation of proline and lysine | |||
** Disulfide bonds | |||
** Protein folding | |||
*** Primary structure → Chain | |||
*** Secondary structure → Beta and alpha pleated | |||
*** Tertiary structure | |||
Latest revision as of 22:32, 26 September 2018
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Mahshid Mir, M.D. [2]
Ribosomes are made of proteins and rRNA
- Eukaryotes → 60 and 40s = 80s
- Prokaryotes → 50 s and 30 s = 70 s
- Have 23s in 50s
Translation
- Initiation
- IF1, IF2, If3
- Assist in assembly of smaller ribosomal subunit to first trna molecule
- Methionine is always the start
- f-Methionine in prokaryotes
- IF-2 first binds to 30s and then to methionine tRNA. Then when 50s comes along, it hydrolyzes GTP on IF2 and allows 50s to attach to 30s
- A site → Incoming aminoacyl TRNA binds
- P site → Polypeptide binds (Growing chain)
- First tRNA binds here
- E site → Free tRNA (exit)
- IF1, IF2, If3
- Elongation
- Incoming charged aminoacyl TRNA binds to A site
- Elongation factor help incoming trna to bind to A site (Uses GTP)
- 50s has peptidyl transferase transfers AA from p site to A site
- In prokaryotes, activity is in 23s subunit of 50s rRNA
- Translocation
- Ribosome complex moves 3 nucleotides
- tRNA + Peptide is moved from A site to P site
- Newly uncharged tRNA from P side to E side
- EF-G → Eukaryotes
- EF-2 in eukaryotes
- Diptheria and exotoxin (Pseudomonas) inhibit this
- Termination
- Stop codons
- UGA, UAA and UAG
- Signal to STOP
- No new TRNA coming
- Release factor binds to MRNA and hydrolyzes GTP and new polypeptide is released.
- Stop codons
- Antibiotics
- Aminoglycosides → Inhibit 30s subunit before initiation (No pairing with TRNA)
- Linezolid → Inhibits initiation by binding to 50s subunit
- Tetracycline
- Bind to 30s subunit
- Prevent aminoacyl TRNA from binding to A site
- Chloramphenicol
- Inhibits peptidyl transferase
- Binds to 50s
- Macrolides
- Inhibits translocation by binding to 50s subunit
- Clindamycin
- Same as macrolides
- Lincamycin
- Bind to 50s and inhibit translocation
- Streptrogranin
- Bind to 50s and inhibit translocation
- Buy AT 30 ,CCELL at 50
- Post translational modification
- Trim terminals
- Covalent modification
- Glycosylation, hydroxylation, phosphorylation
- Collagen → Hydroxylation of proline and lysine
- Disulfide bonds
- Protein folding
- Primary structure → Chain
- Secondary structure → Beta and alpha pleated
- Tertiary structure