USMLE step 1 biochemistry: Difference between revisions

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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)
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

@@ Line 1: / Line 1: @@
 __NOTOC__
 {{CMG}} {{MIR}}
 Ribosomes are made of proteins and rRNA
@@ Line 62: / Line 63: @@
 *** Secondary structure → Beta and alpha pleated
 *** Tertiary structure
-Purine synthesis:
-You need glycine, glutamine and aspartate + tetrahydrofolate (Folic acid) + CO2
-Rate limiting step : Glutamine PRPP amidotransferase
-Carbon sources:
-CO2, glycine, tetrahydrofolate
-Nitrogen sources
-Aspartate + Glutamine
-Pyrimidines: Aspartate + carbamoyl phosphate (1 carbon and 1 nitrogen [glutamine]) + ATP
-Carbamoyl phosphate → Has 1 carbon and 1 nitrogen
-You need aspartate + CO2 + glutamine + ATP (Last 3 come from carbamoyl phosphate)
-Carbamoyl phosphate synthetase 2 (RATE LIMITING STEP)
-Start with orotic acid then add a base
-Carbon sources:
-Aspartate
-CO2
-Glutamine → Gives nitrogen
-CPS 1 + CPS 2
-CPS 1
-Mitochondria
-Urea cycle
-Use nitrogen from ammonia
-CPS 2
-Cytosol
-Pyrimidine synthesis
-Use nitrogen from glutamine
-Orotic aciduria
-Deficiency of UMP synthase
-AR
-Elevated oritic acid
-Megaloblastic anemia
-Not corrected with B12 or folic acid
-No hyperammonemia
-Treat with uridine
-Ornithine Transcarbomylase Deficiency
-Causes hyperammonemia
-Elevated orotic acid
-Problem with urea cycle
-Dantrolene → Prevents release of calcium from SR of skeletal muscle
-Inhibit reuptake of norepinephrine:
-Cocaine
-TCA
-Ribosomes are synthesized in the nucleus and transported into the cytoplasm.
-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)
-s 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

USMLE step 1 biochemistry: Difference between revisions

Latest revision as of 22:32, 26 September 2018

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