100% satisfaction guarantee Immediately available after payment Both online and in PDF No strings attached
logo-home
Biochemistry USMLE step 1 Exam Questions with Correct Verified Answers Latest Update (2024/2025) Guaranteed Pass $12.99   Add to cart

Exam (elaborations)

Biochemistry USMLE step 1 Exam Questions with Correct Verified Answers Latest Update (2024/2025) Guaranteed Pass

 6 views  0 purchase

Biochemistry USMLE step 1 Exam Questions with Correct Verified Answers Latest Update (2024/2025) Guaranteed Pass Biochemistry USMLE step 1 Exam Questions with Correct Verified Answers Latest Update (2024/2025) Guaranteed Pass Biochemistry USMLE step 1 Exam Questions with Correct Verified Answ...

[Show more]

Preview 4 out of 108  pages

  • August 20, 2024
  • 108
  • 2024/2025
  • Exam (elaborations)
  • Questions & answers
All documents for this subject (31)
avatar-seller
DoctorKen
1
USMLE




Biochemistry USMLE step 1 Exam
Questions with Correct Verified
Answers Latest Update (2024/2025)
Guaranteed Pass
Inhibit dihydrofolate reductase (DHFR) - ANS ✓methotrexate (MTX) in
humans
Trimethoprim (TMP) in bacteria
Pyrimethamine in protozoa


Prevents pyrimidine synthesis (dump --> dtmp)


Folate is supplemental for which drugs and why? - ANS ✓5-FU >
increase potency
MTX > reduce side effects


Major cause of AR SCID and why - ANS ✓adenosine deaminase (ADA)
deficiency


Prevents purine salvage, affects cells that need to divide a lot
(immune cells > reduces lymphocyte count)


Pathophys of adenosine deaminase (ADA) deficiency - ANS ✓buildup of
adenosine (bc low ADA prevents degradation) > feedback inhibition of


Biochemistry USMLE step 1

, 2
USMLE

ribonucleotide reductase --I DNA synthesis --> dec lymphocyte count and
causes immunodeficiency (SCID)


Purine salvage enzyme & function - ANS ✓HGPRT


Recycles:
Hypoxanthine > IMP
Guanine > GMP


Key enzymes of purine degradation - ANS ✓ADA (adenosine > inosine)
XO (hypoxanthine > xanthine > uric acid)


Purine degradation overview - ANS ✓1. Removal of phosphate from
nucleotide
2. Removal of sugar from nucleoside
3. Convert free bases (guanine & hypoxanthine) to xanthine by
xanthine oxidase (XO)
4. Xanthine > uric acid by xanthine oxidase (XO)
5. Uric acid to urine


Defective purine salvage due to absent HGPRT (dz name) - ANS
✓Lesch-Nyhan syndrome


Symptoms of Lesch-Nyhan syndrome - ANS ✓HGPRT deficiency:
Hyperuricemia
Gout
Pissed off (aggression, self-mutilation)


Biochemistry USMLE step 1

, 3
USMLE

Retardation
Dystonia


Young male
Gout
Aggression, self-mutilation
Intellectual disability
Dystonia - ANS ✓Lesch-Nyhan syndrome


Defective purine salvage due to absent HGPRT --> excessive uric acid
production and de novo purine synthesis


Function of HGPRT - ANS ✓purine salvage (adds sugar/P to free base)
Converts hypoxanthine + PRPP --> IMP
Converts guanine + PRPP --> GMP


Inheritance of Lesch-Nyhan syndrome - ANS ✓X-linked recessive


Treatment of Lesch-Nyhan syndrome - ANS ✓XO-inhibitors: allopurinol
or febuxostat (2nd line)


Reduce uric acid causing hyperuricemia and sxs


XO-inhibitors reduces the efficacy of which drugs - ANS ✓drugs that
look like purines (6-MP, leukemia tx)


AA encoded by only 1 codon - ANS ✓AUG --> methionine


Biochemistry USMLE step 1

, 4
USMLE

UGG --> tryptophan


Create single or double stranded breaks in DNA helix to add or
remove supercoils - ANS ✓DNA topoisomerases


Unwinds DNA template at replication fork - ANS ✓helicase


"helicase has the most fun bc it spends all day unzipping genes!"


Bonds helicase breaks - ANS ✓H-bonds only


Inhibit prokaryotic enzymes topoisomerase II (DNA gyrase) and
topoisomerase IV - ANS ✓fluoroquinolones


Direction of DNA and RNA synthesis & protein synthesis &
implications - ANS ✓5' --> 3'
N' --> C'


Drugs (AZT) can target triphosphate bond @ 3' hydoxyl


Found in prokaryotes only, has 5' --> 3' synthesis and 3' --> 5'
exonuclease proofreading - ANS ✓DNA pol III


Makes RNA primer on which DNA polymerase III can initiate
replication - ANS ✓Primase




Biochemistry USMLE step 1

The benefits of buying summaries with Stuvia:

Guaranteed quality through customer reviews

Guaranteed quality through customer reviews

Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.

Quick and easy check-out

Quick and easy check-out

You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.

Focus on what matters

Focus on what matters

Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!

Frequently asked questions

What do I get when I buy this document?

You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.

Satisfaction guarantee: how does it work?

Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.

Who am I buying these notes from?

Stuvia is a marketplace, so you are not buying this document from us, but from seller DoctorKen. Stuvia facilitates payment to the seller.

Will I be stuck with a subscription?

No, you only buy these notes for $12.99. You're not tied to anything after your purchase.

Can Stuvia be trusted?

4.6 stars on Google & Trustpilot (+1000 reviews)

79271 documents were sold in the last 30 days

Founded in 2010, the go-to place to buy study notes for 14 years now

Start selling
$12.99
  • (0)
  Add to cart