Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

USMLE Step 1 > Biochem, Molecular > Flashcards

Biochem, Molecular Flashcards

1
Q

What vitamin should be supplemented with neonatal phototherapy?

A

riboflavin (B2) bc the light degrades it

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Name a genetic disorder that is assoc w abnormal splicing variants.

A

Beta-thalassemia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the effects of medium/long-chain acyl-CoA dehydrogenase deficiency? Tx?

A 
Inability to beta-oxidize fatty acids = accumulation of carnitines + less ATP
-hypoketotic hypoglycemia
-hypotonia (frog leg)
-seizures
-hyperammonia
Tx: avoid fasting
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Which base pairs indicate splice acceptor site? Splice donor site?

A

acceptor: 3’ invariant AG
donor: 5’ GT/GU

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the symptoms and treatment for Galastosemia?

A

Absent galatose-1-P UT = cataracts, fail thrive, jaundice

Tx: remove galactose + lactose/glucose from diet

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is primase?

A

Complex that synthesizes a short strand of RNA that’s needed before DNA can be synthesized

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is Beriberi in adults?

A

Profound thiamine def

  • dry = peripheral neuropathy
  • wet = cardiac involvement
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the symptoms of UMP synthase def?

A

blockage of pyrimidine synthesis –> megaloblastic anemia w orotic crystals in urine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Which 2 enzymes does citrate allosterically affect?

A

negative regulator: phosphofructokinase I (PFK I) (glycolysis)
positive regulator: acetyl CoA carboxylase (fatty acid syn)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the risk factors for severe hyperbilirubemia in neonates?

A
  • male
  • premature
  • jaundice within 24hrs
  • maternal use of TMP-SMX (binds albumin which cant bind bili = kernicterus)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How does cortisol stimulate glucose production?

A

Cortisol induces gluconeogenic enzymes by increasing gene expression (not via cascades)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How does delta F508 mutation affect the CFTR gene?

A

Prevents proper folding = unstable and ubiquinated and digested

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Lipoprotein lipase catalyzes what process?

A 
Breakdown of triglycerides in chylomicrons into free fatty acids and glycerol
def = accumulation of chylos --> milky plasma
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is Lesch-Nyhan Syndrome and its symps?

A 
HGPRT def = excess purine synthesis (hyperuricemia)
-spastic cerebral palsy
-self-mutilation*(hand/lips)
-gout/arthritis
TX: allopurinol
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

lead poisoning inhibits which 2 enzymes?

A
  1. aminolevulinate dehydratase (ALA)
  2. ferrochelatase
    = microcytic, hypochromic anemia
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is familial hypocalciuric hypercalcemia (FHH) and its symps?

A

mutation in Ca-sensing receptor gene (CaSR) = no feedback inhibition of PTH –> hyperCa, hypoCa in urine, Hyper/norm PTH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How does phenylalanine affect a fetus (mom w PKU)?

A

Phenylalanine crosses the placenta; if elevated can act as a teratogen to fetus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is Acute Intermittent Porphyria and its symps?

A 
Porphobilinogen deaminase def = inc urinary delta-ALA and PBG; 5 Ps:
Painful abdomen
ƒ Port wine–colored urine
ƒ Polyneuropathy (tachy, HTN)
ƒ Psychological disturbances
ƒ Precipitated by drugs
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What enzyme is mutated in Ehlers-Danlos Syndrome and what does it do?

A

Lysyl hydroxylase; hydroxylation of lysine residues for cross-linking collagen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is Pompe disease (II)?

A

alpha-1,4-glucosidase def = skeletal and cardiac muscle symps (cardiomegaly, hepatomegaly, heart fail); NO hypoglycemia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is the molecular mechanism for a trinucleotide repeat expansion mutation?

A

DNA replication error during S-phase; caused by slippage of polymerase during replication of repeat regions

22
Q

What is the biochemical mechanism behind hemorrhagic disease of the newborn?

A

Vit K def –> defective gamma-carboxylation of glutamate residues
-antibiotics can interfere w Vit K production in breast milk

23
Q

What is I-cell Disease?

A

defect in N-acetylglucosaminyl-1-phosphoTRANSFERASE
= golgi fails to phosphorylate mannose –> proteins secreted extracellularly not delivered to lysosomes
-coarse facial features
-immobile joints
-high plasma lyso enzymes
-cell inclusions

24
Q

What is Glucose-6-phosphate Dehydrogenase def?

A

= less NADPH –> RBCs vulnerable to oxidative damage

  • hemolytic anemia w Heinz bodies + Bite cells
  • anemia precipitated by antimalarials, fava beans, sulfas
25
What are the hallmarks of Vit C def?
Scurvy: swollen gums, bruising/petechiae, perifollicular hemorrhages, corkscrew hair
26
How are cocaine and PFK-1 related?
Cocaine blocks norepi --> tachy + vasoconstrict = cardiac ischemia and switch to anaerobic metabolism --> Inc PFK-1 to switch from aerobic to anaerobic
27
What is Maple Syrup Urine Disease?
def of branched-chain ketoacid dehydrogenase = no breakdown Iso,Leu,Val - lethargy, poor feeding, vomiting - CNS: convulsions, coma - Mennonites in PA
28
When an obese person diets, where does the majority of glucose come from?
glycerol from fat breakdown
29
What is the composition of gallstones from in ppl w hemolytic anemia (sickle cell)?
calcium bilirubinate
30
A diet containing milled rice is associated with what vitamin def?
Thiamine --> Beriberi (dry:polyneuritis, muscle waste) (wet: cardiomyopathy, edema)
31
Describe a fructose-1-phosphate aldolase (aldolase B) def.
= accumulation of fructose-1-phosphate which inhibits glycogenolysis and gluconeogenesis --> severe hypoglycemia when eating fruit
32
Describe a pyruvate carboxylase def.
PyrCarb converts Pyruvate --> oxaloacetate; enzyme def = build up of precursors alanine, pyruvate, lactate - seizures - hypotonia - developmental delay
33
Where are chylomicrons produced?
enterocytes (intestinal epi cells) using dietary lipids
34
Where are chylomicrons metabolized?
vascular endothelium of adipose tissue via lipoprotein lipase
35
Describe Pyruvate kinase def.
= dec ATP = rigid RBCs (hemolytic anemia), inc 2,3-BPG - hemolytic anemia of newborn - mild for adults - autosomal recessive (G6PD def is x-linked)
36
What are hallmarks associated with Hereditary Nonpolyposis colon cancer?
- microsatellite instability (dinucleotide) | - loss of function in mismatch repair genes MLH1/MSH2
37
What is Niemann-Pick Disease?
Sphingomyelinase def = neurodegen, hepatosplenomegaly, foam cells (fat macros) Note: No hepato in Tay-Sachs
38
What is ataxia telangiectasia?
``` defect in ATM gene = no DNA ds break repair Triad: -ataxia (wheelchair) -angiomas (telangiestasias) -IgA def ```
39
NO activates which enzyme to cause vasodilation?
Guanylate cyclase
40
Von Gerke (I) is def in what enzyme?
glucose-6-phosphate
41
Pompe (II) is def in what enzyme?
alpha-1,4-glucosidase aka acid maltase
42
Cori (III) is def in what enzyme?
debranching enzyme aka alpha-1,6-glocosidase
43
McArdle (V) is def in what enzyme?
glycogen phosphorylase aka myophosphorylase
44
What are the essential amino acids?
``` PVT TIM HALL Phen Val Tryp Thre Iso Met His Arg Lys Leu ```
45
What is homocystinuria?
Cystathionine synthase def = marfanoid, kyphosis, lens dislocation, intellect disability
46
What does AATAAA code for?
Cleavage and polyadenylation
47
Cancer/tumor antigen to produce the highest antibody titer?
HPV 16 E6 (p53) bc its a mutant tumor suppressor, so body attacks w abs
48
What do tyrosine kinases do?
act as downstream effectors of various growth factors, they function through phosphorylating tyrosine residues on different proteins
49
What needs to be inhibited in methanol (paint thinner) poisoning?
alcohol dehydrogenase bc it forms formaldehyde
50
What does ribosome peptidyl transferase do?
Establish covalent bonds between amino acids
51
Impaired voltage-gated Na channels would cause what?
slowed conduction (of myelin sheath)

USMLE Step 1 (13 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions