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USMLE Step 1 Quick Notes > Biochemistry > Flashcards

Biochemistry Flashcards

1
Q

What is the only RNA molecule to have thymidine?

A

tRNA

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2
Q

What are people with fabry disease at risk for?

A

CVD and renal failure

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3
Q

What is the problem if you have methylmalonyl acidemia?

A

Defect in the isomerization reaction that forms succinyl coA from methylmalonyl coA

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4
Q

What did propionyl coA carboxylase do?

A

Convert propionyl coA to mehylmalonyl coA and requires B7 (biotin)

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5
Q

What makes propionyl coA?

A

Methionine, Threonine, Valine, Isoleucine

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6
Q

Where does repressor bind?

A

Operator

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7
Q

What is a positive regulator of the lac operon?

A

cAMP - CAP

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8
Q

What prevents lactose fermenting bacteria to stop fermenting when glucose added?

A

Glucose depletes cAMP so cAMP - CAP can’t positively regulate lac operon.

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9
Q

What does it mean if collagen containing disulfide rich globular domains present?

A

Procollagen deficiency

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10
Q

What does citrate synthase use?

A

B5

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11
Q

Several tissues use TG breakdown products as intermediates in energy generation and glucose synthesis. Which is a liver specific enzyme that facilitates this?

A

Glycerol kinase: TG broken down into glycerol and FA by lipase. The glycerol is phosphorylated in the liver to glycerol 3 phosphate then converted to DHAP. Can be used for glycolysis or gluconeogenesis.

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12
Q

What is Rotenon?

A

Inhibits complex 1 of ETC

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13
Q

What is antimycin?

A

Inhibits complex III of ETEC

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14
Q

What do CN, CO inhibit?

A

Complex IV of ETEC

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15
Q

What is Oligomycin?

A

Inhibits complex V aka ATP synthase of ETC

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16
Q

Do even chain or odd chain yield glucose?

A

Odd chain

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17
Q

What is Osler-Weber-Rendu?

A

Hereditary hemorrhagic telangiectasia: epistaxis, telangiectasia, skin discoloration, AVM

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18
Q

What do you see on histology for Duchenne MD?

A

Fibrofatty change in muscle

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19
Q

What is type I familial dyslipidemia?

A

Problem with LPL. Acute pancreatitis, eruptive xanthomas, hepatosplenomegaly

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20
Q

What is type II familial dyslipidemia?

A

LDL receptor problem. Tendon xanthomas, xanthelasmas, increased atherosclerosis

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21
Q

What is type IV familial dyslipidemia?

A

VLDL overproduction. Get acute pancreatitis

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22
Q

What does succinate DH use?

A

Riboflain to make FADH2

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23
Q

Where does proteolytic processing of collagen occur?

A

Cleavage of N & C terminal occurs outside of cell

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24
Q

What is the problem with collagen processing in scurvy, osteogenesis, ehler’s danlos?

A

Scurvy: Hydroxylation
Osteogenesis Imperfecta: triple helix formation
Ehler’s Danlos: proteolytic processing or cross-linking

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25
What is the problem in XP?
Endonuclease messed up
26
What is a long term consequence of alkaptonuria (aka ochronosis)?
Debilitating arthritis (homogentisate is harmful to cartilage) Other sx: dark CT, brown sclera, urine turns dark on prolonged exposure to air
27
What do the TATA and CAAT boxes do?
Promoters of transcription in eukaryotic cells. CAAT is more upstream than TATA. This is where RNA Pol II binds
28
What is a protein with seven alpha helical transmembrane domain?
GPCR
29
What causes different length fragments to be produced on RFLP?
SNPs They change where restriction enzyme would cleave and so the DNA is no longer cleaved there and would be bigger on gel electrophoresis
30
What is MCAD?
AR characterized by inability to degrade medium length fatty acids by beta oxidation. Present early in childhood with hypoketotic hypoglycemia and hepatic dysfunction
31
What does a short alpha helical fragment with leucine residues every 7th position do?
Part of leucine zipper dimerization domain in transcription factor (basic zipper proteins) Other DNA binding protein: helix loop helix and zinc fingers
32
If radiolabeled CO2 added to proliferating cells and gets added to DNA, where was the first step?
Cytoplasm De novo purine and pyrimidine synthesis occurs in cytoplasm
33
What catalyzes the first step in pyrmidine synthesis?
Carbamoyl phosphate synthase II | carbamoyl phosphate synthase I is in the urea cycle
34
How do you tell Cori and Von Gierke's apart?
Fructose administration will not improve von Gierke's but will improve Cori
35
Where is the enzyme deficiency in pompe's?
LYSOSOMES! It is the only one of the glycogen storage disorders to be a lysosomal defect
36
What does increased malonyl coA inhibit?
Fatty acid oxidation
37
What can classic galactosemia lead to in neonates?
E. coli sepsis
38
What is glucose oxidase test for?
To test for amount of glucose in urine
39
What is propionyl coA carboxylase deficiency?
Pw/ vomiting, dehydration, acidemia, anion gap acidosis, ketosis High propionyl coA levels
40
What is propionyl coA made from?
Threonine, methionine, isoleucine, valine
41
What presents with kinky matted hair, growth retardation, and hypotonia?
Menke's (Impaired CU absoption due to lysyl oxidase activity)
42
What do transketolase/transaldolase do?
Converts ribose 5 phosphate to fructose 6-phosphate and glyceraldehyde 3 phosphate
43
What controls cytoplasmic quality of mRNA?
P bodies
44
What cofactors required for pyruvate DH?
Lipoic acid and B1 - B5
45
How does base excision work?
Glycosylase creates apurinated/apyrimidated site --> endonuclease cleaves 5' and lyase cleaves 3' --> DNA pol fills in --> ligase rejoins
46
What disease causes tryptophan deficiency leading to pellagra symptoms due to no tryptophan to make B3?
Hartnup
47
Which cells have high telomerase activity?
Epidermal cells and WBC
48
What does disruption of Fas/FasL cause?
Increasing number of autoreactive leading to autoimmune disorders? Fas is what destroys them in the thymic medulla during negative selection
49
How does sunlight cause production of vitamin D?
Causes conversion of 7-dehydrocholesterol to cholecaciferol?
50
What does fabry present with and what accmulates?
Ceramide Trihexoside Angiokeratomas (rash on your lower abdomen), peripheral neruopathy, renal and CV sx
51
What gives elastin its elastic properties?
Crosslinking (lysine cross linked) Elastin is not hydroxylated (collagen is not)
52
What is the primary source of glucose after 12-18 hours of fasting?
Gluconeogenesis
53
Why do you get cataracts from galactose enzyme deficiencies?
Due to aldose reductase converts galactose to galactitol which accumulates in the eye and causes cataracts?
54
What causes hemolytic anemia and posterior column, spinocerebellar tract demyelination?
Vitamin E deficiency
55
What is needed for the first step of urea cycle (ie positive regulator thing)?
N-acetylgluamate (activates carbamoyl phosphate synthease I)
56
What is the major source of nitrogen in urea cycle?
Aspartate
57
Where are promoters and where are enhancers/repressors?
Promoters can be anywhere Enhancers/repressors can be anywhere
58
What removes RNA primers?
DNA Pol I
59
What the lactose test for lactase deficiency?
Hydrogen breath increased and stool pH decreased from
60
What is the difference between Vit B12 and Vit E difference?
B12: megaloblastic anemia, and does corticospinal tract E: hemolytic anemia and does not do cortiscospinal tract
61
Which part tRNA binds amino acid?
3' where the CCA is
62
What is H1?
Outside nucleosome and helps to package nucleosomes into more compact structures by binding and linking dna between adjacent nucleosomes
63
Where does PPP occur?
Cytoplasm
64
What type of channel does CFTR encode?
ATP gated Cl channel
65
How does CFTR affect ENaC?
Inhibits ENac to dec Na absorption
66
What is the NaCl nasal mucosa test in CFTR?
Can apply isotonic NaCL to nasal mucosa and measure electrical difference between mucosa and interstitium: person with CF will show more negative difference due to inc Na absorption
67
What happens with FMR1 in fragile x?
Affects methylation and expression of FMR1 gene
68
What is southwestern blot?
Use double stranfded DNA to detect DNA binding protein
69
How do glucagon and epinephrine increase glycogenylosis?
via cAMP
70
How does active muscle increase glyocgenolysis?
Via Ca
71
What does 16s do?
Binds shine delgarno and initiates protein synthesis?
72
Why is fructose rapidly metabolized by the liver?
Because it bypasses the regulation of PFK-1 (rate limiting step)
73
How is glucose metabolized to fructose?
Glucose --> sorbitol --> fructose
74
What is the mTOR pathway?
Receptor --> tyrosine kinase --> PI3K --> AKT --> mTor to nucleus
75
What happens when there is abserrant serine and threonine phosphorylation of insulin tyrosine kinase?
Insulin resistance Can occur in presence of TNF-alpha, catecholamines, glucagon, GC
76
What is JAK/STAT pathway used by?
GH, prolactin, cytokines It is receptor associated tyrosine kinase
77
What is MAP kinase pathway?
Insulin, IGF, FGF, PDGF, EGF It is intrinsic tyrosine kinase
78
What two things can't use ketones for energy?
Liver and RBC
79
What breaks down very long chain FA, branched FA (phytanic acid)?
Peroxisomes
80
What presents with trouble releasing handshake/doorknob, gonadal atrophy, frontal balding, cataracts?
Myotonic dystrophy
81
What converts pro carcinogens to carcinogens?
CYP (microsomal monooxygenase)
82
Where is alanine's ammonia group to transfered to?
Alpha ketoglutrate
83
What is seen with genomic imprinting?
Methylation of DNA since it silences the gene
84
What do the bisophosphatases (FBPases 1 & 2) promote?
Gluconeogenesis (FBPase 2 converts fructose 2,6 bisphosphate to fructose 6 phosphate)
85
What does fructose 2,6 bisophosphate do?
Activates PFK-1 and promotes glycolysis (lots of 2,6 made when there is a lot of glucose) Insulin promotes fructose 2,6 bisophosphate formation
86
What does alanine get converted to?
Pyruvate
87
What is a liver specific enzyme that promotes TG breakdown?
Glycerol kinase (uses glycerol for TG breakdown and phosphorylates so that it can make glycerol 3 phosphate then DHAP - a glycolysis intermediate)
88
What does isoniazid cause?
Peripheral neuropathy due to decreased B6 GIVE PLP!
89
What does homocystinuria present with?
Kyphoscoliosis, lens subluxation, intellectual disability, osteoporosis, tall, THROMBOSIS, ATHEROSCLEROSIS

USMLE Step 1 Quick Notes (17 decks)

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