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UWorld Question Review > Biochemistry UWorld > Flashcards

Biochemistry UWorld Flashcards

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1
Q

Anticitrullinated peptides antibody highly specific for?

A

Rheumatoid arthritis

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2
Q

Anti DS DNA highly specific for…

A

SLE

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3
Q

Anti centromere antibodies highly specific for?

A

Crest syndrome

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4
Q

Polycistronic

A

1 mRNA codes for many proteins. One promoter. Common in prokaryotes, very rare in eukaryotes.

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5
Q

Indirect bilirubin uptake vs direct bilirubin output?

A

Unconjugated bilirubin uptake into hepatocytes is a passive process. Conjugated bilirubin is actively pumped out using MDR or OAT

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6
Q

Scurvy symptoms

A

Hemorrhagse, subperiosteal hematomas, bleeding, gingival swelling

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7
Q

Cofactor needed for ALA synthesis

A

B6 (pyridoxal phosphate)

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8
Q

Acute intermittent porphyria

A

Disease marked by painful abdomen, port-wine colored urine, polyneuropathy, psychological disturbances (anxiety), precipitated by drugs (phenobarbital, griseofulvin, phenytoin).

Caused by a defect in porphobilinogen deaminase which causes phorphobilinogen to build up, as well as ALA and coproporphyrinogen.

Treat with heme and glucose to inhibit ala synthase.

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9
Q

First step of heme synthesis

A

Glycine and succinyl coa form ALA with alas and b6

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10
Q

Elastin components, differences with collagen

A

Made of Glycine, alanine, valine, proline and lysine too.

Not as many residues are hydroxylated.

Extensive cross linkingis responsible for elastin being able to snap back into place.

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11
Q

Porphyria cutanea tardea

A

Late defect in heme synthesis which causes photosensitivity and tea colored urine. This is the most common porphyria.

Due to a deficiency in uroporphyrinogen decarbodylase, which causes uroporphyrinogen III to build up. No coproporphyrinogen made.

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12
Q

What type of receptor is the insulin receptor

A

Receptor tyrosine kinase.

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13
Q

How does TNA induce insulin resistance?

A

Activates serine kinases, which phosphorylate IRS-1 serine residues, this prevents tyrosine phosphorylation on IRS 1 by insulin.

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14
Q

Methylmalonyl CoA becomes?

A

Succinyl CoA via a mutase reaction with B12

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15
Q

Homocysteine becomes?

A

Methionine via homocysteine methyl transferase (uses THF/folate.

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16
Q

How are triglycerides used for energy?

A

They are used in glycolysis because glycerol can become Glyceraldehyde 3 P.

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17
Q

Amanitin does what…

A

Blocks RNA polymerase II.

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18
Q

Energy usage in states of fasting

12-18 hours?
18 hours +
1 week +

A

12- 18 hours. Glycogen is used
longer than 18 hours, gluconeogenesis is used
prolonged starvation, fatty acids are used.

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19
Q

Where is the receptor for thyroid hormone?

For TSH?

A

In the nucleus

TSH transmembrane

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20
Q

How are valine and isoleucine broken down?

A

Via alphaketoacid dehydrogenase (using the 5 cofactors used by PDH).

Become propionyl coA, then methyl malonyl coa (in a carboxylase reaction that requires biotin), then succinyl coa (in a mutase reaction that requires B12).

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21
Q

How is leucine broken down?

A

Becomes acetyl-coa, which is shunted into TCA.

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22
Q

Can RBCs use ketones?

A

No, because they lack mitochondria

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23
Q

How is sorbitol created and used

A

Glucose becomes sorbitol via aldose reductase and NADPH. Sorbitol then becomes fructose via sorbitol dehydrogenase (and NAD).

Schwann cells, retina, and kidneys have only aldose reductase. Lens has primarily aldose reductase.

Sorbitol is osmotically active.

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24
Q

Draw out galactose metabolism

A

Look at first aid

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25
Classic galactosemia
Deficiency of galactose uridyltransferase. Causes vomiting, lethargy, failure to thrive, when breastfeeding begins. Can also cause cataracts. Can lead to E.Coli sepsis in neonates******
26
Tumor lysis syndrome
Large numbers of cells destroyed quickly due to chemotherapy. Causes rapid increase in potassium, phosphate, nucleic acids in blood. Decrease risk with aggressive hydration. Decrease uric acid with allopurinol or rasburicase (which is urate oxidase) creates allantoin from uric acid to treat renal sxs of tumor lysis
27
Rasburicase
Urate oxidase creates allantoin from uric acid to decrease renal symptoms of tumor lysis syndrome
28
Probenecid
Uricosuric agent that decreases uric acid secretion. Only can be used in patient has good renal function, not in the case of uric acid nephropathy from tumor lysis syndrome
29
Kozak sequence
Upstream from AUG, key factor in translation initiation in eukaryotes.
30
Hexokinase
Takes G to G6P. Also takes fructose from diet and turns it into F6P for use in glycolysis.
31
Purpose of lactate?
To generate NAD from pyruvate if there is no O2 to regenerate NAD in the electron transport chain. NAD regeneration is necessary so glycolysis can continue.
32
Alkaptonuria
Darkening of tissues and turine due to a defect in homogentisate oxidase. Homogentisate cannot become maletoacetic acid
33
Where is rRNA synthesized?
In the nucleolus
34
How is insulin released
Glukokinase traps glucose and greates ATP in pancreatic beta cells. ATP closes K channels, cell depolarizes, ca comes in, insulin released.
35
Glucokinase deficiency
Maturity onset diabetes, causes a decrease in glucose trapped in cells, more in bloodstream
36
Which sugar is fed into glycolysis AFTER the rate determining enzyme PFK?
Fructose. Is turned into fructose 1 phosphate by fructokinase, then into glyceraldehyde and DHAP via aldolase B, Glyceraldehyde is then turned into G3P by triose kinase.
37
Function of JAK?
Kinase that activates STAT. Mutated in myelofibroses, essential thrombocytosis, and polycythemia vera.
38
Arginase deficiency
Arginine cannot become urea and OAA. ammonia builds up in the blood causing symtpoms like asterixis, somnolence, vomiting, cerebral edema.
39
Which enzymes use B1
Transketolase (used in reversible reactions of HMP shunt to create r5P g3p f6p), akg dehydrogenase, pyruvate dehydrogenase
40
What is transketolase used for?
To create r5p, g3p and f6p from ribulose 5 phosphate. Needs B1!
41
Thiamine necessary for?
Glucose utilization --> cannot give alcoholics glucose without B1.
42
Which reactions use BH4?
Phenylalanine hydroxylase, tyrosine hydroxylase, serotonin synthesis, and NO synthesis. BH4 reductase can cause PKU
43
Where are cortisol receptors located? Steps of cort activation during fasting
In cytoplasm bound to heat shock protein. When cort binds the receptors dimerize and translocate to the nucleus to initiate gluconeogenesis
44
Alanine Transaminase reaction, where does the NH3 group go?
Goes to alphaketoglutarate to form glutamate
45
Which steps of heme synthesis does lead inhibit?
ALAD and ferrochelatase
46
Regulator of pyruvate carboxylase in gluconeogenesis
Pyruvate becomes OAA via pyruvate carboxylase, which is activated by ACETYL COA
47
How to create cyanide poisoning
Use nitrites to create methemoglobin,
48
Symptoms of homocystinuria
Marfanoid habitus, bilateral lens subluxation, hypercoagulability. Can be caused by no B12 (can't become met), or no B6 (because B6 and serine are needed for cystathionine synthase)
49
Inheritance of familial hypercholesterolemia
Autosomal dominant
50
Function of beta-galactosidase
Turns lactose into galactose
51
Gibbs free energy negative? Postive?
If negative, products are favored. If positive, reactants are favored
52
How to synthesize niacin
Tryptophan with B6 and B2
53
Measles can be treated with
Vitamin A
54
What two types of reactions require pyridoxal phosphate?
Transamination and decarboxylation.
55
Hartnup disease
Loss of tryptophan in urine so niacin and 5HT can't be made. Tryptophan in urine
56
How does acyclovir work?
Guanosine nucleotide that stops viral chain elongation. Must be phosphorylated in viral cells.
57
Hox proteins do what?
DNA binding proteins
58
Energy usage at 1 week of starvation
FFAs are used to generate acetyl coa
59
Which cells cannot use ketone bodies for energy?
Red blood cells and liver cells.
60
Symptoms of PKU
Intellectual disability, seizures, fair skin, eczema
61
Do prokaryotes have introns?
Rarely. Also have only 1 origin of replication, where eukaryotes have multiple.
62
Which enzymes require biotin?
Acetyl CoA carboxylase (which takes acetyl CoA to malonyl CoA during fatty acid synthesis) Pyruvate carboxylase (which takes pyruvate to OAA in gluconeogenesis) Propionyl carboxylase (which takes amino acids (valine) into propionyl coa to methylmalonyl coa)
63
Pseudotumor cerebri symptoms
Headaches, papilledema, vomiting
64
Which enzymes require B1,B2,B3,B5, lipoate?
Alpha ketoglutarate dehydrogenase Pyruvate dehydrogenase Alphaketoacid dehydrogenase (turns long chain FA into propionate and breaks down valine/isoleucine)
65
D arm purpose? T arm purpose
AA charging (mediates correct recognition by correct aminoacyl trna synthetase) T arm for tRNA/ribosome binding
66
PEPCK cofactors
To turn OAA to PEP, must have GTP, which is made when succinyl CoA becomes succinate
67
Where are very long chain fatty acids metabolized?
In peroxisomes. No peroxisomes = zellweger's disease. Fatty acids accumulate, no myelin formation, hypotonia and seizures, hepatomegaly
68
GLUT 4
Responsible for INSULIN MEDIATED UPTAKE in skeletal muscles and adipocytes. Other gluts are insulin indepenent.
69
Haldane effect
Increased pO2 causes CO2 and H+ unloading
70
Mitochondrial DNA
Codes for oxidative enzymes and mitochondrial ribosomes and tRNA needed for mitochondrial synthesis.
71
Structure of HCG
Very similar to TSH, LH, FSH. Can cause activation of these organs
72
DNA polymerase 1
Has 5-3 exonuclease activity, can remove primer. Others are 3-5
73
Vitamin K does what...
Gamma carboxylates glutamate residues in liver
74
Radiation induces..
DS DNA breaks and free radical formation
75
Alpha helices in receptors
Have lots of nonpolar AA's to span membrane
76
How does aging affect collagen
Decreased synthesis, NOT decreased integrity or quality

UWorld Question Review (10 decks)

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