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Biochemistry Flashcards

0
Q

All the amino acids found in proteins are chiral except for: ______ which is not a chiral.

All amino acids in HUMAN proteins are which version of the enantiomer.

A

Glycine

L-configuration

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1
Q

What amino acid facilitates disulfide bonds?

A

Cysteine

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2
Q

All amino acids can act as buffers.

A

Repeat

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3
Q

What is one of the main differences between alpha helices and beta sheets.

A

Beta sheets usually have more than one peptide chain but can have only 1 as in globular proteins.

Both of these secondary structures are marked by the presence of H-bonds.

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4
Q

Bonds in proteins based on protein structure level:

A

Primary - peptide bond
Secondary - hydrogen bond
Tertiary - disulfide bonds, hydrophobic interactions, hydrogen bonds, ionic interactions

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5
Q

What protein is responsible for Alzheimer’s

A

denatured, amyloid-beta protein. Disease is associated with abnormal processing of these proteins. A key component of these fibers is abnormal Tau protein.

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6
Q

What does 2,3 BPG do to hemoglobin?

A

It stabilizes de-oxyhemoglobin.

It is expelled if Hb is able to bind oxygen.

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7
Q

Carbon monoxide binds hemoglobin and stabilizes the R form (increasing Hb affinity for oxygen) so it shift the curve to the left.

A

Repeat.

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8
Q

What are the essential amino acids?

A

PVT TIM HALL
Lysine, Leucine
Threonine, Tryotophan, Arginine

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9
Q

What disease presents with dermatitis, diarrhea, and dementia

A

Pellagra - Niacin (B3) deficiency. It can result from poor dietary intake or the absence of enough Tryptophan to convert to niacin. In the 2nd scenario, a neutral amino acid renal transporter is usually the issue.

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10
Q

What is the hallmark of Maple Syrup Disease?

A

Maple syrup disease is a deficiency of branched alpha ketoacid dehydrogenase. It affects levels of isoleucine, Leucine, and valine.

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11
Q

in what cell type does Gs increase intracellular calcium?

A

In cardiac muscle via upregulation of adenlyl cyclase and increase in cAMP.

For endothelial cells, it is Gq that has this effect.

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12
Q

What genetic disease is associated with bilateral acoustic schwannomas? What other diseases are associated with this genetic disease?

A

NF2 - autosomal dominant - chromosome 22 - acoustic neuromas, meningiomas, gliomas, ependymomas.

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13
Q

What disease is associated with pigmented iris harmatomas?

A

NF 1 - cafe-au-lait spots, neural tumors

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14
Q

What is the inheritance pattern for:
Duchenne’s muscular dystrophy
Marfan’s
Neurofibromatosis

A

What is the inheritance pattern for:
Duchenne’s muscular dystrophy - X-linked recessive frame shift mutation like Hemophilia
Marfan’s - Autosomal dominant
Neurofibromatosis - Autosomal dominant

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15
Q

In what disease do people develop dark urine on standing?

A

Alkaptonuria - pts build up homogentisic acid which is in the pathway for tyrosine degradation. They may also develop arthralgias.

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16
Q

Hepatosplenomegaly, mental retardation, expected death by age 3 is concerning for…

A

Niemann-Pick Disease.

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17
Q

What enzyme converts glucose into glucose-6-phosphate?

A

Hexokinase

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18
Q

What is the deficiency in Von Gierke’s disease?

A

Glucose-6-phosphatase deficiency. This means they cannot free stored glycogen AND they cannot perform gluconeogenesis.

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19
Q

A deficiency of N-acetylglucosamine phosphotransferase is associated with what disease and what are the implications of this deficiency?

A

I-cell disease. The implication is that enzymes are exocytosed instead of being directed to the lysosome. This results because of failure of phosphorylation of mannose residues.

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20
Q

What amino acids are critical in the synthesis of thyroid hormone?

A

Tyrosine residues are required for iodide processing in the formation of thyroid hormone. By extension, a deficiency of phenylalanine could also result in hypothyroidism.

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21
Q

What enzyme is defective in SCID?

A

SCID is a deficiency of T and B cells. The enzyme deficiency is adenosine deaminase.

22
Q

What toxic exposure is associated with prolonged nitroprusside infusion or use?

A

Cyanide toxicity.
Nitroprusside gets converted to cyanide in the body and cyanide has a huge affinity for the mitochondrial cytochrome oxidase complex (due to Fe3+).

23
Q

How does arsenic exert its effect?

A

It inhibits lipoic acid which is a REQUIRED cofactors for Pyruvate dehydrogenase.

24
Q

What kind of RNA does RNA polymerase II make? What feared toxin inhibits RNA polymerase II?

A

RNA polymerase II makes mRNA. Alpha-amanitin poison inhibits RNA polymerase II from making mRNA and cause severe liver toxicity.

25
Q

What organ besides the liver carries out heavy gulconeogenesis?

A

The kidney. The rate limiting enzyme is fructose 1,6 bisphosphatase.

26
Q

What is one of the major components of surfactant?

A

Phosphatidylcholine (lecithin).

27
Q

What is one of the major roles of Vit C?

A

It facilitates iron absorption which occurs in the duodenum and upper jejunum. Vit C (ascorbic acid) keeps iron in its reduced form.

28
Q

What is the mechanism of action of erythromycin and other macrolides?

A

It inhibits protein synthesis of prokaryotic (50s) ribosomes.

29
Q

Which leukotrienes contribute to increased bronchial tone in asthma?

A

Leukotriene C4,
Leukotriene D4
Leukotriene E4.
Pay attention to the letters! (C-E)

30
Q

What genetic defect in children is associated with cleft lip, extra digits, and extremely small eyes.

A

Trisomy 13 (Patau).

31
Q

How does aspirin work? Of what types of molecules does it inhibit formation?

A

Aspirin interrupts the arachidonic acid pathway. It inhibits the formation of prostaglandins and thromboxanes. It does this because arachidonic acid is a substrate for cyclooxygenase.

32
Q

What are the consequences of high levels of ammonia like in hepatic encephalopathy?

A

It depletes alpha-ketoglutarate

and increases glutamine

33
Q

How do statins work?

A

They act as a competitive inhibitor (increase apparent Km) of HMG CoA reductase. Statins also upregulate the expression of LDL receptors on the liver which increases LDL clearance from the bloodstream.

34
Q

What type of thalassemia which presents in a severe hemolytic manner is more common amongst people of Mediterranean descent.

A

Beta thalassemia.

35
Q

Angiokeratomas on the abdomen and extremities, anhydrosis, and acroparasthesias (burning sensation) are concerning for…

A

fabry’s. Build up ceramics trihexose.

36
Q

How does paclitaxel work?

A

It prevents microtubule depolymerization so cells stay stuck in mitosis.

37
Q

How does vincristine work?

A

Vincristine works in the M-phase of the cell cycle by binding tubulin (one of the components of microtubules) and preventing mitotic spindle formation. It is mainly used in Hodgkin’s and Non-Hodgkin’s lymphoma.

38
Q

How does bleomycin work and what are its side effects?

A

It intercalates DNA during the G2 phase and causes scission of DNA by an oxidative process. Its adverse effects are pulmonary - rales, cough, infiltration leading to fibrosis in the lung.

39
Q

How does 5-FU work?

A

It arrests cells in the S phase leading to impaired DNA synthesis. Specifically, it interferes with the conversion of deoxyuridylic acid to thymidylic acid.

40
Q

What do gut bacteria do to bilirubin?

A

Gut bacteria deconjugates bilirubin (which was conjugated in liver) and degrades it to urobilinogens. Thus, bilirubin must come in contact with the gut for urobilinogens to be created. In the setting of obstruction and renal excretion of conjugate bilirubin, this is not the case so urine urobilinogen excretion is deceased in the setting of obstruction. Note, however, that the vast majority of urobilinogens under normal circumstances are excreted in feces.

41
Q

What drugs act on microtubules? Remember the mnemonic.

A 
Microtubules Get Constructed Very Poorly.
Mebendazole,
griseofulvin,
Colchicine,
Vincristine,
paclitaxel
42
Q

What is the effect if thyroid hormone?

A

Thyroid hormone (pro-growth) promotes gluconeogenesis, glycogenolysis, and lipolysis.

It stimulates brain maturation, bone growth, beta adrenergic effects, basal metabolic rate (increased Na/K ATPase).

43
Q

What layer do atheromata form in the arteries?

What is usually synthesized by this layer?

A

Intima.

Prostacyclin and nitrous oxide by the endothelial cells to prevent plaque formation

44
Q

The initial test for HIV is ________

The confirmatory, more specific test is _______

A

ELISA - initial screen - antibody-antigen

Western - confirmatory, more specific - antibody-protein

45
Q

In 5 alpha reductase deficiency, there is ambiguous genitalia until puberty when there is masculinization of the genitals.

A

Repeat.

46
Q

Increased testosterone and increased LH together with increased estrogen in a female with a blind vagina suggest …

A

Androgen insensitivity syndrome. 46XY.

47
Q

What is diamond Blackfan anemia?

A

It is a pure, congenital red cell aplasia.

48
Q

What is Fanconi anemia?

A

DNA repair defect - these patients are especially sensitive to alkylating agents. It is most common cause of INHERITED APLASTIC ANEMIA and an important cause of acute amyloid leukemia in children. They can have abnormal or absent radii or thumbs, kidney malformations, Hypogonadism and HIGH levels of HbF.

49
Q

Where does the phosphorylation of mannose residues normally occur?

A

It occurs in the GOLGI!!!

Not the ER. It is the GOLGI! People with I-cell disease have restricted joint movement and coarse facial features.

50
Q

Itchy skin, diarrhea, beefy red tongue are concerning for…

An excess of this vitamin could lead to facial flushing.
What amino acid is important for the synthesis of niacin?

A

Pellagra. Niacin deficiency. Vitamin B3.

Tryptophan is important. This can be an issue in Hartnup disease where there is decreased tryptophan metabolism.

51
Q

What does PGI2 do?

A

PGI 2 (prostacyclin). Inhibits platelet aggregation and decreases vascular tone.

52
Q

Statins are great to lower cholesterol but isolated hypertriglyceridemia, consider using a fibrate.

A

Repeat

53
Q

In Prader willi, PATERNAL gene is GONE!

A

Repeat

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