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Flashcards in 12. Biochem Deck (99):
1

What is the rate-limiting enzyme in purine synthesis? In pyrimidine synthesis?

purine: glutamine PRPP amidotransferase

pyrimidine: CPS2 (carbamoyl phosphate synthetase 2)

2

What are the sources of carbon in the synthesis of purines? (3) in pyrimidine synthesis? (2)

- purines: CO2, glycine, tetrahydrofolate
- pyrimidines: aspartate, CO2

3

Which medication inhibits each of the following enzymes?
- ribonucleotide reductase

hydroxyurea

4

Which medication inhibits each of the following enzymes? (2)
- dihydrofolate reductase

TMP, methotrexate

5

Which medication inhibits each of the following enzymes?
- thymidylate synthase

5-FU

6

Which medication inhibits each of the following enzymes?
- inosine monophosphate (IMP) dehydrogenase

mycophenolate

7

Which medication inhibits each of the following enzymes?
- PRPP amidotransferase

6-MP
- note this is the rate-limiting enzyme

8

What accounts for the positive charge of histones? What accounts for the negative charge of DNA?

histones: b/c made of lysine and arginine

DNA: negative b/c of phosphate groups

9

How does UV radiation damage DNA?

makes pyrimidine dimers (usually T-T) on the same strand of DNA --> makes "bulky" helix-distorting lesion

need repair via nucleotide excision repair

10

What amino acid is encoded by the most common start codon?

AUG --> methionine

11

What is the diff. b/w an intron and exon?

Intron: non-coding segment of DNA
Exon: coding sequences for specific protein products

12

Production of what enzyme is regulated by the lac operon?

b-galactosidase

13

What two proteins regulate the lac operon?

- CAP
- lac repressor

14

What 2 substrate conditions must be met for the lac genes to be transcribed?

- abundant lactose (removes repressor)
- low glucose (allows CAP to bind)

15

What enzyme matches amino acids to tRNA?

aminoacyl tRNA synthetase

16

What antibiotics are inhibitors of prokaryotic protein synthesis at the 30S ribosomal subunit?

- aminoglycoside
- tetracyclines

17

What antibiotics are inhibitors of prokaryotic protein synthesis at the 50S ribosomal subunit?

- chloramphenicol
- clindamycin
- macrolides
- linezolid

18

What enzymes convert glucose to glucose-6-phosphate?

hexokinase or glucokinase (only in liver and b-cells of pancreas)

19

What is the clinical consequence of a glycolytic enzyme deficiency?

hemolytic anemia

20

What enzymes are responsible for increasing and dereasing the intracellular levels of fructose-2,6-bisphosphate?

PFK-2 (fed): increase level of fructose 2,6-BP
FBPase-2 (fasting): decrease level of fructose 2,6-BP

21

What is the rate limiting enzyme in the glycolytic pathway?

phosphofructokinase-1

22

What irreversible enzymes are involved in gluconeogenesis (4)

1. pyruvate carboxylase (with biotin)
2. PEP carboxylase
3. fructose-1,6-bisphosphatase
4. glucose-6-phosphatase

23

What enzyme catalyzes the rate-limiting step in gluconeogenesis?

fructose-1,6-bisphosphatase

24

What is the rate limiting enzyme for glycogen synthesis? For glycogenolysis?

- glycogen synthase
- glycogen phosphorylase

25

Which enzyme converts G-6-P to glucose?

glucose-6-phosphatase

26

Which glycogen storage disease matches each of the following phrases?
- glycogen phosphorylase deficiency

McArdle

27

Which glycogen storage disease matches each of the following phrases?
- glucose-6-phosphatase

Von Gierke

28

Which glycogen storage disease matches each of the following phrases?
- lactic acidosis, hyperlipidemia, hyperuricemia (gout)

Von Gierke

29

Which glycogen storage disease matches each of the following phrases?
- a-1,6-glucosidase deficiency

cori

30

Which glycogen storage disease matches each of the following phrases?
- a-1,4-glucosidase deficiency

Pompe

31

Which glycogen storage disease matches each of the following phrases?
- cardiomegaly

pompe (infantile type)

32

Which glycogen storage disease matches each of the following phrases?
- diaphragm weakness leading to resp failure

pompe (adult type)

33

Which glycogen storage disease matches each of the following phrases?
- increased glycogen in liver, severe fasting hypoglycemia

Von Gierke

34

Which glycogen storage disease matches each of the following phrases?
- hepatomegaly, hypoglycemia, hyperlipidemia (normal kidneys, lactate, uric acid)

cori

35

Which glycogen storage disease matches each of the following phrases?
- painful muscle cramps, myoglobinuria with strenous exercise

McArdle

36

Which glycogen storage disease matches each of the following phrases?
- severe hepatosplenomegaly, enlarged kidneys

von gierke

37

What are the possible products of pyruvate? (4)

- acetyl-coa
- oxaloacetate
- lactate
- alanine

38

What are the two main nitrogen transporters in the blood?

- alanine
- glutamine

39

What are the major regulatory enzymes of the TCA cycle? (3)

- citrate synthase
- isocitrate dehydrogenase
- a-ketoglutarate dehydrogenase

40

What substances are known to inhibit the complexes of the electron transport chain?

- amytal
- rotenone
- MPP
- antimycin A
- cyanide (CN)
- azide (N3-)
- carbon monoxide (CO)
- hydrogen sulfide (H2S)

41

What substances can increase the permeability of the inner mitochondrial membrane, thereby decreasing ATP synthesis but increasing heat generation? (3)

uncoupling agents
- aspirin (high dose)
- thermogenin (in brown fat)
- 2,4-dinitrophenol

42

What is the rate-limiting step of the pentose phosphate pathway?

G6PD

43

Which tissues of the body use the pentose phosphate pathway? (4)

- RBCs
- liver
- adrenal cortex
- mammary glands

44

Explain why a deficiency of the enzyme that is the rate limiter for the HMP shunt can result in hemolytic anemia

G6PD deficiency
- decreased NADPH --> decreased reduced glutathione
- RBCs more susceptible to oxidative damage --> hemolysis

45

What are the symptoms of classic galactosemia?

- failure to thrive
- intellectual disability
- hepatomegaly
- jaundice
- infantile cataracts

46

What disorder is caused by a deficiency of each of the following enzymes?
- galactokinase

galactokinase deficiency

47

What disorder is caused by a deficiency of each of the following enzymes?
- aldolase B

fructose intolerance

48

What disorder is caused by a deficiency of each of the following enzymes?
- lactase

lactose intolerance

49

What disorder is caused by a deficiency of each of the following enzymes?
- galactose-1-phosphate uridyltransferase

classic galactosemia

50

What disorder is caused by a deficiency of each of the following enzymes?
- fructokinase

essential fructosuria

51

What is the primary energy source in a patient that has not eaten in 2 days?

fatty acids

52

What is the rate-limiting enzyme in ketone body synthesis?

HMG-CoA synthase

53

How does ethanol leads to hypoglycemia?

- increase NADH when you metabolize ethanol
- shunts pyruvate towards production of lactate, and oxaloacetate --> malate
- thus, pyruvate and oxaloacetate no longer available for gluconeogenesis

54

What are some of the hallmark features of kwashiorkor?

FLAMES
- fatty liver
- anemia
- malnutrition
- edema
- skin lesions

55

What deficiency causes familial hypercholesterolemia?

deficiency in LDL receptor

56

which apolipoprotein matches each of the following statements?
- activates LCAT

ApoA-1

57

which apolipoprotein matches each of the following statements?
- mediates chylomicron secretion

ApoB-48

58

which apolipoprotein matches each of the following statements?
- mediates VLDL secretion

ApoB-100

59

which apolipoprotein matches each of the following statements?
- cofactor for lipoprotein lipase

ApoC-II

60

which apolipoprotein matches each of the following statements?
- mediates uptake of remnant particles

ApoE

61

What is the rate-limiting enzyme for fatty acid synthesis

acetyl CoA carboxylase

62

What is the rate-limiting enzyme for beta-oxidation of fatty acids

carnitine acyl transferase 1

63

What is the rate-limiting enzyme for ketone body synthesis

HMG CoA synthase

64

What is the rate-limiting enzyme for cholesterol synthesis

HMG CoA reductase

65

What are the essential amino acids?

Private (PVT) TIM HaLL
- phenylalanine
- valine
- threonine
- tryptophan
- isoleucine
- methionine
- histidine
- leucine
- lysine

66

What amino acid is the precursor to the following?
- histamine

histidine

67

What amino acid is the precursor to the following?
- porphyrin, heme

glycine

68

What amino acid is the precursor to the following?
- NO

arginine

69

What amino acid is the precursor to the following?
- GABA

glutamate

70

What amino acid is the precursor to the following?
- S-adenosyl-methionine (SAM)

methionine

71

What amino acid is the precursor to the following?
- creatinine

arginine

72

A full-term neonate feeds poorly, is hyperactive, and has musty odor. What is the diagnosis?

PKU
- deficiency in phenylalanine hydroxylase or BH4

73

A patient with PKU should have a diet low in phenylalanine. What other dietary modification should a pt with PKU make? (2)

- high tyrosine diet
- BH4 supplementation

74

A middle-aged man has dark spots on his sclera, and has noted that his urine turns black when left sitting for a period of time. What is the diagnosis?

Alkaptonuria
- defect with homogentisate oxidase

75

What is the underlying cause of maple syrup urine disease?

deficiency of branched chain a-ketoacid dehydrogenase complex

76

What has been the most common clinical scenario of excess iron ingestion in the last 3 decades?

infant consuming iron-fortified vitamins (prenatal vitamins)

77

What are some of the clinical effects of zinc deficiency?

- delayed wound healing
- impaired immune response
- rash around eyes, mouth, nose, anus (acrodermatitis enteropathica)

78

What are some of the signs of hypocalcemia?

- tetany and neuromuscular irritability
- Chvostek sign
- Trousseau sign

79

What organs are primarily affected by excess of mercury?

kidney and brain

80

What vitamin in excess can cause hypercalcemia?

vitamin D

81

What are the symptoms of vitamin A toxicity

- visual impairment
- fatigue
- ataxia
- headache
- increased ICP (pseudotumor cerebri)
- alopecia

82

What clinical features would lead you to suspect that a patient has scurvy?

- sore spongy gums
- loose teeth
- hemorrhage (b/c fragile vessels)
- swollen joints (hemarthrosis)
- impaired wound healing

83

Vitamin C is necessary for the hydroxylation of which amino acids in collagen synthesis? (2)

- proline
- lysine

84

Which enzymes are used to convert cholecalciferol to calcitriol?

1. 25-hydroxylase (liver)
2. 1a-hydroxylase (kidney)

85

A patient presents with convulsions and irritability. What vitamin deficiency is causing these symptoms in this patient?

B6 (remember, B6 required for synthesis of GABA)

86

What type of anemia can be caused by folate or B12 deficiency?

megaloblastic anemia

87

Where is B12 absorbed into the circulation?

Terminal ileum

88

Which vitamin deficiency matches?
- peripheral neuropathy, glossitis

B12, B6

89

Which vitamin deficiency matches?
- neural tube defects

B9 (folate)

90

Which vitamin deficiency matches?
- dermatitis, diarrhea, dementia

B3 (niacin)

91

Which vitamin deficiency matches?
- megaloblastic anemia

B9 (folate), B12

92

Which vitamin deficiency matches?
- Pernicious anemia

B12

93

Which vitamin matches each of the following?
- used in oxidation/reduction reactions

B2 (FAD)
B3 (NAD, NADP)

94

Which vitamin matches each of the following?
- used in carboxylation reactions

Biotin (B7)
note: also vit K for gamma-carboxylation of glutamic acid

95

Which vitamin matches each of the following?
- used by pyruvate dehydrogenase and a-ketoglutarate dehydrogenase

B1 (thiamine)

96

Which vitamin matches each of the following?
- can be used to elevated HDL and lower LDL

B3 (niacin)

97

Which vitamin matches each of the following?
- deficiency can be caused by isoniazid use

B6

98

Which vitamin matches each of the following?
- cobalt is found within this vitamin

B12 (cobalamin)

99

Which vitamin matches each of the following?
- critical for DNA synthesis

B9 (folate), B12