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Y Biochemistry 2 > 100 Semifinal Past Paper Questions > Flashcards

100 Semifinal Past Paper Questions Flashcards

1
Q

Which one of the following substrates cannot contribute to net gluconeogenesis in mammal liver?

  • alanine
  • palmitate
  • alpha ketoglutarate
  • glutamate
  • pyruvate
A

Palmitate

(only the odd-chain fatty acids can produce propionyl-CoA, which is the only possible glucogenic part of fatty acids)

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2
Q

Glycolysis in the erythrocyte produces pyruvate that is further metabolized to

  • CO2
  • lactate
  • glucose
  • hemoglobin
  • ethanol
A

lactate

(no MTC in RBC’s)

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3
Q

An enzyme used in both glycolysis and gluconeogenesis:

  • hexokinase
  • glucose 6-phosphatase
  • 3-phosphoglycerate kinase
  • phosphofructokinase-1
  • pyruvate kinase
A

3-phosphoglycerate kinase

(one of the reversible steps of glycolysis)

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4
Q

Which steps of gluconeogenesis are irreversible? (MULTIPLE ANSWERS)

  1. conversion of fructose-6 phosphate to fructose 1,6 bisphosphate
  2. conversion of glucose-6 phosphate to glucose
  3. reaction catalyzed by pyruvate kinase
  4. conversion of pyruvate to phosphoenolpyruvate
  5. reaction catalyzed by phosphoglycerate kinase

A: 2, 4 B: 1, 2, 4 C: 2,4,5 D: 2,3,4 E: 2

A

A: 2, 4

(not 100% sure, but many of the irreversible rxns are only for glycolysis, and the reversible rxns are from either pathway)

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5
Q

An example of an eicosanoid hormone is:

  • Testosterone
  • Epinephrine
  • Thyroxine
  • Thromboxane
  • Retinoic Acid
A

Thromboxane

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6
Q

Arrange the following reactions in the other that they take place in glycolysis:

  1. conversion of fructose-6-phosphate to fructose-1,6-bisphosphate
  2. conversion of 3 phosphoglycerate to 2 phosphoglycerate
  3. reaction catalyzed by pyruvate kinase
  4. reaction catalyzed by hexokinase
  5. reaction catalyzed by phosphoglycerate kinase

A: 4,1,5,2,3 B: 4,1,2,5,3 C: 4,1,3,2,5

D: 1,5,2,4,3 E: 1,4,5,2,3

A

A: 4,1,5,2,3

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7
Q

Which enzyme catalyzes the first ATP producing step of glycolysis?

  • phosphofructokinase 1
  • hexokinase
  • pyruvate kinase
  • phosphoglycerate mutase
  • phosphoglycerate kinase
A

phosphoglycerate kinase

(pyruvate kinase is 2nd ATP-producing step)

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8
Q

If glucose is labeled with 14C at C-1 (the aldehyde carbon) were metabolized in the liver, the first radioactive pyruvate formed would be labeled in:

  1. its carboxyl carbon
  2. its carbonyl carbon
  3. its methyl carbon
  4. both 1 and 3
  5. all 3 carbons
A

methyl carbon*

(not 100% sure, basing this on page 545 of Lehninger)

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9
Q

Lipoprotein lipase hydrolyzes triacylglycerols of the following lipoproteins: (multiple answers)

  1. VLDL
  2. nascent chylomicron
  3. mature chylomicron
  4. chylomicron remnant
  5. IDL

A: 3,5 B: 1,3,5 C: 2,3,4

D: 1,3 E: all

A

D: 1, 3

(requires ApoC-II)

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10
Q

The amount of which enzymes increases following a carbohydrate-rich meal:

  1. Acetyl-CoA Carboxylase
  2. Fatty Acid Synthase
  3. ATP-Citrate Lyase
  4. Glucose-6-Phosphate Dehydrogenase
  5. Malic Enzyme

A: 1,4,5 B: 1,2 C: 1,2,3 D: 2,4,5

E: all listed enzymes

A

E: All listed enzymes

(taken directly from Tretter lecture on lipids that NADPH producers are activated by insulin and carbs, and so are the fatty acid synthesizing enzymes)

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11
Q

Which of the following is(are) true of the beta-oxidation of long-chain fatty acids?

  1. the enzyme complex that catalyzes the reaction contains biotin
  2. FADH2 serves as an electron carrier
  3. NADH serves as an electron carrier
  4. Oxidation of an 18-carbon fatty acid produces six molecules of propionyl-CoA
  5. Oxidation of a 15-carbon fatty acid produces at least one propionyl-CoA

A: 3,5 B: 1,2,3 C: 1,2,5

D: 2,3,4 E: 2,3,5

A

E: 2,3,5

(propionyl-CoA produced only by odd chain fatty acids. biotin is part of carboxylases, important in FA synthesis)

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12
Q

The enzyme system for adding double bonds to saturated fatty acids requires all of the following except:

  • molecular oxygen (O2)
  • cytochrome b5
  • ATP
  • NADH
  • a mixed-function oxidase
A

ATP

(referring to Stearoyl-CoA desaturase aka delta-9-desaturase)

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13
Q

Which of the following pathways involve mitochondrial NADH production?

  1. citrate
  2. beta-oxidation of fatty acids
  3. purine de novo synthesis
  4. pyrimidine de novo synthesis

A: 1,2,4
B: 1,2
C: 1,2,3
D: 1,3
E: 2,4

A

A: 1,2,4

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14
Q

Which of the following statements is not true of the pathway by which purine nucleotides are synthesized?

  • the amino acid glycine is one of the precursors
  • deoxyribonucleotides are formed from 5-phosphodeoxyribosyl 1-pyrophosphate
  • inosinate is the purine nucleotide that is the precursor of both adenylate and guanylate
  • CO2 is required for one of the steps in the pathway
A

deoxyribonucleotides are formed from 5-phosphodeoxyribosyl 1-pyrophosphate

(deoxynucleotides come from ribonucleotide reductase rxn of nucleotide diphosphates -> deoxynucleotide diphosphates)

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15
Q

Which of the following compounds will be reduced by ribonucleotide reductase?

  • TMP
  • UMP
  • dUDP
  • UDP
  • UTP
A

UDP

(must be a nucleotide diphosphate for RR! )

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16
Q

Which of the following states result in hyperuricemia?

  1. Deficiency of glucose-6-phosphatase
  2. Deficiency of hypoxanthine-guanine-phosphoriboysyl transferase
  3. Cancer patients after chemo- and radiation therapy
  4. Deficiency of orotate-phosphoribosyl transferase
  5. Deficiency of PRPP-amidotransferase

A: 1,4,5 B: 1,2,3 C: 3,4,5

D: 1,2 E: 3,4

A

B: 1, 2, 3

(von Gierke disease leads to high Ri5P, HPRT used fo purine salvage rxns, and chemotherapy drugs lead to DNA breakdown and overproduction of purines. other causes: fructose intolerance/phosphate trap, heavy exercise, and PRPP overproduction via mutation and PRPP synthase allosteric inhibition site)

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17
Q

Per os administration of uridine is a choice of treatment in case of…

  1. UMP synthase deficiency
  2. Ornitine transcarbamoylase deficiency
  3. Gout if allopurinol treatment causes orotic aciduria
  4. Solid tumors during 6-aza-uridine treatment

A: 2 B: 1,2,3,4 C: 1,4

D: 1,3 E: 2,3

A

B: 1,2,3,4

I don’t know why, this past paper says it and so far everything else they’ve done has been right

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18
Q

Transamination of the following amino acids results in formation of citric acid cycle intermediates:

  1. alanine
  2. aspartate
  3. glycine
  4. glutamate

A: 1,2,3 B: 1,3 C: 2,4

D: 4 E: 1,2,3,4

A

C: 2,4

alanine and glycine can be transformed into pyruvate

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19
Q

Which of the following intermediates directly provide N atoms to form nucleotide bases?

  1. Amido group of Gln
  2. Amino group of Glu
  3. Asp
  4. Gly
  5. NH3

A: 1,3,4 B: 4,5 C: 1,2,3

D: 2,3,5 E: 1,3

A

A: 1,3,4

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20
Q

Select the enzymes involved in the pyrimidine salvage reactions?

  1. Thymine phosphorybosyl transferase
  2. Uridine-cytidine kinase
  3. Deoxycytidine kinase
  4. OMP decarboxylase

A: 2,3 B: 2,4 C: 1,2,3

D: 1,4 E: 1,2

A

A: 2,3

OMP decarboxylase involved in pyrimidine biosynthesis

thymine salvage is done by thymidine kinase

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21
Q

What is the name of the enzyme converting inosine to hypoxantine?

  • Hypoxantine phosphorybosyl transferase
  • inosine phosphatase
  • purine nucleoside phosphorylase
  • inosine kinase
  • xantine oxidase
A

purine nucleoside phosphorylase

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22
Q

The product of the reaction catalyzed by adenosine deaminase is:

  • IMP
  • inosine
  • hypoxantine
  • urate
  • adenine
A

inosine

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23
Q

Which of the following intermediates can be converted to serine in a single step reaction?

  1. Pyruvate
  2. Some citric acid cycle intermediates
  3. Some ornithine cycle intermediates
  4. Gly
  5. Choline

A: 1,2,4,5 B: 2,3,4

C: 1,4,5 D: 3 E: 4

A

E: 4

Only Glycine and the glycolysis intermediate of 3phosphoglycerate (as far as this image shows) can do that in one step

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26
Q

Glutamate dehydrogenase catalyzes the following reactions:

  1. Incorporation of NH4+ into the alpha-ketoglutarate
  2. Oxidation of NADPH + H+
  3. ATP -> ADP + Pi
  4. Release of NH4+ from Glu
  5. Release of NH4+ from Gln

A: 1,2,4 B: 3,4,5

C: 1,3,5 D: 1,4

E: all

A

A: 1,2,4

Glu dehydrogenase usually produces alphaketoglutarate using NAD+, but can also go in the opposite direction in the presence of high ammonia concentration, using NADPH as a cofactor and taking in free ammonia to form Glu

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27
Q

The binding of glucagon to its receptor will lead to:

  • the deactivation of adenylate cyclase
  • the decativation of protein kinase A
  • the deactivation of glycogen phosphorylase
  • activation of phosphodiesterase
  • the activation of phosphorylase kinase
A

the activation of phosphorylase kinase

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28
Q

If a person’s urine contains unusally high concentration of urea, which of the following diets has he or she probably been eating recently?

  • Very high carbohydrate, very low protein
  • very low carbohydrate, very high protein
  • very high fat, very low protein
  • very high fat, high carbohydrate, no protein
A

very low carbohydrate, very high protein

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29
Q

Which metabolic pathways might operate simultaneously in long-term starvation in the liver?

  1. glycogen breakdown
  2. glycolysis
  3. glutamine synthesis
  4. ketone body synthesis
  5. fatty acid synthesis

A: 1,3,4 B: 2,3,4

C: 1,3 D: 3,4

E: 2,3

A

D: 3,4

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31
Q

Possible utilization of glucose in erthyrocytes includes:

  1. glycogenesis
  2. aerobic glycolysis
  3. anaerobic glycolysis
  4. pentose phosphate pathway
  5. glucoronic acid pathway

A: 2,4,5 B: 2,4

C: 1,2,4 D: 3,4

E: 1,2,5

A

D: 3,4

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32
Q

Protein Kinase A:

  • converts cAMP to ATP
  • converts ATP to cAMP
  • activates glyocgen synthase
  • activates glycogen phosphorylase
  • deactivates glycogen synthase
A

deactivates glycogen synthase

(for glycogen phosphorylase, PKA only activates the glycogen phosphorylase kinase that then activates glycogen phosphorylase)

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34
Q

Which of the following statements are false?

  1. Insulin activates glycolysis in liver through decreasing fructose-2,6-bisphosphate levels
  2. epinephrine activates glycolysis in liver through increasing fructose-2,6-bisphosphate levels
  3. Epinephrine activates glycolysis in the heart through increasing fructose-2,6-bisphosphate levels
  4. Glucagon inhibits glycolysis in liver through decreasing fructose-2,6-bisphosphate levels
  5. Glucagon inhibits glycolysis in muscle through decreasing fructose-2,6-bisphosphate levels

A: 2,4,5 B: 1,2,5

C: 1,2,4 D: 1,3,5

E: 4,5

A

B: 1,2,5

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35
Q

Select the coenzymes needed for fatty acid synthesis: (multiple answers)

  1. CoA
  2. NADP
  3. FAD
  4. NAD
  5. Biotin
A

1,2,5

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36
Q

Select the compounds which are not ketone bodies: (multiple answers)

  1. Dihydroxyacetone
  2. acetoacetone
  3. beta hydroxybutyrate
  4. alpha hydroxibutryate
  5. oxaloacetate
A

1,4,5

are NOT ketone bodies

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37
Q

Select the correct order of enzymes or transporters operating in the disposal of excess cholesterol from the human body:

  • ABCA1 / LCAT / LDL / IDL / BSEP
  • ABCA1 / LCAT / LDL / VLDL / BSEP
  • ACAT / ABCA1 / HDL / LDL / BSEP
  • ABCA1 / LCAT / HDL / CETP / LDL
  • ABCA1 / ACAT / LCAT / HDL / LDL
A
  • ABCA1 / LCAT / HDL / CETP / LDL
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38
Q

Where is the 3-hydroxy 3-methyl glutaryl-Coa reductase localized within the cell?

  • in the free cytosol
  • in the membrane of the endoplasmic reticulum
  • in the matrix of mitochondria
  • in the inner membrane of mitochondria
  • in the outer membrane of mitochondria
A

in the membrane of the endoplasmic reticulum

needs to be to sense cholesterol concentration, but actual cholesterol synthesis takes place in cytosol

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39
Q

Which metabolic pathway uses the reaction catalyzed by 3-hydroxy-3-methyl glutaryl-CoA reductase?

  • glycolysis
  • synthesis of ketone bodies
  • oxidation of fatty acids
  • synthesis of fatty acids
  • synthesis of cholesterol
A

synthesis of cholesterol

(ketone bodies use HMG-CoA lyase)

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40
Q

The induction of which proteins causes a decrease in the number of LDL receptors? (multiple answers)

  1. SRE
  2. SREBP
  3. SCAP
  4. Insig
  5. Idol
A

4,5

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41
Q

Which cells express LXR? (multiple answers)

  1. hepatocyte
  2. enterocyte
  3. macrophage
  4. adipocyte
  5. smooth muscle cell
A

All of them!

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42
Q

Which statements are true regarding lecithin cholesterol acyl transferase? (multiple answers)

  1. It is one of the enzymes of cholesterol synthesis
  2. It forms cholesterol esters
  3. It is localized in the membrane of the ER
  4. Apo A1 is its activator
  5. It is active in the phosphorylated
A

2,4

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43
Q

Rearrange these in the correct order of the enzymes in the de novo synthesis of orotic acid:

  1. Carbamoyl-phosphate synthetase
  2. Dihydroorotase
  3. Asp transcarbamoylase
  4. Dihydroorotate dehydrogenase
A

1,3,2,4

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44
Q

Regulation of de novo AMP synthesis involves: (multiple answers)

  1. allosteric activation by GMP
  2. allosteric AMP
  3. availability of PRPP
A

2,3

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45
Q

Lesch-Nyhan syndrome can result from deficiency of: (one answer)

  • hypoxanthine-guanine (HGPRT) phosphoribosyl transferase
  • UMP synthase
  • adenosine deaminase
  • ornitine transcarbamoylase
  • xanthine oxidase
A

HGPRT

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46
Q

Which of the following enzyme deficienciesmight lead to severe immune deficiency?

  • hypoxanthine-guanine (HGPRT) phosphoribosyl transferase
  • UMP synthase
  • adenosine deaminase
  • ornitine transcarbamoylase
  • xanthine oxidase
A

adenosine deaminase

47
Q

Which of the following conditions cannot cause orotic aciduria?

  • Deficiency of UMP synthase
  • allopurinol treatment
  • 6-aza-uridine treatment
  • ornithine transcarbamoylase deficiency
  • all of the above can lead to orotic aciduria
A

all of the above can lead to orotic aciduria

48
Q

Select the cytochrome P450 isoenzymes! (multiple answers)

  1. side chain cleavage enzyme
  2. 21-hydroxylase
  3. 11-beta-hydroxy-steroid dehydrogenase
  4. 17-hydroxylase
  5. 17-hydroxy-steroid dehydrogenase
A

1,2,4

(the steroid dehydrogenases aren’t)

49
Q

Which enzymes are not requiredfor synthesis of estrogens starting from cholesterol? (multiple answers)

  1. 17-hydroxylase
  2. 21-hydroxylase
  3. 11-hydroxylase
  4. aromatase
  5. side chain cleavage enzyme
A

2,3

50
Q

Which statements are valid for N-acetyl glutamate? (multiple answers)

  1. its concentration depends on the concentration of arginine
  2. its concentration depends on the concentration or ornithine
  3. the activator of carbamoyl phosphate synthetase I
  4. activator of glutaminase
  5. activator of ornithine transcarbamoylase
A

1,3

51
Q

Select the valid statements: (multiple answers)

  1. Citrullin is an intermediate in the urea cycle
  2. Citrullin is a precursor of the denovo arginine biosynthesis
  3. Urea may be produced by the kidney
  4. Arginine may be produced by the kidney
A

1,2,4

52
Q

What is true among the following statements concerning the phosphorylation of fructose-6-P? (multiple answers)

  1. Fructose-6-P is phosphorylated by ATP to fructose 1,6 bisphosphate
  2. phosphorylation of fructose-6-P is catalyzed by phosphofructokinase 1
  3. phosphorylation of fructose-6-P is a reversible process
  4. phosporylation of fructose-6-P is stimulated by cyanide
A

1,2

53
Q

Which of the following statments about the pentose phosphate pathway is correct?

  • it provides precursors for the synthesis of nucleotides
  • it is a reductive pathway, it consumes NADH
  • it generates 36 moles of ATP per mole of glucose consumed
  • it is present in plants, but not animals
A

it provides precursors for the synthesis of nucleotides

54
Q

Protein kinase A:

  • activates phosphorylase kinase
  • deactivates phosphorylase kinase
  • activates glycogen phosphorylase
  • deactivates glycogen phosphorylase
  • glucokinase
A

activates phosphorylase kinase

(that one answer really was just “glucokinase”…)

55
Q

Which of the following statements are true for the metabolism of glutamine after 48 hours of starvation?

  1. glutamine is mainly synthesized in the brain
  2. there is an internsive release of glutamine from the skeletal muscle
  3. most of the glutamine is taken up by liver cells
  4. there is a net release (release > uptake) of glutamine from the liver cells
  5. most of glutamine is taken up by the kidney
A

2,3

56
Q

Possible utilization of glucose in hepatocytes includes (multiple answers)

  1. aerobic glycolysis
  2. pentose phosphate pathway
  3. glycogenesis
  4. glucoronic acid pathway
  5. anaerobic glycolysis
A

1,2,3,4

57
Q

Epinephrine triggers an increased rate of glycogen breakdown in muscle by causing:

  • activation of hexokinase
  • activation of phosphofructokinase-1
  • conversion of glycogen phosphorylase b to glycogen phosphorlyase a
  • the Pasteur effect
A

conversion of glycogen phosphorylase b to glycogen phosphorlyase a

58
Q

What is true for the Cori cycle (multiple answers)

  1. Liver can take up lactic acid from the circulation
  2. our body produces a lot of lactic acid even in resting state
  3. the maintenance of the cycle requires energy
  4. the cycle links 2 types of cells (tissues) through the blood circulation
A

1,3,4

59
Q

In anaerobic muscle preparation, lactate formed from glucose labeled in C-3 and C-4 would be labeled in:

  • all 3 carbon atoms
  • the carboxyl carbon atom only
  • the carbon atom carrying the OH only
  • the methyl carbon atom only
  • the methyl and carboxyl carbon atoms
A
  • the carboxyl carbon atom only
60
Q

Which statements are true for alpha amylase? (multiple answers)

  1. It is produced by pancreas and salivary glands
  2. It cleaves alpha-1,4 and alpha-1,6 bonds at the end of the glycogen chain
  3. its function is not affected by the acidic pH of the gastric juice
  4. it does not cleave disaccharides
  5. amylopectin is a substrate for amylase
A

1,4,5

61
Q

Which of the following transport mechanisms are involved in the absorption of glucose in the intestine? (multiple answers)

  1. Na+ ions - glucose transporter
  2. GLUT 4
  3. Insulin-dependent transport
  4. GLUT 2
  5. Glucose transport with low Km
A

1,4

62
Q

Insulin is an example of a(n) _______ hormone

  • peptide
  • catecholamine
  • steroid
  • eicosanoid
  • None of the above
A

peptide

63
Q

Which lipoprotein carries cholesterol to the extrahepatic tissues?

  • chylomicron?
  • HDL?
  • IDL?
  • LDL?
  • VLDL?
A

LDL

64
Q

Free fatty acids in the bloodstream are:

  • bound to hemoglobin?
  • carried by the protein serum albumin?
  • freely soluble in the aqueous phase of blood?
  • nonexistent; the blood does not contain FFA?
  • present at levels that are independent of epinephrine?
A

carried by protein serum albumin

65
Q

Lipoprotein lipase acts in:

  • hydrolysis of TAGs of plasma lipoproteins to supply fatty acids to various tissues?
  • intestinal uptake of dietary fat?
  • intracellular lipid breakdown of lipoproteins?
  • lipoprotein breakdown to supply needed amino acids?
  • none of the above?
A

hydrolysis of TAGs of plasma lipoproteins to supply fatty acids to various tissues

66
Q

The role of hormone-sensitive TAG lipase is to:

  • Hydrolyze lipids stored in the liver?
  • hydrolyze TAGs stored in adipose tissue?
  • hydrolyze membrane phospholipids in hormone-producing cells?
  • synthesize TAGs in the liver
  • synthesize lipids in adipose tissue
A

hydrolyze TAGs stored in adipose tissue

(mobilizes stored fats, inhibited by insulin)

67
Q

Which of the statements about TAG synthesis is correct?

  • phosphatidate is not on the pathway of TAG synthesis
  • mammals are unable to convert carbohydrates into TAG
  • insulin stimulates conversion of dietary carbs into TAG
  • humans can store more energy in glycogen than TAG
A

Insulin stimulates conversion of dietary carbohydrates into triacylglycerols

68
Q

The function of the NPC1L1 transporter is: (one answer)

  • to pump out bile salts into biliary capillaries
  • to pump out bile salts into the epithelial intestinal cells
  • to pump in cholesterol into the epithelial intestinal cells
  • to pump out cholesterol into the biliary capillaries
  • to pump out either cholesterol or bile salts into the biliary capillaries
A

to pump in cholesterol into the epithelial intestinal cells

69
Q

Which of the listed states is characterized by elevated concentration of free fatty acids in the blood plasma? (more than 1 answer)

  • following release of glucagon
  • prolonged fasting
  • after a meal
  • in the course of insulin therapy
A
  • following release of glucagon (see mobilization of TAG stored in adipose tissue slide)
  • Prolonged Fasting
70
Q

Which of the following statements are true for leptin? (more than one answer)

  • Leptins are secreted by adipocytes
  • Mice lacking leptin receptors are obese
  • High leptin level usually means large volume of adipose tissue
  • Leptins increase appetite
  • Leptins directly regulate insulin secretion
A
  • Leptins are secreted by adipocytes
  • Mice lacking leptin receptors are obese
  • High leptin level usually means large volume of adipose tissue
71
Q

Which of the following statements is not valid for lipoprotein lipase?

  • An enzyme with a low Km is present in the mammary gland
  • VLDL carries its cofactor
  • it degrades the majority of plasma triacylglycerols
  • its activity in adipose tissue increases in the fasting state
  • it is bound to the luminal surface of capillary endothelial cells
A

Its activity in adipose tissue increases in the fasting state

(adipose tissue has higher Km than heart tissue, allowing redirection of TAG’s from adipose tissue to the heart in fasting state. see Harper p. 257)

72
Q

Which factors in which sequence of the list reflects most completely the major route of cholesterol stored in extrahepatic tissue to its disposal in the intestine as bile salts?

  1. LDL
  2. HDL
  3. Cholesterolester transfer protein (CETP)
  4. lipoprotein lipase
  5. hepatic lipase
  6. LDL receptor
  7. Cyp7a
  8. ABCA1 transporter
A

8, 2, 3, 1, 6, 7

  • ABCA1 transporter
  • HDL
  • CETP
  • LDL
  • LDL receptor
  • Cyp7a
73
Q

Select the statements relevant to control mechanisms involved in the regulation of the plasma cholesterol level: (more than one answer)

  1. LDL receptors are under transcriptional control based on SREBP
  2. SREBP is released following cholesterol-dependent proteolysis of a precursor protein
  3. SREBP is a nuclear receptor that binds sterols
  4. LXR is a nuclear receptor that binds sterols
  5. Cyp7a is under transcriptional control based on LXR
  6. LXR prevents the release of cholesterol from the cells
A

1, 2, 4, 5

  • LDL receptors are under transcriptional control based on SREBP
  • SREBP is released following cholesterol-dependent proteolysis of a precursor protein
  • LXR is a nuclear receptor that binds sterols
  • Cyp7a is under transcriptional control based on LXR
74
Q

Lipoprotein Lipase hydrolyzes TAGs of the following lipoproteins: (more than one answer)

  • VLDL
  • nascent chylomicron
  • mature chylomicron
  • chylomicron remnant
  • HDL3
A
  • VLDL
  • mature chylomicron
  • HDL3 (this one seems weird, but according to answer sheet is correct)
75
Q

Which statements are valid for the scavenger receptors (SR)?

  1. SR’s are alternative specific receptors for the uptake of LDL
  2. Following binding of LDL to SRA, the ligand-receptor complex is internalized
  3. SRB1 is the major receptor for the uptake of oxidized LDL in macrophages
  4. SRA is under cholesterol-dependent transcriptional control
  5. SRB1 participates in the uptake of HDL-cholesterol in the liver
A

2, 5

  • Following binding of LDL to SRA, the ligand-receptor complex is internalized
  • SRB1 participates in the uptake of HDL-cholesterol in the liver
76
Q

Plasma level of unesterified fatty acids is increased: (multiple answers)

  • in starvation
  • in well-fed state
  • by glucagon
  • by ACTH
  • by insulin
A
  • in starvation
  • by glucagon
  • by ACTH
78
Q

What is true among the following statements concerning GLUT proteins?

  • Translocation of GLUT4 in adipocytes is insulin dependent
  • translocation of GLUT4 in adipocytes is glucagon dependent
  • translocation of GLUT4 is hormone insensitive
  • translocation of every GLUT protein is glucagon dependent
  • None of the above is true
A

Translocation of GLUT4 in adipocytes is insulin dependent

79
Q

Relationship between statements:

  1. The activity of glucokinase is increased in the presence of fructose-1-phosphate
  2. Glycolysis is accelerated in hereditary fructose intolerance in all tissues

A: Statement 2 is valid, but statement 1 is not

B: Neither statement is valid

C: Statements 1 and 2 are both valid, but there is no causative relation between them

D: Statements 1 and 2 are both valid, and 2 is the consequence of 1

E: Statement 1 is valid but statement 2 is not

A

E: Statement 1 is valid but statement 2 is not

80
Q

The enzyme system for adding double bonds to saturated fatty acids requires all of the following except:

  • molecular oxygen (O2)
  • cytochrome b5
  • ATP
  • NADH
  • a mixed-function oxidase
A

ATP

81
Q

Select the coenzymes needed for beta oxidation of fatty acids: (multiple answers)

  1. CoA
  2. NADP
  3. FAD
  4. NAD
  5. Thiamine-PP
A

1,3,4

82
Q

What enzyme is allosterically modulated by malonyl-CoA?

  • acylcarnitine translocase
  • carnitine palmitoyl transferase II
  • carnitine palmitoyl transferase I
  • acyl-CoA synthetase
  • ATP-citrate-lyase
A

CPT I

83
Q

Which of the following statements correctly describes the pathway by which purine nucleotides are synthesized:

  • the first enzyme in the path is aspratate transcarbamoylase (ATCase)
  • the purine rings are first synthesized, then condensed with ribose phosphate
  • the pathway occurs in plants and bacteria, not animals
  • purine deoxynucleotides are made by the same path as ribonucleotides, followed by reduction of the ribose moiety
  • the nitrogen in the purine base that is bonded to ribose in the nucleotide is derived originally from glycine
A

purine deoxynucleotides are made by the same path as ribonucleotides, followed by reduction of the ribose moiety

84
Q

Which substance is not involved in the production of urea from NH4+ in the urea cycle?

  • aspartate
  • ATP
  • ornithine
  • malate
  • carbamoyl phosphate
A
  • malate
85
Q

Select the valid statements: (multiple answers)

  1. S-adenosylmethionine provides methyl-group for the synthesis of epinephrine from norepinephrine
  2. S-adenosylmethionine provides methyl-group for the synthesis of phosphatidylcholine from phosphatidylethanolamine
  3. S-adenosylmethionine provides methyl-group for the synthesis of dTMP from dUMP
A

1,2

86
Q

Orotic aciduria is an inherited metabolic disease in which orotic acid (orotate) accumulates in the tissues, blood, and urine. The metabolic pathway in which the enzyme defect occurs is:

  • Pyrimidine synthesis
  • Pyrimidine breakdown
  • Purine synthesis
  • Purine breakdown
  • Epinephrine synthesis
A
  • Pyrimidine synthesis
87
Q

Glutamine, arginine, and proline:

  • may all be derived from a citric acid cycle intermediate
  • may all be derived from a glycolytic intermediate
  • may all be derived from a urea cycle intermediate
  • do not have a common precursor
A
  • may all be derived from a citric acid cycle intermediate
88
Q

Precursors for the biosynthesis of the pyrimidine ring system include:

  • glutamate, NH3, and CO2
  • glycine, glutamine, CO2 and aspartate
  • glycine and succinyl-CoA
  • carbamoyl phosphate and aspartate
A
  • carbamoyl phosphate and aspartate
89
Q

What is true among the following statements concerning drug conjugation:

  1. Gilbert’s syndrome is a conjugated hyperbilirubinemia
  2. Gilbert’s syndrome is an unconjugated hyperbilirubinemia
  3. Gilbert’s syndrome is an unconjugated hyperbilirubinemia, as the Crigler-Najjar syndrome
  4. Gilbert’s syndrome is a conjugated hyperbilirubinemia like the Dubin-Johnson syndrome
A

2,3

really awful wording here

90
Q

Which of the following amino acids are nutritionally essential for the human organism? (multiple answers)

  1. Isoleucine
  2. Serine
  3. Cysteine
  4. Phenylalanine
  5. Tryptophan
A

1,4,5

91
Q

Which of these amino acids are both ketogenic and glucogenic?

  1. isoleucine
  2. valine
  3. histidine
  4. arginine
  5. tyrosine
A

1,5

92
Q

What are the characteristics of regulation of gluconeogenesis in the kidney? (multiple answers)

  1. gluconeogenic enzymes are localized in the kidney medulla
  2. glucagon is the most important hormal signal for gluconeogenesis in the kidney
  3. acidosis stimulates gluconeogenesis in the kidney
  4. glutamine is an important precursor for gluconeogenesis
  5. pyruvate carboxylase is the most important regulatory enzyme of gluconeogenesis in the kidney
A

3,4

93
Q

Which of the following statements about the pentose phosphate pathway is incorrect:

  • it is principally directed towards the generation of NADPH
  • it requires the participation of molecular oxygen
  • it generates CO2 from C-1 of glucose
  • it is predominant in lactating mammary gland
  • it involves the conversion of aldohexose to an aldopentose
A

it requires the participation of molecular oxygen

94
Q

Which cytochrome does not participate in the biosynthesis of aldosterone from cholesterol? (multiple answers)

  1. P-450 SCC side chain cleavage enzyme
  2. P-450c17 (17 hydroxylase)
  3. P-450c21 (21 hydroxylase)
  4. P-450aro (aromatase)
A

2,4

95
Q

Zona glomerulosa of the adrenal cortex is the major site of synthesis of the following substances: (multiple answers)

  1. Renin
  2. angiotensin II
  3. corticosterone
  4. cortisol
  5. aldosterone
A

3,5

96
Q

Which mechanisms regulate the synthesis of testosterone?

  1. Leutinizing hormone (LH) activates the adenylate cyclase in Leydig cells
  2. Elevated cAMP level promotes the cleavage of the cholesterol side chain
  3. cholesterol side chain cleavage is inhibited by cAMP
  4. testosterone induces the release of gonadotropin-releasing hormone (GnRH) from the hypothalamus
A

1,2

97
Q

The rate of fatty acid synthesis is increased by: (multiple answers)

  1. Insulin
  2. long-chain fatty acids
  3. NADH
  4. glucagon
  5. citrate
A

1,5

98
Q

Select the correct statements: (multiple answers)

  1. The hormone-sensitive lipase (HSL) cleaves all 3 fatty acids from TAG
  2. Adipocytes express HSL
  3. the phosphorylated form of HSL is inactive
  4. the TAG-derived glycerol can not be phosphorylated in adipocytes
  5. the liver and the intestine express glycerol kinase
A

2,4,5

99
Q

Which proteins participate in reverse cholesterol transport?

  1. Apoprotein A-1
  2. LCAT
  3. Apoprotein B48
  4. Apoprotein C-II
  5. LPL
A

1,2

100
Q

Select all valid statements:

  1. Formation of tyrosine is an essential step in the physiological degradation of phenylalanine
  2. Phenylalanine may lose its amino group by a phenylalanine alpha-ketoglutarate transaminase
  3. Carbon skeleton of phenylalanine yields acetoacetate
A

1,3

101
Q

The human genetic disease phenylketonuria (PKU) can result from:

  • inability to convert phenylalanine to tyrosine
  • deficiency of protein in the diet
  • inability to catabolize ketone bodies
  • inability to synthesize phenylalanine
  • production of enzymes containing no phenylalanine
A

inability to convert phenylalanine to tyrosine

102
Q

Delta-aminolevulinic acid is formed from succinyl-CoA and _________ and is an intermediate in the biosynthesis of ___________

  • serine, sphingosine
  • serine, heme
  • acetyl-CoA, long chain fatty acids
  • alpha-ketoglutarate, glutamate and proline
  • glycine, porphyrin
A

glycine, porphyrin

103
Q

Which of the following enzymes directly connect intermediates of the citric acid cycle and the purine nucleotide cycle?

  1. Malate dehydrogenase
  2. alphaketoglutarate dehydrogenase
  3. citrate synthetase
  4. fumarase
  5. succinate dehydrogenase
A

1,3,4

104
Q

Which of the following reactions are related to the action of ribonucleotide reductase?

  1. Ribonucleotide monophosphate -> dirobonucleotide monophosphate (says something like that, hard to read)
  2. Oxidation of Cysteine-SH groups
  3. Reduction of Thioredoxin
  4. NADPH + H -> NADP+
  5. ATP -> AMP

A. 2,3,4 B: 1,2,3

C: 3,4,5 D: 1,3,4

E: 2,5

A

A: 2,3,4

105
Q

Which of the statements below is valid for Hereditary Orotic Aciduria?

  1. UMP Synthase is deficient
  2. Orotic acid in the diet is a successful treatment
  3. Purine salvage pathway is impaired

A: 1 B: 1,2

C: 1,3 D: 1,2,3

E: 3

A

A: 1

UMP Synthase is part of the pyrimidine synthesis pathway. And obviously including more orotic acid is not a good thing here.

106
Q

Which of the following enzymes is involved in pyrimidine de novo synthesis?

  • adenine phosphoribosyl transferase
  • cytosine phosphoribosyl transferase
  • Gln phosphorybosyl-pyrophosphate amidotransferase
  • hypoxanthine-guanine phosphoribosyl transferase
  • orotic acid phosphoribosyl transferase
A

orotic acid phosphoribosyl transferase

This is the step where pyrimidines get their ribose from PRPP, and UMP is formed

107
Q

The action of which of the following enzymes requires GTP or GDP?

  1. pyruvate carboxylase
  2. lactate dehydrogenase
  3. phosphoenolpyruvate carboxykinase
  4. succinyl CoA synthetase
  5. succinate dehydrogenase

A: 4 B: 3,5

C: 2,3,4 D: 1,4

E: 3,4

A

E: 3,4

108
Q

Which of the following statements are true for the metabolism of the kidney?

  1. phosphofructokinase activity is mainly localized in the cortex
  2. hexokinase activity is mainly localized in the medulla
  3. phosphoenol pyruvate carboxykinase activity is associated with the cortex
  4. acidosis-induced glutaminase activity is localized in the cortex
  5. glucose-6-phosphatase activity is found in the cortex

A. 1,2,4 B: 2,3,5

C: 1,4 D: 2,3,4,5

E: 2,4,5

A

D: 2,3,4,5

The medulla has few mitochondria and is more glycolytic, the cortex has more mitochondria and so can perform the TCA cycle but also has gluconeogenesis capacity that involves glutamine

(Straight from a Tretter lecture)

Y Biochemistry 2 (24 decks)

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