Question 1

Lecture 53

Accepted Answer

Pyrimidine Metabolism

Question 2

UMP is the parent nucleotide for ___ and ___.

Accepted Answer

CTP and dTMP

Question 3

Formation of UMP is through ___ steps/reactions.

Accepted Answer

6

Question 4

Not all reactions are ___ in formation of UMP.

Accepted Answer

cytosolic

Question 5

UMP is not built on a PRPP donated ___.

Accepted Answer

ribosyl-5-phosphate

Question 6

PRPP donating ribosyl-5-phosphate is the ___ step in making UMP.

Accepted Answer

last

Question 7

UMP is forms to ___ before making CTP.

Accepted Answer

UTP

Question 8

Biosynthesis of carbamoyl phosphate is by ___.

Accepted Answer

CPS II

Question 9

CPS II works in the ___, and uses ___.

Accepted Answer

cytosol, glutamine

Question 10

Regulated step in pyrimidine synthesis is ___.

Accepted Answer

CPS II

Question 11

CPS II is actvated by ___.

Accepted Answer

PRPP

Question 12

Synthesis of UMP uses two multifunctional ___.

Accepted Answer

enzymes

Question 13

CAD is encoded by ___ gene(s).

Accepted Answer

1 gene

Question 14

Enzymes in CAD are ___, ___, and ___.

Accepted Answer

Carbamoyl phosphate synthase II, aspartate transcarbamoylase, and dihydroorotase.

Question 15

Enzymes in UMP synthase are ___ and ___.

Accepted Answer

orotate phosphoribosyltransferase and OMP decarboxylase

Question 16

___ donates C4-6 and N1 to the pyrimidine structure.

Accepted Answer

Aspartate

Question 17

___ donates C2 to the pyrimidine structure.

Accepted Answer

HCO3- (Bicarbonate)

Question 18

___ donates N3 to the pyrimidine structure.

Accepted Answer

Glutamine amide

Question 19

Hereditary orotic aciduria leads to anemia because of:

Accepted Answer

RBC synthesis’ high demand for DNA synthesis

Question 20

Hereditary orotic aciduria causes anemia and ___.

Accepted Answer

growth retardation

Question 21

UTP and CTP both negatively feedback to ___.

Accepted Answer

CPS II

Question 22

___ and ___ up-regulate CPS II.

Accepted Answer

ATP and PRPP

Question 23

Orotic Aciduria, Type I

Accepted Answer

Defective UMP synthase (both), autosomal recessive, orotic acid crystalluria, FTT, megaloblastic anemia, immunodeficiency

Question 24

Orotic Aciduria, Type II

Accepted Answer

Defective UMP synthase (orotidylate decarboxylase only), autosomal recessive, orotidinuria and orotic aciduria, megaloblastic anemia, treatable with oral uridine

Question 25

Ornithine Transcarbamoylase Deficiency

Accepted Answer

Defective OTC, X-linked recessive, protein intolerance, hepatic encephalopathy, mild orotic acidura

Question 26

UMP to UTP is through two ___ steps.

Accepted Answer

phosphorylation steps (ATP donor)

Question 27

CTP Synthase

Accepted Answer

Catalyzes synthesis of CTP from UTP by substituting keto group for amino group

Question 28

The nitrogen donor in CTP synthase is ___, releasing ___.

Accepted Answer

glutamine, releasing glutamate

Question 29

The phosphate donor group in CTP synthase is ___.

Accepted Answer

ATP

Question 30

Pyrimidine nucleosides can be salvaged by ___.

Accepted Answer

ATP-requiring kinases

Question 31

Pyrimidine nucleoside salvaging kinases are:

Accepted Answer

uridine-cytidine kinase, thymidine kinase, deoxycytidine kinase

Question 32

Nucleoside 5’-Diphosphate Reductase (Ribonucleotide Reductase)

Accepted Answer

Catalyzes synthesis of 2’-deoxyribonucleotide from ribonucleotide (DNA to RNA)

Question 33

___, ___, and ___ can be formed directly from its precursors by ribonucleotide reductase and phosphorylation.

Accepted Answer

dATP, dGTP, and dCTP

Question 34

dTTP is not directly synthesized to prevent:

Accepted Answer

accidental incorporation of dUDP into DNA

Question 35

Synthesis of dTTP can be from precursors ___ or ___.

Accepted Answer

CDP or UDP

Question 36

CDP → ___ → ___ → ___ → ___ →→ dTTP

Accepted Answer

CDP →dCDP → dCMP → dUMP → dTMP →→ dTTP

Question 37

UDP → ___ → ___ → ___ →→ DTTP

Accepted Answer

UDP → dUDP → dUMP → dTMP →→ dTTP

Question 38

Thymidylate Synthase

Accepted Answer

Catalyzes synthesis dTMP from dUMP, requires tetrahydrofolate

Question 39

Pyrimidine analogs can block ___.

Accepted Answer

DNA synthesis

Question 40

Cytosine Arabinoside

Accepted Answer

Leukemia & non-Hodkin lymphoma therapy, AraC → AraCMP → AraCTP into DNA, inhibits strand elongation

Question 41

3’-azido-3’-deoxythymidine (AZT)

Accepted Answer

AZT triphosphate, inhibits HIV DNA polymerase

Question 42

Methotrexate is a structural analog of ___.

Accepted Answer

folic acid

Question 43

Methotrexate inhibits ___.

Accepted Answer

dihydrofolate reductase (synthesis of dihydrofolate from folate or regeneration of dihyrdofolate to tetrahydrofolate)

Question 44

___ cells are especially sensitive to dihyrdofolate reductase inhibitors (i.e. methotrexate).

Accepted Answer

Dividing

Question 45

β-aminoisobutyrate excretion measures ___.

Accepted Answer

DNA breakdown

MBC - Lecture 53

Pyrimidine Metabolism (Mock)

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