MERP Biochemistry lecture 8

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What is the rate limiting step of DNA synthesis?

Regeneration of tetrahydrofolate

Formation of dCTP

Synthesis of dTMP (correct)

Conversion of dUDP to dTMP

Which enzyme is inhibited by Methotrexate?

Dihydrofolate reductase (correct)

Thymidylate synthase

RR enzyme

Methylene tetrahydrofolate

What is the role of methylene tetrahydrofolate in DNA synthesis?

It is a substrate for DNA synthesis

It acts as a methyl donor (correct)

It is a byproduct of DNA synthesis

It acts as a competitive inhibitor of thymidylate synthase

What is the purpose of the folate cycle?

To regenerate tetrahydrofolate Signup and view all the answers

What is the effect of 5-Fluorouracil on DNA synthesis?

It suppresses DNA synthesis Signup and view all the answers

Which of the following compounds is a byproduct of the conversion of dUMP to dTMP?

Dihydrofolate Signup and view all the answers

What is the role of thymidylate synthase in DNA synthesis?

It converts dUMP to dTMP Signup and view all the answers

Which of the following is NOT a nucleoside diphosphate used as a substrate for DNA synthesis?

UTP Signup and view all the answers

What is the role of dihydrofolate reductase in the folate cycle?

It regenerates tetrahydrofolate Signup and view all the answers

What is the purpose of DHFR in DNA synthesis?

To regenerate tetrahydrofolate Signup and view all the answers

What is the consequence of ADA deficiency?

Impaired DNA synthesis and cell proliferation Signup and view all the answers

What is the role of carbamoyl phosphate synthetase II (CPSII) in pyrimidine synthesis?

To convert CO2, glutamine, and aspartic acid to the pyrimidine ring Signup and view all the answers

What is the effect of elevated orotic acid levels in urine?

Deficiency in the pyrimidine synthesis pathway Signup and view all the answers

What is the purpose of ribonucleotide reductase in pyrimidine synthesis?

To convert UDP to dUDP Signup and view all the answers

What is the consequence of UTP inhibition on CPSII?

Inhibition of pyrimidine synthesis Signup and view all the answers

What is the consequence of ADA deficiency on immune cells?

Impaired immune response Signup and view all the answers

What is the purpose of xanthine oxidase inhibitors in treating ADA deficiency?

To reduce uric acid production Signup and view all the answers

What is the rate-limiting step in the de novo pyrimidine synthesis pathway?

CPSII-catalyzed reaction Signup and view all the answers

What is the consequence of orotic aciduria?

Retarded growth and anemia Signup and view all the answers

What is the purpose of uridine or cytidine treatment in orotic aciduria?

To supplement the missing products in the pathway Signup and view all the answers