The Many Fates of Nitrogen: Part 2

This set of flashcards covers key concepts, terms, and processes related to nucleotide metabolism, purine and pyrimidine synthesis, and associated disorders, preparing students for upcoming exams.

What are the two types of nucleotides compared in metabolism?

Purines and Pyrimidines.

What syndrome is characterized by the deficiency of HGPRT?

Lesch-Nyhan syndrome.

What is the role of cyclic AMP in cellular processes?

It acts as a secondary messenger in signaling pathways.

What is PRPP?

5-Phosphoribosyl-1-pyrophosphate, a key intermediate in nucleotide synthesis.

Which vitamins are mentioned as playing roles in biochemical reactions?

Vitamin B6 (PLP), Vitamin B9 (THF), and others.

What does ADA stand for in nucleotide metabolism context?

Adenosine Deaminase.

What condition arises from a deficiency in ADA?

Severe Combined Immunodeficiency (SCID).

What is the end product of purine metabolism?

Uric Acid.

What is the primary function of ribonucleotide reductase?

To convert ribonucleotides into deoxyribonucleotides.

What similarities do purine bases have in DNA and RNA?

Adenine (A) pairs with Thymine (T) in DNA and Uracil (U) in RNA, while Guanine (G) pairs with Cytosine (C) in both.

What is the significance of salvage pathways in purine metabolism?

They recycle nucleotides to prevent wastage.

Which molecule activates PRPP amidotransferase (PPAT)?

PRPP activates PPAT.

Name one drug that inhibits purine synthesis and is used in cancer treatment.

Methotrexate.

What metabolic disorder does hyperuricemia lead to?

Gout.

Describe the role of FAD in metabolic reactions.

FAD functions as a redox cofactor, accepting and donating electrons.

What does UMP synthase do?

Catalyzes the last two steps of pyrimidine synthesis.

Which two pathways are associated with the pentose phosphate pathway?

Oxidative and Non-oxidative pathways.

What is the key result of purine degradation?

Formation of uric acid.

What characterizes the structure of purines?

Purines consist of a two-ring nitrogenous base.

What type of nucleotide is Adenine (A)?

A purine.

What is the first pyrimidine base synthesized?

Orotate.

What role does Adenylosuccinate synthetase play in metabolism?

It catalyzes the conversion of IMP to AMP.

What are the two end products of de novo purine synthesis?

AMP and GMP.

What is the physiological role of vitamins in nucleotide metabolism?

They serve as coenzymes in the synthesis and degradation of nucleotides.

What is the significance of the 5' and 3' ends of nucleotides?

They determine the directionality of DNA and RNA strands.

How are nucleotides involved in energy transfer within the cell?

They store and transfer energy through high-energy phosphate bonds.

What regulatory role does PRPP play in nucleotide metabolism?

PRPP activates several key enzymes in nucleotide biosynthesis.

Which nitrogenous base pairs with Cytosine (C) in both DNA and RNA?

Guanine (G).

Which enzyme is responsible for converting UTP to CTP?

CTP synthetase.

How many nitrogens do Gly, Asp, and Gln donate during IMP synthesis?

Three nitrogens.

What is the common mechanism for thymidine synthesis?

Methylation of dUMP to dTMP.

What forms the basis of the nucleotide salvage pathway?

The recycling of free bases and nucleosides into nucleotide pools.

What is a key defining feature of pyrimidines?

Pyrimidines consist of a single-ring nitrogenous base.

What compound must be regenerated for nucleotide synthesis to proceed efficiently?

N5, N10-methylene-tetrahydrofolate (THF).

What does CAD stand for in pyrimidine biosynthesis?

Carbamoyl phosphate synthetase II, Aspartate transcarbamylase, Dihydroorotase.

Which two types of nucleotides are both essential for DNA and RNA structure?

Ribonucleotides and Deoxyribonucleotides.

What is thymidylate synthase's main role?

To convert dUMP to dTMP by adding a methyl group.

Which enzyme is inhibited by both methotrexate and 5-fluoro-uracil?

Thymidylate synthase.

What does the salvage pathway specifically recycle?

Purines and pyrimidines from nucleic acid turnover.

What is a key consequence of Lesch-Nyhan syndrome?

Developmental and behavioral pathologies, including self-mutilation.

What is the first reaction in the heme synthesis pathway?

The formation of d-aminolevulinic acid (ALA) from glycine and succinyl CoA.

What compound provides the first nitrogen in heme synthesis?

Glycine.

What is the principle of gene therapy for SCID?

To correct the underlying enzyme deficiency in patients.

What does CPS stand for in nucleotide metabolism?

Carbamoyl Phosphate Synthetase.

Which molecule is a cofactor for ALA synthase?

Pyridoxal Phosphate (PLP).

What is the function of the purinosome?

To organize purine synthesis enzymes and metabolites.

What is the link between folate and nucleic acid metabolism?

Folate is crucial for the synthesis of nucleotides, some through the formyl-THF pathway.

Which process in purine metabolism can result in gout?

Excessive degradation leading to hyperuricemia.

What is the function of Thymidylate synthase in cancer therapy?

Its inhibition leads to reduced DNA synthesis in rapidly dividing cells.

What are the two main symptoms of frank hemolytic anemia?

Severe jaundice and anemia.

How is reduced blood flow related to clot formation?

Poor blood flow can lead to conditions for thrombosis, contributing to clots.

What does X-linked hemophilia stem from?

Deficiency in factors VIII or IX.

What is the outcome of cleaving fibrinogen by thrombin?

The formation of a soft clot from fibrinogen.

What role do anticoagulants play in thrombotic conditions?

They inhibit excessive clot formation.

How is the intrinsic pathway triggered in the coagulation cascade?

By the exposure of blood to collagen or negatively charged surfaces.

In thrombotic therapy, what role does tPA serve?

It activates plasminogen to plasmin, helping dissolve clots.

What type of protein are zymogens?

Inactive precursor enzymes.

How does vitamin K contribute to coagulation?

It is essential for the synthesis of Gla residues in clotting factors.

What distinguishes primary from secondary hemostasis?

Primary involves platelet plug formation; secondary involves fibrin mesh stabilization.

What type of feedback mechanism do purine and pyrimidine pathways utilize?

Feedback inhibition.

How do pyrimidines differ structurally from purines?

Pyrimidines have a single ring structure, while purines have a double ring.

What is the function of HEXO in the pentose phosphate pathway?

Hexose-6-phosphate dehydrogenase catalyzes an early step in the pathway.

What role do natural inhibitors like sulfonamides play in bacterial metabolism?

They inhibit folate synthesis, disrupting bacterial nucleotide synthesis.

What is uridine's relationship to RNA?

It is a base found in RNA, pairing with adenine (A).

Why is vitamin B12 significant for nucleotide metabolism?

It is crucial for DNA synthesis and red blood cell formation.

What is the clinical relevance of left-shifting enzyme assays in diagnosing heme pathologies?

It allows for the detection of deficiencies in the heme synthesis pathway.

What are the clinical implications of elevated uric acid levels?

They can lead to gout and kidney stones.

Describe the productive use of ribose-5-phosphate in organisms.

It provides a sugar backbone for nucleic acids and nucleotides.

What is homocystinuria's biochemical mechanism?

It results from defects in homocysteine metabolism, part of amino acid processing.

What is the significance of the urea cycle in nitrogen metabolism?

It detoxifies ammonia by converting it to urea for excretion.

What occurs during the negative feedback loop in nucleotide synthesis?

End products inhibit their own synthesis pathway to prevent overproduction.

How are amino acids connected to nucleotide metabolism?

They donate nitrogen atoms during nucleotide synthesis.

How many different purine bases are generally found in nucleic acids?

Two: adenine and guanine.

What do you understand by purine salvage?

It is a mechanism to recover purine bases and nucleosides from degradation.

What is the significance of carbamoyl phosphate?

It is a building block for the synthesis of pyrimidines.

How does heme synthesis relate to iron levels in the body?

Iron is a crucial component of heme and influences its production.

What consequence can lead poisoning have on heme synthesis?

It can cause acquired porphyrias by blocking key steps in the pathway.”},{