Biochemistry of Nucleic Acids Quiz

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary biological role of nucleic acids?

Energy storage

Structural support

Hormone production

Information storage and transfer (correct)

Which component is not a part of nucleotides?

Phosphate group

Amino acid (correct)

Sugar molecule

Nitrogenous base

What are the two main types of nucleic acids mentioned?

DNA and tRNA

mRNA and rRNA

DNA and RNA (correct)

DNA and mRNA

Which pathway is essential for the biosynthesis of purines?

De novo synthesis pathway Signup and view all the answers

What is the function of ribonucleotide reductase?

Converts ribonucleotides to deoxyribonucleotides Signup and view all the answers

Which sugar lacks a 2'-OH group?

2'-Deoxyribose Signup and view all the answers

What type of linkage is formed between a sugar and a nitrogenous base in a nucleoside?

N-glycosidic linkage Signup and view all the answers

At which carbon does a purine bond to a sugar?

C1' carbon Signup and view all the answers

How do nucleotides form?

By linking one or more phosphates with a nucleoside Signup and view all the answers

Which of the following correctly describes the numbering of sugars?

Numbering is primed Signup and view all the answers

What is the first step in the synthesis of Uridine Monophosphate (UMP)?

Transfer of a phosphate group Signup and view all the answers

Which enzyme catalyzes the attachment of the base to the ribose ring in UMP synthesis?

OPRT Signup and view all the answers

Which nitrogen sources are involved in the synthesis of the pyrimidine ring?

Aspartate and Glutamine Signup and view all the answers

What is unique about OMP decarboxylase in the pyrimidine pathway?

It does not form a high energy carbanion intermediate Signup and view all the answers

How many ATP molecules are needed in the first step of UMP synthesis?

Two ATPs Signup and view all the answers

What is the role of binding energy between OMP and the active site?

It stabilizes the transition state. Signup and view all the answers

Which enzyme catalyzes the transfer of phosphate to UMP to form UDP?

Nucleoside monophosphate kinase. Signup and view all the answers

In animals, which enzyme is primarily regulated for pyrimidine synthesis?

Carbamoyl phosphate synthetase II. Signup and view all the answers

What is a consequence of adenosine deaminase deficiency?

Severe combined immunodeficiency (SCID). Signup and view all the answers

How are deoxyribonucleotides formed from ribonucleotides?

Through reduction. Signup and view all the answers

What reaction is primarily regulated in bacteria for pyrimidine synthesis?

ATCase reaction. Signup and view all the answers

What happens to uracil when degraded in the liver?

It is converted to β-alanine. Signup and view all the answers

What general process occurs for the degradation of CMP and UMP?

Dephosphorylation, deamination, and glycosidic bond cleavage. Signup and view all the answers

What type of RNA is formed from ribonucleotides?

Ribonucleic acid Signup and view all the answers

Which of the following nucleotides contains Uracil?

Cytidine Monophosphate Signup and view all the answers

Which process uniquely involves ATP in purine nucleotide synthesis?

Group transfer Signup and view all the answers

What is the first purine derivative formed during de novo synthesis?

Inosine Mono-phosphate Signup and view all the answers

Which kind of nucleosides end in ‘-dine’?

Pyrimidine nucleosides Signup and view all the answers

What is the role of PRPP in nucleotide synthesis?

Precursor for pyrimidine synthesis Signup and view all the answers

Which molecule acts as a central regulator in purine nucleotide biosynthesis?

PRPP Signup and view all the answers

What impact does increasing concentrations of GTP have on AMP production?

Increases production Signup and view all the answers

Which component is NOT involved in purine ring synthesis?

C3: Propionate Signup and view all the answers

Which statement about IMP conversion is false?

GMP is derived from adenosine. Signup and view all the answers

What is the end product of all purine degradation?

Uric acid Signup and view all the answers

Which nucleotides are formed from IMP during purine metabolism?

AMP and GMP Signup and view all the answers

What is the role of hydrolyzing a phosphate from ATP during metabolic reactions?

It releases energy. Signup and view all the answers

What enzyme converts inosine to hypoxanthine during purine catabolism?

Purine nucleoside phosphorylase Signup and view all the answers

What is the final product of xanthine metabolism?

Uric acid Signup and view all the answers

Which enzyme catalyzes the conversion of adenosine to inosine?

Adenosine deaminase Signup and view all the answers

Which molecule is at the core of the purine degradation process?

Xanthine Signup and view all the answers

What is the role of xanthine oxidase in purine metabolism?

It catalyzes the conversion of xanthine to uric acid. Signup and view all the answers

Which alternate pathway can uric acid take after its formation?

Converted to urea. Signup and view all the answers

How do humans primarily excrete uric acid?

As insoluble crystals in urine. Signup and view all the answers

What substance is generated from aspartate at the expense of GTP in the purine nucleotide cycle?

Fumarate Signup and view all the answers

Which enzyme is responsible for recycling ribose sugar during xanthine degradation?

Ribose-1-phosphate isomerase Signup and view all the answers

Which enzyme is responsible for the irreversible conversion of adenine to AMP?

Adenine phosphoribosyl transferase (APRT) Signup and view all the answers

Study Notes

Nucleic Acids - Chemistry, Function & Metabolism

This lecture covers the structure, function, and associated disorders of nitrogenous bases, DNA, and RNA.
The structure of nitrogenous bases are planar, aromatic, and heterocyclic.
Bases are derived from purine or pyrimidine.
The numbering of bases is "unprimed."
The 5 carbon sugars are pentoses with numbering "primed."

Topic Outcomes

Describe the structure, function, and biological role of nucleosides, nucleotides, and their analogues.
Describe the structure, function, and types of nucleic acids (DNA, RNA).
Explain purine and pyrimidine biosynthetic pathways and their regulation.
Explain the role of ribonucleotide reductase.
Describe the disorders associated with purine and pyrimidine metabolism.

Nitrogenous Bases

Nitrogenous bases are categorized into purines (adenine, guanine) and pyrimidines (cytosine, thymine, uracil).
Thymine is a 5-methyl uracil.

Sugars

The 5-carbon sugars are known as pentoses.
Ribose and 2'-deoxyribose are important sugars.
The 2'-deoxyribose lacks a 2'-OH group.

Nucleosides

Formed by linking sugars with a purine or pyrimidine base through N-glycosidic linkage.
Purines bond to the C1' carbon of the sugar at their N9 atoms.
Pyrimidines bond to the C1' carbon of the sugar at their N1 atoms.

Nucleotides

Result from linking one or more phosphates to a nucleoside at the 5' end via esterification.
Phosphates can be bonded to either C3 or C5 atoms of the sugar.
Nucleotides can be mono-, di-, or triphosphates.

Nucleotides (Nucleic Acid Polymers)

Monomers for nucleic acid polymers.
Nucleoside Triphosphates are important energy carriers (ATP, GTP).
Important components of coenzymes (FAD, NAD+, and Coenzyme A).
RNA (ribonucleic acid) is a polymer of ribonucleotides.
DNA (deoxyribonucleic acid) is a polymer of deoxyribonucleotides.
Both deoxy- and ribonucleotides contain Adenine, Guanine, and Cytosine.
Ribonucleotides contain Uracil.
Deoxyribonucleotides contain Thymine.

Naming Conventions

Purine nucleosides end in "-sine" (e.g., adenosine, guanosine).
Pyrimidine nucleosides end in "-dine" (e.g., thymidine, cytidine, uridine).
Nucleotides are named by adding "mono-," "di-," or "triphosphate" to the nucleoside name.

Nucleotide Metabolism

Purine Ribonucleotides are formed de novo.
Purine synthesis starts with the formation of Inosine Monophosphate (IMP).
AMP and GMP are formed from IMP.
Purine ring components come from various amino acids and bicarbonate.

Purine Nucleotide Synthesis

ATP is involved in 6 steps of the synthesis process.
PRPP is a precursor for Pyrimidine, Histidine, and Tryptophan synthesis.
The C1 carbon notation changes from α to β in the second step.
Hydrolyzing a phosphate from ATP is relatively easy, with a ∆G°' of -30.5 kJ/mol.
The reaction is coupled to an exergonic reaction.
Parts of ATP can be transferred to an acceptor molecule (P₁, PP₁, adenyl, or adenosinyl).
ATP hydrolysis drives unfavorable reactions.

Purine Biosynthetic Pathway

Channeling reactions organize pathway to increase rate and protect intermediates from degradation.
Channeling is seen in reactions 3, 4, 6, 7, 8, and 10, 11 in animal cells.

IMP Conversion to AMP & GMP

IMP is converted to AMP and GMP via different pathways.

Regulatory Control of Purine Nucleotide Biosynthesis

GTP for AMP synthesis and ATP for GMP synthesis.
PRPP is a central molecule in purine synthesis.
ADP/GDP levels are important for negative feedback on Ribose Phosphate Pyrophosphokinase.
Amidophosphoribosyl transferase is activated by PRPP.

Purine Catabolism

Purine degradation leads to uric acid.
Ingested nucleic acids are degraded to nucleotides, then to nucleosides, by pancreatic/intestinal enzymes.
Nucleosides are absorbed directly and further degraded to various end products.
Intracellular purine catabolism starts with the break down of nucleotides into nucleosides by 5'-nucleotidase.
PNP (purine nucleoside phosphorylase) breaks down inosine into hypoxanthine.

Xanthine Degradation

Ribose is recycled from xanthosine into ribose 1-phosphate.
Hypoxanthine becomes xanthine via xanthine oxidase.
Guanine is converted to Xanthine via Guanine Deaminase.
Xanthine converts to uric acid via xanthine oxidase.

Xanthine Oxidase

A homodimeric protein with electron transfer proteins.
Contains FAD, Mo-pterin complex, and two 2Fe-2S clusters.
Transfers electrons to O2, forming toxic H₂O₂.
Toxic H₂O₂ is converted to water and O₂ by catalase.

The Purine Nucleotide Cycle

Combining reactions involves the deamination of aspartate to fumarate.

Uric Acid Excretion

Humans excrete uric acid into the urine as insoluble crystals.
Birds, reptiles, and some insects excrete uric acid in paste form.

Purine Salvage

Adenine phosphorybosyl transferase (APRT)
Hypoxanthine-Guanine phosphoribosyl transferase (HGPRT)
These are reversible reactions.

Gout

Impaired excretion or overproduction of uric acid.
Uric acid precipitates into joints, kidneys, and ureters, causing stones and gouty arthritis.
Lead poisoning inhibits uric acid excretion, linked to the Fall of the Roman Empire.
Xanthine oxidase inhibitors and allopurinol (a hypoxanthine analog) are used to treat gout.

Lesch-Nyhan Syndrome

A defect in the HGPRT enzyme.
Causes increased levels of hypoxanthine and guanine.
Results in impaired uric acid breakdown.
Neurological symptoms like spasticity, aggressiveness, and self-mutilation are also observed.

Purine Autism

25% of autistic patients may overproduce purines.
Urine tests over 24 hours are performed to diagnose in adolescence.

Pyrimidine Ribonucleotide Synthesis

Uridine Monophosphate (UMP) is synthesized first, then converted to CTP.
Pyrimidine ring synthesis is completed first, then attached to ribose-5-phosphate.
Aspartate, bicarbonate, and glutamine are sources for the pyrimidine ring.

Pyrimidine Synthesis

2 ATP required; one for transfer of phosphate.
Formation of carbamoyl aspartate and dihydroorotate.
Dihydroorotate dehydrogenase is an intra-mitochondrial enzyme.

UMP Synthesis Overview

2 ATPs needed (both used in the first step).
Carbamoyl aspartate and dihydroorotate are formed via condensation reactions.

OMP Decarboxylase

The final reaction in pyrimidine synthesis.
Catalysis is proficient.
High energy carbocation intermediate not required.

UTP and CTP Formation

Nucleoside monophosphate kinase transfers P to UMP to form UDP.
Nucleoside diphosphate kinase transfers P from ATP to UDP to form UTP.
CTP is formed from UTP via CTP Synthetase driven by ATP hydrolysis.
Glutamine provides amide nitrogen for C4.

Regulatory Control of Pyrimidine Synthesis

Bacteria utilize different regulation of ATCase.
Animals regulate carbamoyl phosphate synthetase II and activate it using ATP and PRPP.
UMP/CMP inhibits OMP decarboxylase competitively.
Purine synthesis is inhibited by ADP and GDP at the ribose phosphate pyrophosphokinase step, which regulates PRPP and pyrimidines.

Degradation of Pyrimidines

Involves dephosphorylation, deamination, and glycosidic bond cleavage to degrade CMP and UMP to bases.
Uracil is reduced in the liver into β-alanine.
Converted to malonyl-CoA for fatty acid synthesis.

Deoxyribonucleotide Formation

Purine/Pyrimidine Degradation pathways for ribonucleotides and deoxyribonucleotides are the same.

Adenosine Deaminase Deficiency

In purine degradation, adenosine is converted to inosine by ADA.
ADA deficiency causes SCID ("Severe Combined Immunodeficiency").
ADA deficiency selectively kills lymphocytes (B-cells and T-cells).
The active site is structurally perturbed in all known ADA mutants.

Adenosine Deaminase

Enzyme catalyzing deamination of Adenosine to Inosine.
α/β barrel domain structure; "TIM barrel" central structure.
Active site at bottom of funnel-shaped pocket formed by loops.
Found in glycolytic enzymes and proteins binding/transporting metabolites.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Test your knowledge on the fundamental roles and structures of nucleic acids. This quiz covers topics such as nucleotide components, biosynthesis pathways, and enzyme functions. Perfect for students studying biochemistry or molecular biology.