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Questions and Answers
What are the three constituent parts that DNA and RNA break down into?
What are the three constituent parts that DNA and RNA break down into?
Which nitrogenous bases are classified as purines?
Which nitrogenous bases are classified as purines?
What is the suffix used for naming purine bases?
What is the suffix used for naming purine bases?
What type of linkage connects nucleotides in nucleic acids?
What type of linkage connects nucleotides in nucleic acids?
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What is the primary source for nucleotides utilization in metabolism?
What is the primary source for nucleotides utilization in metabolism?
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Which pathway begins with metabolic precursors like amino acids and ribose 5-phosphate?
Which pathway begins with metabolic precursors like amino acids and ribose 5-phosphate?
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Which component is not part of a nucleotide?
Which component is not part of a nucleotide?
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What does the salvage pathway primarily recycle?
What does the salvage pathway primarily recycle?
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What accounts for 90% of daily purine nucleotide biosynthesis?
What accounts for 90% of daily purine nucleotide biosynthesis?
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Which enzyme is primarily responsible for the recycling of hypoxanthine and guanine?
Which enzyme is primarily responsible for the recycling of hypoxanthine and guanine?
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In which tissues does the salvage pathway primarily occur?
In which tissues does the salvage pathway primarily occur?
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Which reaction is catalyzed by adenosine phosphoribosyltransferase (APRT)?
Which reaction is catalyzed by adenosine phosphoribosyltransferase (APRT)?
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What is the primary advantage of the salvage pathway over the de novo pathway?
What is the primary advantage of the salvage pathway over the de novo pathway?
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What happens if purines are not salvaged?
What happens if purines are not salvaged?
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Which of the following statements about PRPP is true?
Which of the following statements about PRPP is true?
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Which of the following nucleotides is NOT directly produced by salvaging pathways?
Which of the following nucleotides is NOT directly produced by salvaging pathways?
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Which molecule is synthesized first in nucleotide metabolism?
Which molecule is synthesized first in nucleotide metabolism?
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What is the primary product of purine de novo synthesis?
What is the primary product of purine de novo synthesis?
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Which enzyme catalyzes the conversion of ribose-5-phosphate to PRPP?
Which enzyme catalyzes the conversion of ribose-5-phosphate to PRPP?
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How many moles of ATP are required to synthesize Inosine Monophosphate (IMP)?
How many moles of ATP are required to synthesize Inosine Monophosphate (IMP)?
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What is the role of GTP in purine metabolism?
What is the role of GTP in purine metabolism?
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What is generated by the action of PRPP synthetase?
What is generated by the action of PRPP synthetase?
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During purine synthesis, what is the significance of the branch point at IMP?
During purine synthesis, what is the significance of the branch point at IMP?
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What effect does an accumulation of excess GTP have on AMP and GMP synthesis?
What effect does an accumulation of excess GTP have on AMP and GMP synthesis?
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What is the final product of purine nucleotide catabolism?
What is the final product of purine nucleotide catabolism?
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Which step is the first in the degradation of adenosine?
Which step is the first in the degradation of adenosine?
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A deficiency in which enzyme leads to Severe Combined Immunodeficiency (SCID)?
A deficiency in which enzyme leads to Severe Combined Immunodeficiency (SCID)?
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Which of the following is associated with gout?
Which of the following is associated with gout?
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What is the first step in guanosine degradation?
What is the first step in guanosine degradation?
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Which condition is characterized by a lack of the HGPRT enzyme?
Which condition is characterized by a lack of the HGPRT enzyme?
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The accumulation of uric acid can lead to which of the following conditions?
The accumulation of uric acid can lead to which of the following conditions?
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Which enzyme is critical for purine salvage in rapidly dividing cells?
Which enzyme is critical for purine salvage in rapidly dividing cells?
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Which enzyme is primarily responsible for the conversion of ribonucleotides to deoxyribonucleotides?
Which enzyme is primarily responsible for the conversion of ribonucleotides to deoxyribonucleotides?
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What is the initial substrate for the synthesis of deoxythymidine nucleotides?
What is the initial substrate for the synthesis of deoxythymidine nucleotides?
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Which statement about thymidine nucleotides is correct?
Which statement about thymidine nucleotides is correct?
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Which of the following is NOT a part of a deoxyribonucleotide?
Which of the following is NOT a part of a deoxyribonucleotide?
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Which of the following sequences accurately describes the synthesis pathway from UMP to dTMP?
Which of the following sequences accurately describes the synthesis pathway from UMP to dTMP?
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What is the role of dATP in the regulation of ribonucleotide reductase?
What is the role of dATP in the regulation of ribonucleotide reductase?
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How does binding of dTTP to the specificity site of ribonucleotide reductase affect nucleotide synthesis?
How does binding of dTTP to the specificity site of ribonucleotide reductase affect nucleotide synthesis?
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What condition describes an elevated serum uric acid concentration?
What condition describes an elevated serum uric acid concentration?
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In humans, what is the typical normal concentration range of uric acid in serum?
In humans, what is the typical normal concentration range of uric acid in serum?
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Which enzyme's lack of feedback control can lead to elevated purine synthesis?
Which enzyme's lack of feedback control can lead to elevated purine synthesis?
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What metabolic disorder is associated with the overproduction of uric acid?
What metabolic disorder is associated with the overproduction of uric acid?
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What happens during severe hyperuricemia with respect to sodium urate?
What happens during severe hyperuricemia with respect to sodium urate?
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Which syndrome results from the deficiency of the HGPRT enzyme?
Which syndrome results from the deficiency of the HGPRT enzyme?
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Study Notes
Nucleic Acid Metabolism
- Nucleic acids are polymers of nucleotides
- Nucleotides are the fundamental building blocks of nucleic acids
- Nucleotides consist of a sugar molecule (either ribose or deoxyribose), a phosphate group, and a nitrogen-containing base
- The nitrogenous base is either a purine or a pyrimidine
- RNA and DNA are polymers made of long chains of nucleotides
- RNA contains ribose, while DNA contains deoxyribose
- DNA contains the bases Adenine (A), Guanine (G), Cytosine (C), and Thymine (T). RNA contains Uracil (U) instead of thymine
Learning Objectives
- Students should be able to describe how nucleotides are synthesized in cells
- Distinguish between the two pathways for nucleotide biosynthesis: de novo and salvage pathways
- Describe the de novo and salvage synthesis of purines
- Understand the synthesis of IMP (precursor of adenine and guanine)
- Describe the synthesis of adenine and guanine from IMP
- Describe the de novo and salvage synthesis of pyrimidines
- Understand the synthesis of uracil, cytosine, and thymine
- Understand the degradative processes of purines and pyrimidines
- Explain the synthesis of deoxyribonucleotides from ribonucleotides
Functions of Nucleotides in Cells
- Precursors of DNA and RNA
- Chemical Energy Carriers (ATP, GTP)
- Components of co-factors (NAD+, FAD, Co-enzyme A)
- Components of activated biosynthetic intermediates (UDP-glucose)
- Cellular secondary messengers (cAMP, cGMP)
Nucleic Acids Metabolism
- Our bodies metabolize DNA and RNA breaking them down into their constituent parts: phosphate, pentose sugar, and nitrogenous bases
- DNA contains thymine, RNA contains uracil
Nucleotide Formation
- The base is added at the 1' position and phosphate groups are added at the 5' position
De Novo Synthesis of Purines
- Primarily occurs in the liver
- Begins with PRPP and leads to the formation of inosine 5'-monophosphate (IMP), the first fully formed nucleotide
Step 1: PRPP Production
- PRPP synthetase and ATP convert ribose-5-phosphate to phosphoribosyl-1-pyrophosphate (PRPP)
- The reaction releases AMP and consumes two high-energy phosphate bonds
Step 2: Synthesis of Inosine Monophosphate (IMP)
- The rate-limiting step in the synthesis is catalyzed by glutamine-PRPP amidotransferase
- Five moles of ATP, two moles of glutamine, one mole of glycine, one mole of CO2, one mole of aspartate, and two moles of formate are required to form IMP
Degradation of Purine Nucleotides
- The process generates uric acid, which is an insoluble compound and is excreted in the urine.
De Novo Synthesis of Pyrimidines
- Pyrimidine nucleotides are synthesized in a stepwise manner, beginning with the formation of carbamoyl phosphate and culminating in the creation of UMP.
Pyrimidine Degradation and Salvaging Reactions
- Various enzymes catalyze reactions that involve the breakdown of cytosine, uracil, and thymine
- Salvaging reactions recycle these pyrimidine bases.
Deoxyribonucleotide Synthesis
- Deoxyribonucleotides are derived from the corresponding ribonucleotides by direct reduction of the ribose sugar at carbon 2 (deoxypurines/deoxypyrimidines are formed).
- Ribonucleotide reductase catalyzes this reduction, yielding dADP, dGDP, dCDP, and dUDP.
- dTTP is created from dUTP after dUTP is created by reduction of UTP.
Regulation of dNTP Synthesis
- The overall activity of ribonucleotide reductase must be tightly controlled.
- ATP activation and dATP inhibition can influence enzyme activity.
Disorders of Nucleotide Metabolism
- Several inherited genetic disorders can affect nucleotide metabolism. These lead to a multitude of symptoms depending on the impacted enzyme.
Drugs that Affect Nucleotide Biosynthesis
- These drugs are often used in cancer treatment by inhibiting the enzymes related to the synthesis and replication of RNA or DNA.
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Description
Test your knowledge on the fundamental aspects of DNA and RNA, focusing on their constituent parts and the biochemical pathways involved in nucleotide metabolism. This quiz covers concepts such as purines, the salvage pathway, and enzymatic recycling processes.
