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Physiology > Nucleotide Metabolism > Flashcards

Nucleotide Metabolism Flashcards

1
Q

What are the different molecules that Heterocyclic bases are found in?

A

Co-enzymes (E.g. NAD)

Energy Carriers (E.g. ATP)

Regulatory Enzymes (E.g. cAMP)

RNA and DNA precursors

Drug Analogues (drug having a structure similar to that of another compound)

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2
Q

What is the shape of a Heterocyclic Base? What is the significance of this?

A

It is flat (planar). This allows for “base stacking” in DNA.

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3
Q

What are the different kinds of purines

A

Adenine

Guanine

Hypoxanthine

Xanthine

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4
Q

What are the different kinds of Pyrimidines

A

Cytosine

Uracil

Thymine

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5
Q

What is the difference between the structure of Ribose and Deoxyribose?

A

Ribose: OH on 2’ C

Deoxyribose: H on 2’ C

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6
Q

What are the main examples of Intracellular Second Messengers

A

cAMP

cGMP

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7
Q

What are the three ways that Purines can be synthesised?

A
  1. De Novo Synthesis
  2. Phosphororibosylation of purines
  3. Phosphorylation of purine nucleosides
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8
Q

What is the precursor for purines

A

IMP

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9
Q

What comes from the Pentose-Phosphate pathway important in nucleotide synthesis

A

Ribose-5-phosphate

Thioredoxin

NADPH

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10
Q

Explain the conversion of IMP to GMP and AMP

A
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11
Q

What is the importance of PRPP

A

It provides the phosphoribose unit for nucleotide synthesis

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12
Q

What are the main reasons for tight regulation of nucleotide synthesis

A

Don’t want to waste energy and nitrogen

Waste products can accumulate

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13
Q

Explain the regulation of PRPP Synthase

A

Inhibited by:

  1. AMP and ADP
  2. GMP and GDP
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14
Q

Explain the regulation of PRPP Glutamyl Amidotransferase

A

Inhibited by:

  1. GMP
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15
Q

Explain the regulation of the conversion of IMP to AMPS

A

Inhibited by: AMP

Stimulated by: GTP

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16
Q

Explain the regulation of the conversion of IMP to XMP

A

Inhibited by: GMP

17
Q

Explain the regulation of the conversion of XMP to GMP

A

Stimulated by: ATP

18
Q

What are the consequences of folate deficiency

A

Sphinobifida

Megaloblastic anaemia

19
Q

What enables folate regeration

A

Vit B12

20
Q

Describe the salvage pathway for the creation of AMP

A
21
Q

Describe the salvage pathway for the creation of IMP

A
22
Q

Describe the salvage pathway for the creation of GMP

A
23
Q

In pyramidine synthesis, which step requires Folate? Explain this

A

Reaction 12 (not shown) requires H4 to be generated by dihydrofolate reductase

24
Q

Describe the conversion of oxyribonucleotides to deoxyribonucleotides

A
25
Q

Explain the salvage pathway for TMP

A
26
Q

What are the end-products of purine degradation

A

Purine ring left intact

Catabolised to uric acid

27
Q

What are the end-produces of pyrimidine degradation

A

Pyrimidine ring hydrolytically cleaved

Catabolised to CO2 and NH3

CO2 and NH3 are highly water soluable and easily excreted

28
Q

What is the normal urine uric acic concentration

A

0.24 mmol/L

29
Q

What is uric acid poorly soluable in?

A

Water

Synovial Fluid

Cold Temperatures

Metatarsophalangeal joints

30
Q

What are the “primary causes” of gout

A
  • High uric acid production
    • Due to enzyme abnormalities
  • Deficit in tubular transport
31
Q

What are the secondary causes of gout?

A
  • Low uric acid excretion
    • Thiazide Diuretics (reduce blood pressure)
  • High uric acid production due to cell breakdown
    • Severe infection
    • Cancer
32
Q

What are the treatments for gout

A
  • Colchicine and Anti-inflammatory drugs
    • Reduce acute arthritis
  • Probenecid
    • Enhance uric acid excretion in tubules
  • Allopurinol
    • Reduces uric acid in blood
  • Diet changes - less red meat and alcohol
    • Alcohol increases adenine nucleotide metabolism
33
Q

How does allopurinol work?

A

Xanthine oxidase competitive inhibitor.

Reduces uric acid in blood

34
Q

how does colchicine work?

A

Neutrophil phagocytosis inhibitor. Reduces acute arthritis

Physiology (3 decks)

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