Nucleotide Metabolism Flashcards Preview

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Flashcards in Nucleotide Metabolism Deck (34):
1

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

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)

2

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

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

3

What are the different kinds of purines

Adenine

Guanine

Hypoxanthine

Xanthine

4

What are the different kinds of Pyrimidines

Cytosine

Uracil

Thymine

5

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

Ribose:  OH on 2' C

Deoxyribose: H on 2' C

6

What are the main examples of Intracellular Second Messengers

cAMP

cGMP

7

What are the three ways that Purines can be synthesised?

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

8

What is the precursor for purines

IMP

9

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

Ribose-5-phosphate

Thioredoxin

NADPH

10

Explain the conversion of IMP to GMP and AMP

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11

What is the importance of PRPP

It provides the phosphoribose unit for nucleotide synthesis

12

What are the main reasons for tight regulation of nucleotide synthesis

Don't want to waste energy and nitrogen

Waste products can accumulate

13

Explain the regulation of PRPP Synthase

Inhibited by:

  1. AMP and ADP
  2. GMP and GDP

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14

Explain the regulation of PRPP Glutamyl Amidotransferase

Inhibited by:

  1. GMP

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15

Explain the regulation of the conversion of IMP to AMPS

Inhibited by: AMP

Stimulated by: GTP

 

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16

Explain the regulation of the conversion of IMP to XMP

Inhibited by: GMP

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17

Explain the regulation of the conversion of XMP to GMP

Stimulated by: ATP

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18

What are the consequences of folate deficiency

Sphinobifida

Megaloblastic anaemia

19

What enables folate regeration

Vit B12

20

Describe the salvage pathway for the creation of AMP

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21

Describe the salvage pathway for the creation of IMP

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22

Describe the salvage pathway for the creation of GMP

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23

In pyramidine synthesis, which step requires Folate?  Explain this

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

24

Describe the conversion of oxyribonucleotides to deoxyribonucleotides

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25

Explain the salvage pathway for TMP

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26

What are the end-products of purine degradation

Purine ring left intact

Catabolised to uric acid

27

What are the end-produces of pyrimidine degradation

Pyrimidine ring hydrolytically cleaved

Catabolised to CO2 and NH3

CO2 and NH3 are highly water soluable and easily excreted

28

What is the normal urine uric acic concentration

0.24 mmol/L

29

What is uric acid poorly soluable in?

Water

Synovial Fluid

Cold Temperatures

Metatarsophalangeal joints

30

What are the "primary causes" of gout

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

31

What are the secondary causes of gout?

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

32

What are the treatments for gout

  • 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

How does allopurinol work?

Xanthine oxidase competitive inhibitor. 

Reduces uric acid in blood

34

how does colchicine work?

Neutrophil phagocytosis inhibitor.  Reduces acute arthritis