Test 2 - Nucleoside (Corrected)

Question 1

Nucleoside

Answer 1

Nitrogenous base + sugar

Question 2

Nucleotide

Answer 2

Phosphate added. to nitrogenous base and sugar

Question 3

Purines

Answer 3

Adenine and Guanine Built in steps onto PRPP

Question 4

Pyrimidines

Answer 4

Cytosine and Thymine Completed pyrimidine ring is added to PRPP

Question 5

Purine Synthesis First Commited Step?

Answer 5

• The donation of an amino group from Glutamine to PRPP. Adds amino group to C1, and removes phosphate group. (Highly unstable).
• Regulated by negative feedback of IMP, AMP, and GMP.
  
  • Allosteric inhibition by ADP and GDP.

Question 6

Difference between Synthase and a Synthatase?

Answer 6

• Synthatases: use ATP or GTP
  
  • Used in de novo synthesis.
• Synthase: do not

Question 7

What is the End Stage of De novo Purine Synthesis?

Answer 7

• Inosinate (IMP)
  
  • Hypoxanthine is the base on this molecue.
    
    • Last common step between AMP and GMP.
  • Can then be converted into AMP or GMP.
    
    • AMP and GMP inhibit their own synthesis.

Question 8

AMP and GMP synthesis

Answer 8

• They regulate one another. This prevents too much of one being made.
  
  • GTP is required to make AMP
  • ATP is required to make GMP.

Question 9

Broad Stroaks of de novo Purine synthesis.

Answer 9

1. Ribose 5-phosphate to PRPP
   
   1. Catalyzed by: PRPP synthetase
      
      1. Inhibited by ADP
2. PRPP to 5-phospho-ribosyl-amine
   
   1. Catalyzed by Glutamine giving amine group
      
      1. Inhibited by AMP, GMP, IMP
3. 5 - phosphoribosylamine to IMP
4. Divergence
   
   1. AMP production
      
      1. IMP to Adenylosuccinate
         
         1. Inhibited by AMP
      2. Adenylosuccinate to AMP
   2. GMP production
      
      1. IMP to XMP
         
         1. Inhibited by GMP
      2. XMP to GMP

Question 10

de novo Pyrimidine Biosynthesis First commited step?

Answer 10

• Is the combining of carbamoyl phosphate with aspartate.
  
  • Allosterically hindered by CTP.

Question 11

Unlike purine biosynthesis ______ is the precursor to the other pyrimidines?

and it is formed into what?

Answer 11

Uridylate (UMP)

Formed into a Triphosphate (UTP) prior to conversion.

Question 12

Feedback regulation of pyrimidine biosynthesis?

Answer 12

CTP inhibits synthesis

ATP + CTP results in almost normal activity but still less than normal rate.

Question 13

Where do the nucleoside monophosphates (NMP) get their phosphates?

Answer 13

• ATP donates
  
  • Catalyzed by each NMPs respective kinase
    
    • Eg. Adenylate kinase for AMP.
    • Sugar doesnt matter deoxy or ribo.

Question 14

Gout cause and treatment

Answer 14

• During purine degradation
  
  • AMP and GMP converted to Xanthine
  • Xanthine to Uric Acid
    
    • Catalyzed by Xanthine oxidase
      
      • Inhibited by Allopurinol
    • A build up of uric acid causes Gout

Question 15

Cause of Bubble people

Answer 15

• During Purine degradation
  
  • AMP to Adenosine
  • Adenosine to Inosine
    
    • Catalyzed by Adenosine Deaminase (ADA)
      
      • A deficiency in ADA results in 100 fold increase in dATP which results in defects in T and B lymphocyte development.

Question 16

End product of Purine metabolism in humans?

Answer 16

Uric acid

Question 17

End product of Pyrimidine degradation?

Answer 17

Urea

Question 18

What causes Lesch-Nyhan Syndrome?

Answer 18

• Defect in the salvage process of Hypoxanthine or Guanine
  
  • This is due to a coding defect in the enzyme HGPRT.
    
    • X-Linked
    • ​Purine overproduction
    • Gout and Kidney stones
    • Neurological problems
    • Mental retardation
    • Bizzare self mutilation.

Question 19

What is this?

Answer 19

Adenine

Question 20

What is this?

Answer 20

Guanine

Question 21

What is this?

Answer 21

Cytosine

Question 22

What is this?

Answer 22

Thymine

Question 23

What is this?

Answer 23

Uracil