Biosynthesis and Degradation of Nucleotides

Question 1

General structure of nucleotide

Answer 1

• Phosphate
• Purine or pyrimidine base
• Pentose

Question 2

Purines & Characteristics

Answer 2

• Adenine and Guanine
• Double ring
• Attaches 1-9

Question 3

Pyrimidines & Characteristics

Answer 3

• Cytosine, Thymine (DNA), Uracil (RNA)
• Single ring
• Attaches 1-1

Question 4

Two pathways of nucleotide biosynthesis

Answer 4

1. De novo pathway
2. Salvage pathway

Question 5

5 precursors of Purine Ring biosynthesis

Answer 5

• Aspartate
• CO2
• Glycine
• Formate
• Amide N of glutamine

Question 6

Synthesis of 5-Phosphoribosyl-1-pyrophosphate (PRPP)

Answer 6

Question 7

The first (rate limiting) reaction of purine biosynthesis

Answer 7

Question 8

Building of the purine ring starts on the ribonucleotide (step 2)

Answer 8

Question 9

Completion of five-membered ring after 5 steps

Answer 9

Question 10

The six membered ring is built on the five-membered ring

Answer 10

Question 11

______ is also a by-product of histidine biosynthesis.

Answer 11

AICAR

Question 12

Inosinate (IMP) is synthesized after 10 steps and is a precursor for _____ and ____.

Answer 12

AMP and GMP

Question 13

Biosynthesis of AMP

Answer 13

Question 14

Biosynthesis of GMP

Answer 14

Question 15

Regulation of AMP IMP biosynthesis

Answer 15

Question 16

Pyrimidine biosyntheis requires _____, _____, and ______.

Answer 16

• Aspartate
• PRPP
• Carbomoyl phosphate

Question 17

Carbamoyl phosphate is synthesized from ____ and ____ by ___________.

Answer 17

• CO2 and NH4+
• Carbamoyl phosphate synthetase II

Question 18

Pyrimidine biosynthesis

Answer 18

Question 19

_____ and ____ regulate the activity of aspartate transcarbamoylase.

Answer 19

ATP and CTP

Question 20

Reaction that converts nucleoside monophosphate to nucleoside diphosphate.

Answer 20

Question 21

Reaction that converts nucleoside monophosphate to nucleoside diphosphate and is specific for base but nonspecific for sugar.

Answer 21

Question 22

Reaction that converts nucleoside diphosphate to nucleoside triphosphate and is NOT specific for bases or sugar.

Answer 22

Question 23

Reduction of NDP to dNDP is carried out by _________.

Answer 23

Ribonucleotide Reductase

Question 24

At the primary regulatory sites, ribonucleotide reductase is activated by ______ and inhibited by _______.

Answer 24

• ATP
• dATP

Question 25

At the substrate specificity sites, ribonucleotide reductase is inhibited by _____ which CDP, UDP, and GDP are the substrates and _____ when UDP is the substrate, and activated by _____ which CDP and UDP are the substrates, _____ when GDP is the substrate, and _____ when ADP is the substrate.

Answer 25

- dGTP - dTTP - (d)ATP - dTTP - dGTP

Question 26

Source of dTMP synthesis

Answer 26

Question 27

Synthesis of dTMP

Answer 27

Question 28

Regeneration of THF

Answer 28

Question 29

Degradation of AMP

Answer 29

Question 30

Degradation of GMP

Answer 30

Question 31

High levels of uric acid causes \_\_\_\_.

Answer 31

Gout

Question 32

\_\_\_\_\_\_, an inhibitor of xanthine oxidase, helps in relieving gout related pain.

Answer 32

Allopurinol

Question 33

Action of Allopurinol in inhibition of uric acid formation

Answer 33

Question 34

Genetic defects in purine metabolism enzymes can cause serious problems. For example, ________ deficiency causes immunodeficiency diseases through poor development of T and B lymphocytes, which are crucial to the immune system.

Answer 34

Adenosine deaminase

Question 35

How adenosine deaminase deficiency works

Answer 35

1: Lack of adenosine deaminase leads to extremely high concentration of dATP 2: High dATP leads to general deficiency in the levels of all the dNTPs.

Question 36

Catabolism of Thymine

Answer 36

Question 37

Salvage pathway of Nucleotide biosynthesis using Adenine

Answer 37

Question 38

Salvage pathway of nucleotide biosynthesis using Hypoxanthine and Guanine

Answer 38

Question 39

Genetically-related lack of _____ causes _____ syndrome and serious problems. It affects children, mostly male, and after 2 years are found to be mentally retarded, badly coordinated, extremely hostile, and show compulsive self-mutilating tendencies.

Answer 39

- HGPRT - Lesch-Nyhan

Question 40

Lesch-Nyhan syndrome affects the brain, which depends heavily on \_\_\_\_\_\_\_\_. \_\_\_\_\_ levels are highest in the brain and ______ levels are low in brain.

Answer 40

- Salvage pathways - HGPRT - Glutamine-PRPP-amidotransferase

Question 41

Lesch-Nyhan syndrome patients have high levels of _____ due to ______ deficiency which causes ______ pain.

Answer 41

- Uric acid - HGPRT - Gout-related

Question 42

Allopurinol, an inhibitor of xanthine oxidase, helps in relieving gout-related pain. It however, does not help in alleviating the \_\_\_\_\_\_\_\_\_\_\_of the disease.

Answer 42

Neurological expressions

Question 43

Inhibitors of _______ are cancer treatment drugs since nucleotide biosynthesis requires nitrogen from glutamine at six different steps, facilitated by the action of this enzyme.

Answer 43

Glutamine amidotransferase

Question 44

Inhibitors of glutamine amidotransferase

Answer 44

- Glutamine - Azaserine - Acivicin

Question 45

Inhibitors of thymidylate synthase

Answer 45

Question 46

Inhibition mechanism of Thymidylate Synthase is an example of ______ or ______ based inhibition.

Answer 46

Suicidal or mechanism

Question 47

Inhibitors of dihydrofolate reductase

Answer 47