BIOCHEM NUCLEOTIDES

Question 1

are building blocks of
nucleic acids (DNA & RNA) and are
essential for several biological functions

Answer 1

Nucleotides

Question 2

metabolic functions of Nucleotides

Answer 2

• Energy metabolism (ATP)
• Protein synthesis
• Regulation of enzyme activity
• Signal transduction (cAMP, cGMP)

Question 3

also form
parts of coenzymes
and are intermediates
in metabolic pathways
such as sugar and lipid
synthesis.

Answer 3

Nucleotides

Question 4

Structural Components of Nucleotides

Answer 4

Nitrogenous base, Pentose sugar, * Phosphate group

Question 5

• Ribose (RNA)
• Deoxyribose (DNA)

Answer 5

Pentose sugar

Question 6

• Purines: Adenine (A), Guanine (G)
• Pyrimidines: Cytosine (C), Thymine (T), Uracil (U)

Answer 6

Nitrogenous base

Question 7

Double-ring
structure (e.g., Adenine,
Guanine)

Answer 7

Purines

Question 8

Single-ring
structure (e.g., Cytosine,
Thymine, Uracil).

Answer 8

Pyrimidines

Question 9

Purines and pyrimidines
exist primarily in ____ and
_________ tautomeric forms,
crucial for the integrity of
base pairing.

Answer 9

oxo, amino

Question 10

Nucleosides are named
based on the ____________________

Answer 10

nitrogenous base

Question 11

Nucleosides Consist of a ______
attached to a _______________ via an ______________________

Answer 11

base (purine/pyrimidine), sugar (ribose
or deoxyribose), N- glycosidic bond.

Question 12

are named based
on the nucleoside and the
number of phosphate groups

Answer 12

Nucleotides

Question 13

Nucleosides phosphorylated
at the _________ position of the
sugar, forming structures

Answer 13

3’ or 5’

Question 14

a critical
nucleotide, consists of
adenine, ribose, and
three phosphate
groups

Answer 14

ATP

Question 15

predominant form under physiological conditions

Answer 15

Anti Conformations

Question 16

Nucleotides exhibit restricted rotation
around the glycosidic bond due to steric
hindrance, existing as ____ and ______
conformers,

Answer 16

syn, anti

Question 17

Nucleotides are linked by ________ phosphodiester
bonds forming the backbone of DNA/RNA.

Answer 17

3’→5’

Question 18

5’ and 3’ ends give the molecules _________, and
sequences are _______ from 5’ to 3’

Answer 18

direction, written

Question 19

*DNA is more stable than RNA due to
the absence of a _______________ group,
reducing its susceptibility to hydrolysis

Answer 19

2’ hydroxyl

Question 20

RNA and DNA modifications are important in
____________________ and __________________.

Answer 20

gene regulation, mRNA stability

Question 21

is the main energy
currency in cells,

Answer 21

ATP

Question 22

is crucial in protein
synthesis and signal transduction

Answer 22

GTP

Question 23

ATP’s high energy comes from its two anhydride bonds, with hydrolysis releasing around ________

Answer 23

-30 kJ/mol

Question 24

Serve as second messengers in cellular signaling pathways.

Answer 24

cAMP and cGMP

Question 25

mediates hormonal responses,

Answer 25

cAMP

Question 26

is involved in processes like smooth muscle relaxation

Answer 26

cGMP

Question 27

ATP is __________ (~1 mmol/L), while cAMP is much _________ (~1 nmol/L), reflecting their distinct roles.

Answer 27

abundant, lower

Question 28

Many coenzymes, such as NAD, FAD, and Coenzyme A, contain _____________________, enabling them to participate in redox reactions and metabolic pathways.

Answer 28

nucleotides (AMP)

Question 29

Acts as a methyl donor in numerous biochemical reactions, essential for methylation processes.

Answer 29

S-Adenosylmethionine

Question 30

Anticancer Agents example

Answer 30

5-fluorouracil, 6- thioguanine

Question 31

Synthetic analogs like 5-fluorouracil and 6- thioguanine disrupt ______ synthesis or function by inhibiting _________ or incorporating into nucleic acids.

Answer 31

DNA, enzymes

Question 32

These drugs are used to treat cancer, suppress immune responses in organ transplants, or treat viral infections (e.g., AZT for HIV)

Answer 32

Anticancer Agents

Question 33

__________________________ of nucleoside triphosphates help distinguish the effects of nucleotide binding from phosphoryl transfer, valuable in studying enzyme mechanisms.

Answer 33

Non-hydrolyzable analogs

Question 34

are synthesized de novo from amphibolic intermediates in human tissues, making them dietarily nonessential

Answer 34

Purines and Pyrimidines

Question 35

Humans synthesize purines de novo, mainly starting from _______________ and ______, producing ________________________ through a series of regulated steps

Answer 35

ribose-5-phosphate, ATP, inosine monophosphate (IMP)

Question 36

IMP produces

Answer 36

AMP and GMP

Question 37

Phosphoryl transfer from ATP = ______ → _______

Answer 37

GDP, GTP

Question 38

Oxidative phosphorylation = ADP → _____

Answer 38

ATP

Question 39

PRPP (Phosphoribosyl pyrophosphate) is crucial, and its synthesis is regulated by ______________________ by AMP, ADP, GMP, and GDP

Answer 39

feedback inhibition

Question 40

Anticancer drugs, like methotrexate and 6- mercaptopurine, inhibit steps in purine biosynthesis by blocking _________ or ________________

Answer 40

folate, glutamine analogs

Question 41

Purines can also be recycled through salvage pathways, converting bases to ___________ using _________

Answer 41

nucleotides, PRPP

Question 42

Phosphorylation of purine nucleotides is catalyzed by ______________

Answer 42

adenosine kinase

Question 43

Pyrimidines, like ______________________ are also synthesized de novo.

Answer 43

uracil and cytosine,

Question 44

Unlike purines, PRPP is used only after the _________________ is synthesized

Answer 44

pyrimidine ring

Question 45

The enzyme __________UTP controls early pyrimidine biosynthesis.

Answer 45

CAD

Question 46

CAD is regulated at both transcriptional and enzymatic levels, activated by ______ and inhibited by _______

Answer 46

PRPP, UTP

Question 47

Pyrimidines are also recycled, but their catabolites are ______________________, making overproduction clinically insignificant.

Answer 47

highly water-soluble

Question 48

Purines are catabolized to _______.

Answer 48

uric acid

Question 49

Disorders in purine catabolism, like ______ (due to excess uric acid), result in inflammatory conditions

Answer 49

gout

Question 50

deposition of urate crystals occur in _______ and _______

Answer 50

tissues, joints

Question 51

defect in the HGPRT (hypoxanthine-guanine phosphoribosyl transferase) enzyme

Answer 51

Lesch-Nyhan syndrome

Question 52

* deficiencies in enzymes of pyrimidine biosynthesis * megaloblastic anemia and developmental delays

Answer 52

Orotic aciduria

Question 53

* severe immunodeficiency caused by

Answer 53

Adenosine deaminase deficiency

Question 54

* Impairs T-cell function caused by

Answer 54

purine nucleoside phosphorylase deficiency

Question 55

Pyrimidine catabolism produces ________, _____, and __________, which are water-soluble and excreted without issues

Answer 55

β-alanine,CO2, ammonia

Question 56

Disorders such as ____________________ arise from deficiencies in dihydropyrimidine dehydrogenase, leading to neurological complications

Answer 56

β-hydroxybutyric aciduria

Question 57

Coordinated regulation between _______ and _____________ metabolism ensures balance for nucleic acid biosynthesis

Answer 57

purine, pyrimidine

Question 58

Anticancer drugs (e.g., 5-fluorouracil, methotrexate) exploit the______________ of purine synthesis, slowing cell division

Answer 58

folate dependence