2. Nucleotides are organic molecules that serve as
the sub units of nucleic acid like DNA and RNA
Building blocks of nucleic acid.
Nucleotides are composed of a sugar molecule a
phosphate unit, and a nitrogenous base.
Nucleotides contain either a purine or
a pyrimidine base.
They are found everywhere within the cells of
our bodies, including the nucleus and the
cytoplasm.
3. Nucleotides are the activated precursors of DNA
and RNA.
ATP, an adenine nucleotide, is a universal
currency of energy in biological systems.
GTP is an essential carrier of chemical energy.
Components of the cofactors NAD+, FAD, and
coenzyme A
nucleotides function as cellular messengers for
communication from the outside to the inside of
the nucleus
They are activated intermediates in many
biosynthesis
4. Metabolism, inclusive term for the chemical
reactions by which the cells of an organism
transform energy, maintain their identity, and
reproduce.
Anabolism and Catabolism
Anabolism (synthesis) and catabolism
(destruction). Both processes go on
throughout the life of the organism.
5. Purines and pyrimidines are required
for synthesizing nucleotide
These molecules can be synthesized
either from denovo or salvaged from
existing bases
6. de novo pathway (a new):
nucleotides are synthesised from different
small components.
The synthesis of nucleotides begins with their
metabolic precursors: amino acids, ribose-5-
phosphate, CO2, and one-carbon units.
salvage pathways (to save from loss):
recovery and recycling of
nucleotides obtained in the diet
7. Basic pathway for biosynthesis of purine
nucleotides
occurs primarily in the liver
This pathway operates in cytoplasm.
Requires 10 steps overall
Purine ring is build up on a (R-5-P) as the
starting material step by step.
8. John Buchanan (1948) "traced" the sources of
all nine atoms of purine ring
N-1: aspartic acid
N-3, N-9: glutamine
C-4, C-5, N-7: glycine
C-6: CO2
C-2, C-8: one carbon units
21. shorter pathway than for purines
requires 6 steps (instead of 10 for purine)
Pyrimidine ring is made first, then attached to
ribose-P (unlike purine biosynthesis)
only 2 precursors (aspartate and glutamine,
plus HCO3
-) contribute to the 6-membered
ring
the product is UMP (uridine monophosphate)
23. •Carbamoyl phosphate synthetase(CPS) exists in 2 types:
•CPS-I, a mitochondrial enzyme, is dedicated to the urea cycle and
arginine biosynthesis.
•CPS-II, a cytosolic enzyme, used here. It is the committed step in animals.
29. Purines built up on ribose
PRPP synthetase: key step
First, synthesis IMP
Pyrimidine rings built, then ribose
added
CPS-II: key step
First, synthesis UMP
30. This pathway ensure the recovery and
recycling of nucleotides from existing
bases
This pathway is occure where the de
novo pathway is not operating;
importance in tissue like RBCs and
brain.
PRPP is the starting material in this
pathway.
31. During cellular metabolism and during
digestion in animals, nucleic acids are
degraded to mononucleotides,
nucleosides, and free purine bases.
The free purines are salvaged by 2 different
enzyme:
APRT (adenine phosphoribosyl transferase) for
adenine.
HGPRT (hypoxanthine guanine phosphoribosyl
transferase) for guanine or hypoxanthine.
33. Vasudevan DM,Sreekumari S
(2001).Textbook of biochemestry(for medical
students).JAYPEEBROTHERS medical
publishers LTD New Delhi.
Robert K Murray,Peter A Mayes, Daryle K
Granner,Victor W Rodwell(1990).Harper’s
biochemestry.Lange Medical publications
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