How Nucleic Acids Go
From Here To There
By: Laura Capparilli, Tyler Horton, Zach Johnston, and Kim Hagey
S
DNA
S Characteristics of DNA: double-stranded, double helix,
antiparallel
S Nucleic Acid: polymeric macromolecules made from nucleotide
monomers
S Nucleotide: An organic molecule that serves as a monomer of
nucleic acid
S Nucleoside: any various compound of sugar paired with either a
purine or pyrimidine
RNA
S Characteristics:
single-stranded
S Uracil replaces Thymine
S
Bases: Purines and Pyrimidines
S
Purine: A nitrogen-containing
substance derived from uric acid
S
S
S
S
Base Paring in DNA: A=T, C=G
Purine bases: Adenine and Guanine
S
Base Pairing in RNA: A=U, C=G
Pyrimidine: A nitrogenous base with a
six-sided structure
S
Main functions:
Pyrimidine bases: Cytosine, Thymine,
Uracil
S
1. DNA/RNA Replication
S
Short Term energy storage of ATP
Breakdown
in GI
Mouth – Mastication &
Deglutition
Esophagus- movement of
bolus via peristalsis through
LES
Stomach- Nucleic
Acids dissolve in gastric
chyme
Digestion in the Small Intestine
Chyme enters the
duodenum, and the
pancreas releases
pancreatic juice
which contain:
Ribonuclease - breaks
down RNA into
ribonucleotides
Deoxyribonuclease breaks down DNA into
deoxyribonucleotides
Digestion in the Small Intestine
BrushBorder
Further digestion
occurs at the
microvilli in the S.I.
from two enzymes:
Phosphatases
&
Nucleosidases
Products of Digestion
S So your final products are Phosphate ion, pentose sugars,
and a nitrogenous base.
S Duodenum and Jejunum absorb the products in the
epithelial cells.
Absorption
S Membrane transport proteins carry the products to the
simple columnar using active and secondary transport.
Absorption
S Diffusion of the products from the simple columnar
epithelium across the basolateral membrane into the
interstitial fluid, into the capillary.
S Where the Pyrimidines and Purine bases undergo De-Novo
Synthesis, the pathway, and Salvage Pathway
De-novo Synthesis
S Why? Nucleic acids may not be readily available
S De-novo synthesis is the creation of complex molecules
from simpler molecules like sugars or amino acids
S De-novo synthesis also refers to the process of DNA
replication
S For example, primase is an RNA polymerase and it can add
a primer to an existing strand. DNA polymerase cannot and
therefore needs to add the primer, de-novo
S The de-novo pathway does not use free bases (A,G,C,T,U)
De-novo Pathway
S The purine ring is built up one atom or a few atoms at a
time and attached to ribose throughout the process
S The pyrimidine ring is synthesized as orotate (heterocyclic
compound) and attached to ribose phosphate
S The ribose phosphate is converted into common pyrimidine
nucleotides
S The enzymes involved in De-novo synthesis are present as
large multienzyme complexes, such as folate, carbon
dioxide, and glutamine.
Salvage Pathway
S Bases and nucleosides are formed during
degradations of RNA & DNA
S The SALVAGE PATHWAY is used to recover
these molecules
S This is especially important in tissues that
cannot undergo De Novo Synthesis
Salvage Pathway
Human Urate Homeostasis
S Urate is produced as the major end product of purine metabolism
by liver, muscles, and intestine.
S The biosynthesis of urate is catalyzed by xanthine oxidase (XO).
S Approximately two thirds of the daily turnover of urate is
accounted for by urinary excretion, with the remaining one third
being excreted into the gut as feces.
Purine Degredation
Guanine and Adenine are converted to Uric Acid
Products of pathway
S Nuclease frees the nucleotide
S Nucleotidase frees guanosine
S Guanosine is converted to guanine
S Guanine converted to xanthine
S Xanthine converted to uric acid
Hyperuricemia
S An abnormally high level of uric acid in the blood.
S High levels of uric acid in the blood can lead to gout, which
is a medical condition characterized by recurrent attacks of
acute inflammatory arthritis.
Gout
Valsalva Maneuver
S Forceful attempted expulsion of air with plugged nose and
closed mouth
S Clears pressure in the middle ear
Valsalva Maneuver
S 4 stages:
1.
Initial Pressure Rise
2.
Reduced Venous Return and Compensation
3.
Pressure Release
4.
Return of Cardiac Output
Valsalva Maneuver
Valsalva Maneuver
S Can help diagnose:
S Cardiovascular issues
S Neurological issues
S Urogenital Problems
Valsalva Maneuver
S Clinically, the Valsalva Maneuver is done against a closed
glottis
S This is a common sensation when exerting force such as
lifting a heavy object or trying to force defecation
Defecation Reflex
S Defecation is the final act of digestion by which organisms
eliminate solid, semisolid, or liquid waste from the GI tract
via the anus
Defecation Reflex
S The rectum ampulla (dilated section of the rectum where
feces is stored until it is expelled) acts as a temporary fecal
reservoir
S As rectal walls stretch due to filling, stretch receptors
stimulate the desire to defecate
S This causes contraction of rectal muscles, relaxation of the
anal sphincter, and contraction of the external anal
sphincter
Defecation Reflex
S If not acted upon, fecal matter returns to the colon via
reverse peristalsis
S Water is reabsorbed from fecal matter in the colon
S If defecation is prolonged for too long, constipation can
occur
S If defecation occurs too quickly, diarrhea will occur
Defecation Reflex
S Defecation is normally assisted by taking a deep breath and
trying to expel this air against a closed glottis
S The Valsalva Maneuver aids in creating pressure in the chest
such that the thorax exerts pressure on the digestive tract in
the abdomen
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