How Nucleic Acids Go From Here To

There

By: Laura Capparilli, Tyler Horton, Zach Johnston, and Kim Hagey

DNA

Characteristics of DNA: double-stranded, double helix, antiparallel

Nucleic Acid: polymeric macromolecules made from nucleotide monomers

Nucleotide: An organic molecule that serves as a monomer of nucleic acid

Nucleoside: any various compound of sugar paired with either a purine or pyrimidine

RNA

Characteristics: single-stranded Uracil replaces Thymine

Bases: Purines and Pyrimidines

Purine: A nitrogen-containing substance derived from uric acid

Purine bases: Adenine and Guanine

Pyrimidine: A nitrogenous base with a six-sided structure

Pyrimidine bases: Cytosine, Thymine, Uracil

Base Paring in DNA: A=T, C=G

Base Pairing in RNA: A=U, C=G

Main functions: 1. DNA/RNA Replication 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

Ribonuclease - breaks down RNA into ribonucleotides

Chyme enters the duodenum, and the pancreas releases pancreatic juice which contain:

Deoxyribonuclease - breaks down DNA into deoxyribonucleotides

Digestion in the Small Intestine

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Further digestion occurs at the microvilli in the S.I. from two enzymes:

Phosphatases&Nucleosidases

Products of Digestion

So your final products are Phosphate ion, pentose sugars, and a nitrogenous base.

Duodenum and Jejunum absorb the products in the epithelial cells.

Absorption

Membrane transport proteins carry the products to the simple columnar using active and secondary transport.

Absorption

Diffusion of the products from the simple columnar epithelium across the basolateral membrane into the interstitial fluid, into the capillary.

Where the Pyrimidines and Purine bases undergo De-Novo Synthesis, the pathway, and Salvage Pathway

De-novo Synthesis

Why? Nucleic acids may not be readily available

De-novo synthesis is the creation of complex molecules from simpler molecules like sugars or amino acids

De-novo synthesis also refers to the process of DNA replication

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

The de-novo pathway does not use free bases (A,G,C,T,U)

De-novo Pathway

The purine ring is built up one atom or a few atoms at a time and attached to ribose throughout the process

The pyrimidine ring is synthesized as orotate (heterocyclic compound) and attached to ribose phosphate

The ribose phosphate is converted into common pyrimidine nucleotides

The enzymes involved in De-novo synthesis are present as large multienzyme complexes, such as folate, carbon dioxide, and glutamine.

Salvage Pathway

Bases and nucleosides are formed during degradations of RNA & DNA

The SALVAGE PATHWAY is used to recover these molecules

This is especially important in tissues that cannot undergo De Novo Synthesis

Salvage Pathway

Human Urate Homeostasis

Urate is produced as the major end product of purine metabolism by liver, muscles, and intestine.

The biosynthesis of urate is catalyzed by xanthine oxidase (XO).

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 DegredationGuanine and Adenine are converted to Uric Acid

Products of pathway

Nuclease frees the nucleotide

Nucleotidase frees guanosine

Guanosine is converted to guanine

Guanine converted to xanthine

Xanthine converted to uric acid

Hyperuricemia

An abnormally high level of uric acid in the blood.

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

Forceful attempted expulsion of air with plugged nose and closed mouth

Clears pressure in the middle ear

Valsalva Maneuver

4 stages:

1. Initial Pressure Rise

2. Reduced Venous Return and Compensation

3. Pressure Release

4. Return of Cardiac Output

Valsalva Maneuver

Valsalva Maneuver

Can help diagnose:

Cardiovascular issues

Neurological issues

Urogenital Problems

Valsalva Maneuver

Clinically, the Valsalva Maneuver is done against a closed glottis

This is a common sensation when exerting force such as lifting a heavy object or trying to force defecation

Defecation Reflex

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

The rectum ampulla (dilated section of the rectum where feces is stored until it is expelled) acts as a temporary fecal reservoir

As rectal walls stretch due to filling, stretch receptors stimulate the desire to defecate

This causes contraction of rectal muscles, relaxation of the anal sphincter, and contraction of the external anal sphincter

Defecation Reflex

If not acted upon, fecal matter returns to the colon via reverse peristalsis

Water is reabsorbed from fecal matter in the colon

If defecation is prolonged for too long, constipation can occur

If defecation occurs too quickly, diarrhea will occur

Defecation Reflex

Defecation is normally assisted by taking a deep breath and trying to expel this air against a closed glottis

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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