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SIUE Buffers

Don's lecture 9/28 Chem & Physics applied anesthesia

pH scale 0-14
pH scale is called Power of hydrogen, measure of acidity or alkalinity
Neutral solution hydrogen ions = hydroxide ions
pH of pure water 7
Hydronium H30+ we look at it as H+ or acidd
Hydroxide OH-
Tap H20 pH is less than 7 because more acidic because if it's in the atmosphere CO2 dissolves in it. CO2 + H20 = H2CO3 or carbonic acid
Water equalibrium prinicple assumes that H20 is neutral. Always equal exponent of -14.
What ions are present in any solution H+ & OH-
Excess H+ means acidic solution
Excess OH- Basic solution
Acids produce H+ ions,pH > 7
increased pH alkalosis (reverse logarithmic represenation of H+)
decreased pH acidosis
Acid definition any substance that when dissolved in water, gives the solution a pH > 7. (b/c gives up H+ ion, H+ ion causes acidity)
Acids are tyipcally (characteristics) water-souble and sour tasting
Arabic Azait means oil, viscous. ACID
Latin acere means sour - ACID
Acid reactions able to give up proton (H+) to a base or accept an unshared pair of electrons from a base.
Acid reacts with a base in neutralized reaction (H20) to form a salt
Salt is an ionic compound composed of cation (+, Na) and an anion (-, CL) which ends up being neutral or no net charge.
Salt consists of a base and an acid
NH3 + HCL (ammonia and hydrocloric acid) = ? NH4CL (ammonium chloride) which is neutral
If chemical compound absorbs a hydronium (H+) ion (or is a proton acceptor) it is an alkaline
A base reduces concentration of _____ in H20 H30+ (or hydronium)
A base will reduce the concentration of H+ ions
Bases are less viscous than acid, have soapy touch, and bitter tasting
When acid is poured into water it? ex (HCL in H20 =) Gives up H+ to the water, giving H and Cl-
Strong acid will approaches 1, dissociates quickly
When a base is poured into water, it gives up OH
Neutralization mixing an acicd and base together (form pure H20 and salt)
If you have a strong acid and strong base pH = pH = 7
If you have weak acid and weak base pH = which ever is stronger, if acid is stronger, pH > 7, if base is stronger pH < 7.
Conjugate pairs only differ by a proton (or H+). Each acid has a conjugate base, and vice versa
HCL is conjugate pair because H+ acid, and CL- base
The key to regulating pH iss regulating hydrogen (H+) ion concentration
H+ ions are normally regulated by buffer systems
Extracellular fluid (ECF) is buffered by HCO3/CO2 renal & lungs
Intracellular fluid (ICF) is buffered by protiens and PO4
Tissue pH is typically lower than blood pH because metabolic processes create CO2 and lactic acid, and carbonic acid which equals more acid
Carbonic Acid is H2CO3, results from metabolism of carbs and fats (this metabolism produces 15,000 mmol of CO2/day)
Non-carbonic acid is a result of protien metabolism
Buffer prevent major changes in pH by removing or releasing H+ ions
Buffers can be classified into 3 MAIN groups 1.) chemical buffers (blood) 2.) respiratory CO2 3.) metabolic (or kidneys) HCO3-
Respiratory buffers (CO2) react within minutes
Chemical buffers in cells and body fluids react immediately
Metabolic (kidneys) buffers react in (HCO3)- hours to days
Acid-base homeostastasis centers around the regulation of the three main buffer systems (blood, resp, kidneys)
The HCO3-/CO2 buffer is present at the highest concentrations in the body, pKa value of 6.1 makes it a good pH. It's major components HCO3- & CO2 can be independantly related by the kidneys and lungs
Dietary intake, normal caloric inaked of a MEAT-based diet is about and controlled by 20,000 mEq of acid/day. CO2 as end-product of carb & fat metab (H2CO3 = H20 + CO2). CO2 is excreted by the lungs
Dietary intake of protein is 50-60 mEq/day of inorganic acids controlled by the kidney, excreted by kidney with HCO3 formation
Bicarb buffer system H + HC03 = H2CO3 = CO2 + H20 (an increase in H will bind with bicarb (HCO3) with the help of carbonic anhydrase) forming carbonic acid (H2CO3) which is immediately broken down into H20 & CO2, and lungs blow off the CO2 (OR ACID)
In the bicarb buffer system an increase in H+ leads to an increase in CO2 (which causes increased RR)
In the bicarb buffer system a decrease in H+ or (alkalinity) leads to a decreased in CO2 (which slows RR)
The respiratory system compensates in bicarb buffer system by changing rate & depth of RR in accordance with H+
Renal system a decrease in pH causes the kidneys to produce more HCO3 as well as increase secretion of H+ in the urine.
Renal system: an increase in pH causes the kideny to reabsorb the H+ back into the blood as well as excreting excess bicarb in the urine
Hemoglobin buffer system part I. prevents free CO2, and drastic changes in plasma CO2 because as the blood leaves tissues from oxygenation and other metabolic issues, the RBC snatches up the CO2 and quickly changes it to carbonic acid which dissociates easily to H+ and HCO3.
Hemoblobin buffer system part II. (H2CO3 dissociates into HCO3 & H) After dissociation, the bicarb (HCO3 & H) can be transported into the blood through circulation. So Bicarb moves to the plasma (H+ stays in rbc), Cl- shifts into RBC. Transported to lungs like this. Then, Bicarb moves back into the cell & CL- to plasma.
Hemoglobin buffer system part III. (in lungs after HCO3 moves into RBC) When HCO3 (bicarb) movese back into the RBC it combines with H+. (H + HCO3 = H2CO3 = CO2 & H2O) CO2 then leaves the RBC and goes out into the lung where it is breathed off.
Cl- plasma levels will be higher in arterial or venous blood Cl- plasma levels will be higher in the arterial blood sample.
Carbonic acid can only be formed or broken down by carbonic anhydrase, very unique enzyme found only in RBCs!
Respiratory buffer system goes from muscle to blood plasma, to lungs. Goal to keep CO2 level stable. carbonic acid/bicarb system. CO2 + H20 = H & HCO3 = CO2 & H20
Phosphate buffer system works best for intracellular fluid and urine Na2HPO4 = 2Na + HPO4 + H. Can absorbe free hydrogen.
Maintain of pH (receptors) Blood (carotid & aortic sinus), CSF (receptors in medulla), changes in RR depth & rate.
Narcotics blunt increased CO2, b/c pt is'nt taking a deep breath.
H+ secreted into renal tubules (meaning H+ excreted in urine) stops at pH 4.5, however other buffer systems keep pH high enough to continue secretion (like phosphorus)
What is biggest problem; elimination of excess base or acid? ACID
2 forms of acides Volitile (H2CO3) & non-volatile (products of metabolism)
Increased metabolic states like an increase in metabolism of carbs and fats you need more O2 so there is also an increased in CO2 as well (supply & demand).
Volatile acid more gas, H2CO3 (from fats and carbs) considered a weak acid that doesn't release H+ easily. Needs carbonic anhydrase for dissociation (found in RBC) so elimination is done in the lungs
Non-volatile acid products of metabolism, like H2SO4 & H3PO4 from metabolism of sulfucont proteiins & phospholipids, lactic acid/ketoacids. Eliminated by the kidneys.
When excess acid or base is introduced to the body it is immediately buffered to minimize the changes in pH
good buffer should be around 7.4
if you add H+ to the body you need to add A- (base)
if you take away H+ you need to add HA- (acid & base) inorder to replenish the H+
Good buffer has Equal parts; HA (acid) = A- (base)
pKa is parts in a certain place. A measure of tendency of a molecule or ion to keep a proton (H+)
Strong acids will completely or hardly dissociate in a solution? completely (give up a H+ easily)(HCL, pH of 2 = 0.01), have acidity constants close to 1
Weak acids do not fully dissociate (H2CO3), have acidity constants far less than 1. Soda has pH of 4 = 0.0001
H+ move freely between ECF & ICF, crossing BBB (otherwise the medulla would be useless)
movement of H+ must be matched meaning negatively charged ion (anion) in the same direction. Positively charged ions (cation) move in the opposite direction H+ enteres the cell, K+ exits the cell
Hgb is one of best protein buffers because it contains the most amount of histadines, which are amino acids that buffer H+ quickly.
Phosphate buffer pka 6.8. most acts ICF & KIDNEYS
Bicarb regenerated by bone stores of carbonate, although not enough to keep up with the loss. As we rid acid when breath off, we also loose the HCO3, so, the kidney is able to regenerate new bicarbe to replace loss.
Renal buffering, specialized buffering systems CO2 + H20 = H2CO3 = H + HCO3-, H+ is secreted into renal tubule where it is further buffered by phosphate & ammonia which maintains pH so that kidneys continue to excrete H+ in the urine if neccessary. H+ is secreted, HCO3- is reabsorbed into plasma.
Phosphorus in the kidneys binds to binds to H+, raising kidney pH above 4.5, so that kidneys continue to secrete H+ ions. Otherwise kidneys stop when pH reaches 4.5.
Created by: asaranita