7_25 Lecture 1 Byrnes acid_bases.txt
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- Channels that regulate permeability of cell membranes
Normal number of Hydrogen bonds on an H2O molecule
3 but max is 4
Blood plasma osmolarity and isotonic solution
286 mOsmolar solution or... the "active osmolarity"
What is the total osmolarity of plasma mainly dependent on?
Anion Gap Ions: Na+, Cl-, HCO3- and proteins contribute only 4% too.
What can alter plasma osmolarity
High Blood Urea (BUN) or Glucose. High blood ketoacids and hyperglycemia (high blood pressure) leads to water loss or dehydration that accompanies ketouria and glucosuria.
Plasma osmolarity equation
mOsm/L=2[Na+] + [glucose (mg/dL)]/18+ BUN(mg/dL)/2.8
What are the intracellular ions in order of magnitude
K+ > HPO4-- > Protein- > Mg++
What is the Blood Plasma Ions
Na+ > Cl- > HCO3- (these are the anion gap ions) and protein and also a LITTLE bit of the other ions like K+, Ca++, Mg++
What is in the interstitial Fluid?
Same as plasma except little protein... so.... Na+, Cl-, HCO3-, and the other little ions
Two Hormones controlling blood plasma Osmolarity and How?
Antidiuretic Hormone (ADH or Vasopressin) --- Renal H20 Retention; Aldosterone--- Renal Na+ Retention
What is Diabetes Insipidus, and what causes it?
Caused by a defect in the production of ADH. Thus, you can't retain H20
What can high sugar and salt intake lead to?
Higher urine secretion as the body is the body carries out the sugar/salt. Thus a loss of water and dehydration. This is called Diuresis
What is a pKa that characterizes a strong acid
Less than two... so a small pKa= strong acid. (90% ionization)
Examples of Strong acid/strong base
HCl, H2SO4, HNO3, NaOH, KOH.... (note that H3PO4 and NH3 are not strong).... Basically consists of a H+ or OH- and a "neutral" counterion.
Henderson-Hasslebalch Equation (both versions)
- pH= pKa + log[A-]/[HA]
- pH= pKa + log[salt]/[acid]
What is pKa
The concentration of the salt/ acid.... the ionization
What is pKa at 50% titration?
It is equal to pH... [salt]= [acid]
When should you use the H-H equation
useful for determining ratio at any pH or the pH from 10%-90% of the titration.
What is pH at the start of titration?
Simply the pH. So using the pKa you must figure out the concentration of H+ ... If it is a weak acid use the H-H equation because it does not fully ionize. Basically figuring out x^2/ [HA]= -pKa
What is a buffer made of?
A weak acid and one of its alkali or alkaline salts (Na or Ca)
What are the major protein Buffering groups?
COOH and NH3
List Protein Buffering groups in order of pKa
Alpha CooH < distal COOH < His imidazole < alpha amino < distal amino < Arg guanidyl
What is a molecule with both acidic and basic groups
What is a zwitterion
at physiological pH an amino acid that exist with no net charge near pH 7.0
What is a polyprotic acid
Multiple Acidic groups
What is a buffer's maximum capacity
- When pH = pKa.
- ie: when ... idk ha
What is isoelectric PH
- It's the pH when there is no net charge in the amino acid!
- pI or pHi
- = (pKa1 + pKa2 )/ 2
If 20 mmoles of aspartic acid (HCl salt) was titrated to pH 10, how many mmoles of NaOH(0.1 N) would be required? (pKa's: 2.1, 3.9, 9.8)
First draw the titration curve out and work thru it
Draw the Carbonic Acid Equation
CO2(gas) <--> CO2 (aq)
CO2(aq) + H2O <--carbonic anhydrase --> H2CO3
H2CO3 <--pKa6.1---> HC0-3 + H+
HCO-3 <---pKa10.2---> CO-3
What is PCO2 or the gas Tension of CO2
40 mm of Hg
What is the pKa of CO2, and Why isn't pKa of CO2 not ideally 7.4, the physiological pH?
- pKa of CO2 is 6.1
- CO2 is volatile in the open system (lungs)
- So original equation would be :
- pH= 6.1 + log [HCO3]/[H2CO3].... at pH=7.4 there must be a 20:1 ration (as log20= 1.3)
- the right equation would be
- pH= 6.1 + log[HCO-3] / alpha * PCO2
- alpha= solubility coefficient = .0301
- PCO2= 40
What is the volatile CO2 equation for pH?
pH= 6.1 + log [HCO3]/ alpha*PCO2
What is the solubility coefficent for CO2 (alpha)
What are 3 different forms CO2 is found in the blood, and rank them in order of their blood concentrations
- Total Blood CO2 = H2CO3 + HCO3 + CO3 (neglible)
- HCO3 > CO2 (aq) > H2CO3 > CO3
What are the major Plasma buffers. Rank them in blood concentration.
HCO3/CO2 > Hemoglobin > Plasma Proteins > Phosphate
Major CO2 carriers in the blood. Rank them in order of concentrations
HCO3/CO2 > Hemoglobin > Plasma Proteins
What's the effect of having a open system for CO2 in the lungs in terms of pH balance?
Having an open system allows for PCO2 to remain 40 mm of Hg. Thus, when an acid or a base is added, there is a very small change in pH.
In a closed system PCO2 will change and there would large changes in pH according to the equation pH = 6.1 + log [HCO3]/alpha*PCO2
What is Carbonic anhydrase or Dehydratase?
Enzyme essential for H2CO3 and HCO3 transfer. super fast!
How does breathing effect pH
Increased ventilation causes a decrease in H2CO3 or CO2 tension and an increase in pH.
Is Venous blood more acidic or basic? and why?
Venous blood is slightly more acidic due to the increased tension of CO2 gas carried from metabolism compared to arterial blood. This is the dynamic concept of "open" or physiological versus "closed" or "test tube" system.
How do the Kidneys regulate pH? lungs?
The kidneys control the HCO3 retention and release (the basic half of the equation). Whereas the lungs control the Carbon dioxide (the acidic half of the equation).
Hence the mnemonic pH= 6.1 + kidney/lung
But specifically, the distal side of the nephron works on H+ secretion. The proximal side works on NaHCO3 recovery
What's the difference between metabolic and respiratory disorders?
- Metabolic disorders effect the concentration of HCO3 (kidneys)
- Respiratory disorders effect the concentration of PCO2 (lungs)
How much HCO3 do the kidneys keep in the blood for physiological pH
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