4.7. Basic terms of acid-base balance. Buffer systems of the body. Parameters of acid-base balance. Flashcards
I. Basic terms of acid-base balance
1. What is the role of Acid-base balance?
Acid-base balance maintains a normal proton concentration in body fluids
=> This is achieved by utilization of buffers
I. Basic terms of acid-base balance
2. What are definitions of acid and base?
- Acid: any chemical that can donate H+
- Base: any chemical that can accept H+
I. Basic terms of acid-base balance
2A. What are volatile acids?
Volatile acids are defined as those acids which can be converted into a gaseous form and can thus be eliminated by the lungs.
=> Volatile acid in the body is mainly CO2.
-> In the reaction with carbonic anhydrase, CO2 is combined with H2O to make H2CO3 and eventually HCO3- + H+.
I. Basic terms of acid-base balance
2B. What are non-volatile acids?
A nonvolatile (fixed) acid is an acid produced in the body from sources other than CO2 and is not excreted by the lungs.
-> These acids are usually produced from amino acids with sulphur (makes sulphuric acid) and phospholipids (phosphoric acid).
-> As mentioned, they cannot be expired in the lungs, so they have to be buffered in the body and excreted in urine.
-> Overproduction of these acids can cause acidosis. (ex: lactic acid, formic acid, etc.)
I. Basic terms of acid-base balance
3. What is a Normal H+ conc.?
= 40 nEq/L, pH = 7.4
I. Basic terms of acid-base balance
4. What is the normal range of arterial pH?
o Normal range of arterial pH = 7.4 (less: acidemia, more: alkalemia)
I. Basic terms of acid-base balance
5. What is the Cytosol of a typical cell pH?
7.2
I. Basic terms of acid-base balance
6. What is the definition of pH?
pH – negative logarithm of hydrogen ion concentration (-log [H+])
I. Basic terms of acid-base balance
6A. What is the role of pH?
H+ affects biologically important molecules:
- Enzymes, receptors, ion channels, transporters, structural proteins
- If a protein gets protonated (HPr ⇌ H+ + Pr-), the ion concentrations will become very different
=> [K+] and [Ca2+] will especially be independent on PH
I. Basic terms of acid-base balance
7A. What is a buffer?
- A solution which resists changes in pH when a small amount of acids/bases are added to it
I. Basic terms of acid-base balance
7B. How is a buffer made?
Made of a mixture of a weak acid and its conjugated base OR a weak base and its conjugated acid (a strong acid/base would release the proton, and would not work in the physiological range)
=> Buffers should work close to the physiological range (to maintain blood pH = 7,35 to 7,45)
I. Basic terms of acid-base balance
7C. What is the optimal working range of buffer?
Buffers should work close to the physiological range (to maintain blood pH = 7,35 to 7,45)
I. Basic terms of acid-base balance
7D. Examples of buffers
- HCO3-/H2CO3 buffer is the most important buffer in the body ([HCO3-]= 23-25mM/L)
- Phosphate buffers are important in the urinary tract
- Proteins are important buffers. In the blood, the key ones are the albumin and hemoglobin
I. Basic terms of acid-base balance
7E. How can proteins work as buffers?
Proteins are important buffers. In the blood, the key ones are the albumin and hemoglobin
- Hemoglobin is not only for O2-transport, but also for CO2-transport
- In the Bohr effect: HHb ⇌ Hb + H+ (pH dependency of proton)
I. Basic terms of acid-base balance
7F. How can buffer limit pH-changes?
- If pH low: subject binding
- If pH high: subject releasing