Carbonic acid-bicarbonate buffer system

The bicarbonate-carbonic acid buffer system plays a major role in regulating the pH of fluids in tissue spaces outside blood vessels. This fluid, commonly referred to as interstitial fluid and separated from plasma by the membrane barrier known as the capillary endothelium, primarily... 

The solubihty of proteins in blood requires a pH in the range of 7.35 to 7.45. The bicarbonate-carbonic acid buffer system of blood (HCOj +... 

An average rate of metabolic activity produces roughly 22,000 mEq acid per day. If all of this acid were dissolved at one time in unbuffered body fluids, their pH would be less than 1. However, the pH of the blood is normally maintained between 7.36 and 7.44, and intracellular pH at approximately 7.1 (between 6.9 and 7.4). The widest range of extracellular pH over which the metabolic functions of the liver, the beating of the heart, and conduction of neural impulses can be maintained is 6.8 to 7.8. Thus, until the acid produced from metabolism can be excreted as CO2 in expired air and as ions in the urine, it needs to be buffered in the body fluids. The major buffer systems in the body are the bicarbonate-carbonic acid buffer system, which operates principally in extracellular fluid the hemoglobin buffer system in red blood cells the phosphate buffer system in all types of cells and the protein buffer system of cells and plasma. 

The buffer systems of the blood (mainly the bicarbonate/ carbonic acid buffer) minimize changes in pH. In acidoses, the bicarbonate concentration decreases to give a ratio of cHC03/cdC02 of <20 1. The respiratory compensatory mechanism responds to correct the ratio with increased rate and depth of respiration to eliminate CO2. Table 46-3 depicts expected compensation in both acidoses and alkaloses and corresponding laboratory values. 

One very important buffer solution is human blood An equilibrium between carbonic acid (H2CO3) and its conjugate base bicarbonate (HCOsi helps blood to maintain a relatively constant pH of around 7.4. The carbonic acid buffer system is created by carbon dioxide (CO2) dissolved in blood carbon dioxide reacts with water (H2O) to form carbonic acid. Since the amount of carbon dioxide in the blood depends on the rate at which you breathe, your blood pH is influenced by your breathing rate. Your body can... 

The important buffer system of blood plasma is the bicarbonate/carbonic acid couple ... 

The composite pA of the bicarbonate system, 6.1, may appear to make it ill-suited for buffering blood at physiologic pH of 7.4. Nevertheless, the system is very effective at buffering against additions of noncarbonic acids. Changes in the bicarbonate/carbonic acid ratio in such cases can be regulated by ... 

Blood travels through the human body in more than 96,000 km of blood vessels and it is full of marker molecules [34], The physiological pH is usually 7.4 with a complex buffer system (bicarbonate-carbonic acid, hemoglobinate-hemoglobin, phosphate buffer) [35],... 

Effect of Holding One s Breath on Blood pH The pH of the extracellular fluid is buffered by the bicarbonate/carbonic acid system. Holding your breath can increase the concentration of C02(g) in the blood. What effect might this have on the pH of the extracellular fluid Explain by showing the relevant equilibrium equation(s) for this buffer system. 

A description of acid-base balance involves an accounting of the carbonic (H2C03, HCOh COa", and CO2) and noncar-bonic acids and conjugate bases in terms of input (intake plus metabolic production) and output (excretion plus metabolic conversion) over a given time interval. The acid-base status of the body fluids is typically assessed by measurements of total CO2 plasma pH and PCO2, because the bicarbonate/carbonic acid system is the most important buffering system of the plasma. Occasionally, measurement of total titratable acid or base, or other acid and base analytes (e.g., lactate and ammonia [NH3]) is necessary to determine the etiology of an acid-base disorder. 

As was the case for the bicarbonate-carbonic acid system, the conjugate base form (HPO ) of the phosphate buffer is present in large (fourfold) excess compared to the acid form (H2PO4 ) and provides acid buffering capacity. Since the body metabolism produces more acid than... 

The body s buffering system can be divided into three components bicarbonate/carbonic acid, proteins, and phosphates. The bicarbonate buffer is the most important of the body s buffers, because (1) there is more bicarbonate present in the extracellular fluid (ECF) than any other buffer component (2) the supply of carbon dioxide is unlimited and (3) the acidity of ECF can be regulated by controlling either the bicarbonate concentration or the PCO2. 

The high water solubility of carboxylate salts is important in biological systems. The body s bicarbonate-carbonic acid and other buffer systems solubilize carboxylic acids by conversion to carboxylate salts. Intravenous drugs containing the COOH group are usually administered in the form of the carboxylate salt instead of the carboxylic acid to achieve faster absorption into the body. 

This sequence of reactions illustrates the buffering of the blood by the carbonic acid-bicarbonate conjugate acid-base system. The protons generated at the tissue level by the ionization of carbonic acid are removed at the lungs when bicarbonate ion reenters the red blood cell and reacts with them to produce carbonic acid. H2CO3 then rapidly dissociates, under the influence of carbonic anhydrase, and the resultant CO2 diffuses into the alveolar space because its concentration in the plasma is higher than in the alveoli. 

Immediate buffering of the blood uses bicarbonate/carbonic acid, as mentioned earlier. Removal of carbon dioxide through the respiratory system can help restore pH balance in the short term. Over a longer time, kidney-selective excretion of different ions is meant to restore blood pH levels to normal. 

Under the conditions of temperature and ionic strength prevailing in mammalian body fluids, the equilibrium for this reaction lies far to the left, such that about 500 CO2 molecules are present in solution for every molecule of H2CO3. Because dissolved CO2 and H2CO3 are in equilibrium, the proper expression for H2CO3 availability is [C02(d)] + [H2CO3], the so-called total carbonic acid pool, consisting primarily of C02(d). The overall equilibrium for the bicarbonate buffer system then is... 

Buffering refers to the ability of a solution to resist change in pH after the addition of a strong acid or base. The body s principal buffer system is the carbonic acid/bicarbonate (H2C03/HC03 ) system. 

Tissue culture, more frequently used as cell culture, enables animal and plant cells to be cultured in large numbers by techniques comparable to those used in microbiology but, because of the fragile nature of the cells, does require special cultural conditions. The culture media used must supply all the essential factors for growth, such as a wide range of amino acids, nucleotides, enzyme co-factors as well as indeterminate factors that can only be supplied in special products, e.g. foetal bovine serum. The environmental conditions must be carefully controlled, particularly pH, and this is frequently maintained by culturing in a bicarbonate buffer system and a carbon dioxide saturated atmosphere. 

The Henderson-Hasselbach equation allows the ratio of ionized un-ionized compound to be found if the pH and pKa are known. Consider carbonic acid (H2CO3) bicarbonate (HC03 ) buffer system... 

The buffering system for blood is based on carbonic acid (H2CO3) and its conjugate base bicarbonate (HC03 ) ... 

C. The carbonic acid-bicarbonate system is the most important buffer of the... 

The carbonic acid-bicarbonate buffer system has a of 6.1, yet is still a very effective buffer at pH 7-4 because it is an open buffer system, in which one component, CO2, can equilibrate between blood and air. 

One of the most important buffer systems in the human body is that which keeps the pH of blood around 7.4. If the pH of blood fall below 6.8 or above 7.8, critical problems and even death can occur. There are three primary buffer systems at work in controlling the pH of blood carbonate, phosphate, and proteins. The primary buffer system in the blood involves carbonic acid, H COj and its conjugate base bicarbonate, HCO3. Carbonic acid is a weak acid that dissociates according to the following reaction ... 

Daily body activities are quite sensitive to large pH changes, and must be kept within a small range of H30 and OH concentrations. Human blood, for example, has a pH of approximately 7.4 maintained by a buffer system. If our blood pH drops below 7.35, it can cause symptoms such as drowsiness, disorientation and numbness. If the pH level drops below 6.8, a person can die. To maintain pH stability, there is a carbonic acid - bicarbonate buffer system in the blood. 

The human body is a remarkable machine. It relies on a variety of safeguards to keep blood pH constant. Our blood constitutes a buffer system — meaning, it has components that can react with excess base or excess acid. Carbon dioxide, which is produced by the metabolism of food, dissolves in blood to produce carbonic acid, and carbonic acid can neutralize any excess base. The bicarbonate ion, also present in blood, will promptly take care of any surplus acid. The level of carbon dioxide in the blood adjusts to a body s rate of respiration. If blood pH drops — which actually means that the blood has... 

Blood plasma is buffered in part by the bicarbonate system, consisting of carbonic acid (H2C03) as proton donor and bicarbonate (HCO ) as proton acceptor ... 

Blood has several buffer systems that work together to maintain a narrow pH range between 7.35 and 7.45. A pH value above or below these levels can be lethal, primarily because cellular proteins become denatured, which is what happens to milk when vinegar is added to it. The primary buffer system of the blood is a combination of carbonic acid and its salt, sodium bicarbonate, shown in Figure 10.21. Any acid that builds up in the bloodstream is neutralized by the basic action of sodium bicarbonate, and any base that builds up is neutralized by the carbonic acid. 

Buffers stabilize a solution at a certain pH. This depends on the nature of the buffer and its concentration. For example, the carbonic acid-bicarbonate system has a pH of 6.37 when the two ingredients are at equimolar concentration. A change in the concentration of the carbonic acid relative to its conjugate base can shift the pH of the buffer. The Henderson-Hasselbalch equation below gives the relationship between pH and concentration. 

HA] is the concentration of the acid and [A-] is the concentration of the conjugate base. The pKa of the carbonic acid-bicarbonate system is 6.37. When equimolar conditions exist, then [HA] = [A ]. In this case, the second term in the Henderson-Hasselbalch equation is zero. This is so because [A ]/[HA] = 1, and the log 1 = 0. Thus at equimolar concentration of the acid-conjugate base, the pH of the buffer equals the pKa in the carbonic acid-bicarbonate system this is 6.37. If, however, we have ten times more bicarbonate than carbonic acid, [A ]/[HA] = 10, then log 10 = 1 and the pH of the buffer will be... 

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