Name any five
acid write their
sources
and
their significance for
our body in Tabular form.
Answers
Explanation:
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Explanation:
Maintenance of the internal environment is one of the vital functions (it has same importance as circulation or respiration). In Subchapter 7/6 is pointed out that maintenance of stable pH, also called isohydria, is one of the basic components of the internal environment: (1) isohydria, (2) isovolumia (stable volume), (3) isoosmolarity (stable tonicity), and (4) isoionia (stable ion composition).
Proton concentration and pH
Maintaining of stable anion and cation concentrations in blood plasma is denoted as isoionia. Maintaining of constant proton (H+) concentration is isohydria. pH is used for express concentration of the protons:
pH = – log c(H+)
Plasma and extracellular space concentrations of the protons are held in very narrow physiologic range. There is 40 nmol/l of protons in the arterial blood physiologically (note that concentrations of other plasma ions, e.g. [Na+] = 140 mmol/l or [HCO3–] = 25 mmol/l, are three orders of magnitude higher). pH could be easily calculated as follows:
pH = -log 40 x 10-9 mol/l
pH = 7,4
Physiologic range of the pH is 7,36-7,44.
Value of pH higher than 7,44 in arteries is denoted as alkalemia, pH lower than 7,36 is acidemia. Extensive deviations of pH value can cause serious consequences. For example change of protein structure (i.e. enzymes), membranes permeability, and electrolyte distribution. Value of pH in arterial blood higher than 7,8, resp. lower than 6,8 are incompatible with life.
Values mentioned above apply for arteriablood. Values differ in different body compartments hence there are different H+ concentrations. There is quite variable and lower pH value intracellular, it is about 7,0 ([H+] = 100 nmol/l). Intracellular pH compared to arterial pH gives difference 0,4. This corresponds to fact that there is 2,5 fold difference between intracellular and arterial H+ concentration. This concentration gradient drives the movement of H+ from cells to blood. Therefore it is not surprising that venous pH and pH of interstitial fluid is lower (i.e. more acidic) than arterial pH. Approximate value is 7,35.
Acids and bases in the body
Acid is defined as molecule that can cleave off H+ (Arrhenius) or donor of H+ (Brönsted). Base is au contraire molecule that can cleave off OH– (Arrhenius) or acceptor of H+ (Brönsted).
Source of acids in the body is chiefly metabolism, source of bases is predominantly nutrient.
Acids and bases undergo either (1) metabolic conversion (e.g. lactate to glucose in gluconeogenesis, lactate to pyruvate and oxidation in cardiomyocytes), or (2) excretion from body.
Three types of reactions can be distinguished from point of view of the acid-base balance. (1) proton-productive, (2) proton-consumptive, (3) proton-neutral. Examples follow:
1) Proton-productive reactions
a) Anaerobic glycolysis in muscles and erythrocytes
Glucose → 2 CH3CHOHCOO– + 2 H+
b) Ketogenesis – production of ketone bodies
Fatty acids → ketone bodies + n H+
c) Lipolysis
TAG → 3 FA + glycerol + 3 H+
d) Ureagenesis
CO2 + 2 NH+4 → urea + H2O + 2 H+
2) Proton-consumptive reactions
a) Gluconeogenesis
2 lactate + 2 H+ → Glc
b) Neutral and dicarboxylic amino acids oxidation
3) Proton-neutral reactions
a) Complete glucose oxidation
b) Lipogenesis from glucose
Human organism (healthy or not) every day produces great quantities of acids – source of protons. Organism is acidified by these processes:
1) Complete oxidation
Carbon skeleton → CO2 + H2O → HCO3– + H+
2) Incomplete oxidation
Carbohydrates → glucose → pyruvate, lactate + H+
Triacylglycerol → fatty acids, ketone bodies + H+
Phospholipids → phosphate + H+
Proteins → amino acids→ sulphate, urea + H+
Acids can be divided into two groups: (1) volatile acids (respiratory acids), (2) non-volatile acids (metabolic acids).
The most important volatile acid is carbonic acid (H2CO3). H2CO3 is produced by reaction of carbon dioxide (CO2 is acid-forming oxide) with water. 15 000 – 20 000 mmol CO2 (therefore same amount of carbonic acid) is produced every day. Respiratory system however very efficiently eliminates it. This justifies the term volatile acid.
kapitola_09_07-05