Chemical Buffers 2. Explain buffer action in each of the following situations: i

Question

Chemical Buffers 2. Explain buffer action in each of the following situations: increased hydrogen ions / decreasing pH- decreased hydrogen ions / increasing pH - Role of Respiratory System The respiratory system regulates blood pH by controlling the amount of carbon dioxide in the blood. Explain. 3. Role of the Urinary System 4. Describe how the tubular cells of the PCT and collecting ducts (tubules) alter blood pH. Acid-Base Imbalances 5. a. Chemical buffers, the respiratory system, and the urinary system work together to maintain blood pH homeostasis. Identify the two main categories that cause pH imbalance.

Explanation / Answer

Q2) A buffer is a substance which minimizes the change in the pH of a solution. Usually buffers are a combination of a weak acid and a weak base, where the base is the anion ,which remains in the soultion after the weak acid gets dissociated (separates) to release H+ ions. It is a backward and forward reaction, where the buffer acts as a “friend” to H+ ions when required, or to OH- ions , maintaining a constant balance in the pH value.

For example - carbonic acid (H2CO3) is a weak acid. When it is put in a solution, a small amount of carbonic acid dissociates into H+ ions and the remaining bicarbonate anion (HCO3-). When there is increases H+ ion concentration and pH values lowers (towards acidic). The bicarbonate ion is a weak base because if there are lot of H+ ions in a solution, it will re-associate (chemically bind) due to excess H+ ions to reform the weak acid, it reduces the H+ ion concentration, as a result the pH value increases (back towards basic).

So buffers maintain the pH of a solution by adjusting the direction of their chemical reactions (dissociating or re-associating) based on the increase or decrease of H+ ion concentration taking place due to addition or removal of substances into the solution.

Q3)

Normal blood pH is 7.4,it is slightly alkaline. If the pH of blood drops below 7.2 or rises above 7.6 then very soon brain will stop functioning and the whole system will come to a halt. So blood pH below 6.9 or above 7.9 is fatal , if remains for a longer period.

Blood maintains it's pH level, pH is the concentration of hydrogen ions (H+). Buffers are molecules which take in or release ions in order to maintain the H+ ion concentration at a certain level. When there is more H+ ion concentration in blood the pH becomes low and blood becomes acidic ( causing acidosis). Buffers absorb these extra H+ ions. and if there is lack of H+ ions it causes the blood to be basic ( or causes alkalosis). In this situation, buffers release H+ ions. so buffers maintain the pH of our blood by either donating or taking H+ ions as per requirement to keep the number of H+ ions present in blood in right proportion.

In human body the mixture of carbon dioxide (CO2) and bicarbonate ions (HCO3) forms an important buffer. CO2 forms carbonic acid (H2CO3) when it is dissolved in water and acts as an acid giving up hydrogen ions (H+) when required. and HCO3 is a base which accepts hydrogen ions (H+) when there are more H+ ions. so blood pH is maintained by a balance between bicarbonate and carbon dioxide.

Bicarbonate Buffer System.- This is an important system in our bodies which maintain homeostasis.

CO2 + H2O <---> H2CO3 <---> (H+) + HCO3

If pH is too high, carbonic acid will donate hydrogen ions (H+) and pH will drop.

If pH is too low, bicarbonate will bond with hydrogen ions (H+) and pH will rise.

so too much CO2 or too little HCO3 in the blood causes acidosis. The CO2 level in body increases when there is hypoventilation or slow breathing in conditions like pneumonia. Bicarbonate gets lowered by ketoacidosis, a condition which occurs due to excess fat metabolism (diabetes mellitus).

Too much HCO3 or too little CO2 in the blood will cause alkalosis. This condition is less common than acidosis. CO2 can be lowered by hyperventilation.

Q4) The kidneys monitor and regulate the levels of hydrogen ions (H+) and bicarbonate ions in the blood to control blood pH. H+ ions are produced as a natural byproduct of the metabolism of dietary proteins and gets accumulated in the blood . The kidneys excretes excess H+ ions into urine for elimination from the body. The kidneys also conserves bicarbonate ions, which act as important pH buffers in the blood.

Most of the fitrate solution is reabsorbed in the proximal convoluted tubule (PCT).As the concentration of Na+ in the filtrate solution is high (about the same as the concentration of Na+ in blood plasma), Na+ moves from the tubular fluid into the cells of the PCT. When there are many Na+ ions this takes place by the help of symporters. Symporters simultaneously helps passage through the PCT membrane of both Na+ and another substances / solutes. Other substances that are reabsorbed with Na+ in this way are glucose , amino acids, lactic acid, and bicarbonate ions (HCO3-). These then move through cells by diffusion or by other transport processes.

Bicarbonate (HCO3-) do not have a transporter, so its reabsorption takes place by a series of reactions in the tubule lumen and tubular epithelium. when there is acidosis, the tubular cells reabsorb more bicarbonate from the tubular fluid, and the collecting duct cells secrete more hydrogen and produce more bicarbonate, and ammonia production leads to an increase in the formation of the NH3 buffer.

In response to alkalosis, the kidneys excrete more bicarbonate by decreasing hydrogen ion secretion from the tubular epithelial cells, and lowering the rates of glutamine metabolism and ammonium excretion.

Q5)

Two Factors causes blood pH Imbalance they are

i) our intake of oxygen-carbon dioxide, and dietary habits.

“When food is metabolized and broken down, it leaves certain chemical and metallic wastes, when they combine with our body fluids, produce either acidic pH or alkali pH.some foods are “acid-forming” in nature, whereas others are “alkali-forming”.

ii) The second factor is our production, elimination, and stress.level.-

An overactive adrenal gland, the release of cortisol and aldosterone, building up of glucose, lactic acid, and ketones.lack of sleep, inflammation.also puts impact on pH imbalance in body.

An over active adrenal gland caused by high levels of stress can release a hormone called aldosterone into the blood stream causing large quantities of potassium to be excreted into the urine. Aldosterone also causes the excretion of magnesium into the urine. Stress and anxiety are the principal acid generators apart from the diet.

Acid-Base Disorders or pH imbalance occurs due to Acidosis and Alkalosis

Acidosis- When the blood has too much acid (or too little base), causes a decrease in blood pH.

Acidosis is excessive blood acidity due to overabundance of acid in the blood or a loss of bicarbonate from the blood (metabolic acidosis), or by a buildup of carbon dioxide in the blood which might be due to poor lung function or slow breathing (respiratory acidosis).

Alkalosis- when the blood has too much base (or too little acid), causing an increase in blood pH.

Alkalosis is excessive blood alkalinity ,caused by an overabundance of bicarbonate in the blood or a loss of acid from the blood (metabolic alkalosis), or by a low level of carbon dioxide in the blood which might occur due to rapid or deep breathing (respiratory alkalosis).

Metabolic acidosis occurs when the amount of acid in the body is increased through ingestion of a substance that is, or can be broken down (metabolized) to, an acid.

Metabolic alkalosis can develop when there is excessive loss of sodium or potassium that affects the kidneys' ability to control the blood's acid-base balance. For example loss of potassium sufficient to cause metabolic alkalosis may occur due to overactive adrenal gland or by the use of diuretics.

Respiratory acidosis occurs when the lungs do not expel carbon dioxide adequately.

Respiratory alkalosis occurs when rapid, deep breathing (hyperventilation) causes too much carbon dioxide to be expelled from the bloodstream.

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