Section 1 Flashcards
Why is it crucial to maintain the body’s acid-base balance within narrow limits?
Maintaining the body’s acid-base balance within narrow limits is crucial to ensure homeostasis and support life.
Even slight changes in pH or the concentration of H+ can have detrimental, and sometimes fatal, consequences on bodily functions.
When pH fluctuates outside the normal range, the body has compensatory mechanisms in place to restore normal plasma pH, ensuring homeostasis is maintained.
What are buffer systems, and what is their role in the body?
Buffer systems are systems that help maintain a stable concentration of hydrogen ions (H+) in the body’s fluid. Their role is to resist changes in pH by accepting or donating hydrogen ions as needed.
Besides buffer systems, what other organs are essential for regulating both [H+] and [HCO3-]?
The lungs and the kidneys are also essential in regulating both [H+] and [HCO3-] in the body.
What are acids?
Acids are defined as hydrogen-containing substances, that when in solution, dissociate into H+ and an anion*.
Although many substances contain hydrogen, they are not necessarily classified as acids if their hydrogen is very tightly bound such that it does not separate from the molecule
E.g. HCl and H2CO3
How is a strong/weak acid determined?
Depending on the degree to which H+ disassociates (more H+ disassociating = stronger acid)
What is a base?
A substance that binds free H+ and removes it from the solution. Stronger base = more easily binds to H+
What is the term pH used to describe, and what is the equation for it?
pH is the amount of H+ in a solution
pH = log10(1/[H+])
or = -log([H+])
What is the normal pH of arterial blood and venous blood, and the normal blood pH?
Arterial blood = 7.45
Venous blood = 7.35
Average between the two = normal blood pH = 7.4
What is defined as acidosis or alkalosis?
When the blood pH falls below 7.35 = acidosis
When the blood pH rises above 7.45 = alkalosis
Severe changes in pH are not compatible with life, a pH less than 6.8 or more than 8.0 will result in death within a few seconds
What 3 effects do large changes in pH have?
- Effect on nerve and muscle cells: Acidosis suppresses the central nervous system, leading to disorientation, coma, and potential death. Alkalosis can cause over-excitability of both the central and peripheral nervous systems, potentially leading to death from spasms of respiratory muscles or convulsions.
- Effect on enzymatic reactions: Most enzymes in the body function optimally at a pH of 7.4. Changes in pH can speed up or slow down enzymatic reactions, with potentially deleterious consequences.
- Effect on potassium (K+) levels: Changes in [H+] can impact K+ levels in body fluids. Acidosis leads to more H+ being secreted than K+, resulting in increased plasma K+. Elevated plasma K+ levels can depolarize excitable cells, making them more excitable.
Where is H+ produced in the body? (Three primary sources)
- Carbonic acid formation: During cellular respiration, carbon dioxide (CO2) and water (H2O) combine in the presence of carbonic anhydrase to form carbonic acid (H2CO3), which dissociates into bicarbonate (HCO3-) and H+.
- Inorganic Acids Produced from Breakdown of Nutrients: Dietary proteins, rich in sulfur and phosphorus, can break down to form strong acids such as sulfuric acid and phosphoric acid, contributing to the free pool of H+ in the body.
- Organic Acids from Intermediary Metabolism: Examples include fatty acids produced during fat metabolism and lactic acid produced in muscles. Despite being weak acids, they still dissociate and contribute to the free pool of H+ in the body.
Describe the regulation of H+ for carbonic acid formation
In the tissues where CO2 is produced, the reaction is driven forward to produce more H+.
In the lungs where CO2 is removed, the reaction is driven backwards to reduce H+.
As long as respiration balances metabolic activity, there is no net increase or decrease in H+
