pH (Potential of Hydrogen)
– pH is a measure of the acidity or alkalinity of a solution. It quantifies the concentration of hydrogen ions (H+) in a solution.
– The pH scale ranges from 0 to 14, with 7 being neutral. Values below 7 indicate acidity, and values above 7 indicate alkalinity.
Mathematical Expression:
pH = -log[H+]
Key Points:
1. Acidic Solutions:
– Have a pH of less than 7.
– Higher concentration of ( H+) ions.
– Common acids include hydrochloric acid (HCl) and citric acid.
2. Neutral Solutions:
– Have a pH of 7.
– Pure water is an example.
3. Alkaline or Basic Solutions:
– Have a pH greater than 7.
– Higher concentration of hydroxide ions (OH–).
– Common bases include sodium hydroxide (NaOH) and ammonia (NH₃).
4. Importance:
– pH is crucial for biological processes, enzymatic activities, and maintaining homeostasis.
Buffers
– Buffers are solutions that resist changes in pH when an acid or base is added.
– Composed of a weak acid and its corresponding conjugate base or a weak base and its corresponding conjugate acid.
Buffer Equation:
HA ⇌ H+ + A–
Key Points:
1. Buffering Capacity:
– Ability of a buffer to resist changes in pH.
– Maximal buffering occurs when concentrations of the weak acid and its conjugate base are approximately equal.
2. Common Buffers:
– Biological systems often use the bicarbonate ion HCO3– as a buffer in blood.
– Acetic acid (CH₃COOH) and acetate ion (CH₃COO⁻) form a buffer system.
3. Function:
– Buffers maintain a stable pH environment, which is crucial for biochemical reactions.
– Important in physiological systems to prevent rapid and drastic changes in pH.
Isotonic Solutions
Isotonic solutions have the same osmotic pressure as bodily fluids, resulting in minimal cell volume changes when cells are exposed to them.
Key Points:
1. Osmotic Pressure:
– Pressure exerted by solute particles in a solution influences water’s movement across a semipermeable membrane.
2. Isotonicity in Medicine:
– Intravenous fluids administered to patients are often isotonic to prevent cell shrinkage or swelling.
– Common isotonic solutions include Normal Saline (0.9% NaCl) and Lactated Ringer’s solution.
3. Red Blood Cells (RBCs):
– Isotonic solutions are vital for maintaining the shape and function of red blood cells.
– Hypotonic solutions cause RBCs to swell, while hypertonic solutions lead to cell shrinkage.
4. Cell Culture:
– Isotonic media are used in cell culture to maintain cell viability and function.
Understanding pH, buffers, and isotonic solutions is crucial in various scientific fields, from biochemistry to medicine. pH governs chemical reactions, buffers stabilize environments, and isotonic solutions maintain cell integrity in biological systems.
