cellular response to pH

Definition

Target type: biologicalprocess

Any process that results in a change in state or activity of a cell (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of a pH stimulus. pH is a measure of the acidity or basicity of an aqueous solution. [GOC:mah, Wikipedia:PH]

Cellular response to pH is a complex process that involves a variety of cellular mechanisms to maintain pH homeostasis. Cells must tightly regulate their internal pH to ensure optimal function of enzymes, proteins, and other cellular components. Fluctuations in pH can disrupt cellular processes and lead to cell death.

The pH of the intracellular environment is typically slightly alkaline, ranging from 7.2 to 7.4. However, different cellular compartments may have different pH values. For example, the pH of lysosomes is acidic, around 4.5-5.0, which is essential for their digestive function.

Cells use a variety of mechanisms to maintain pH homeostasis, including:

* **Proton pumps:** These proteins transport protons (H+) across cell membranes, either into or out of the cell, to regulate pH. Examples include the Na+/H+ exchanger, the vacuolar H+-ATPase, and the plasma membrane H+-ATPase.
* **Carbonic anhydrases:** These enzymes catalyze the reversible hydration of carbon dioxide (CO2) to form carbonic acid (H2CO3), which can then dissociate into bicarbonate (HCO3-) and a proton (H+). This process is important for maintaining pH balance in the blood and other bodily fluids.
* **Buffer systems:** Buffers are molecules that can accept or donate protons, thereby resisting changes in pH. Important buffers in cells include bicarbonate, phosphate, and proteins.
* **Cellular signaling pathways:** Cells can respond to changes in pH by activating signaling pathways that lead to changes in gene expression or protein activity. These pathways can help cells adapt to changes in their environment and maintain pH homeostasis.

**Regulation of pH in the cytoplasm:**

* The cytoplasm is typically slightly alkaline.
* The Na+/H+ exchanger pumps protons out of the cell in exchange for sodium ions (Na+).
* The plasma membrane H+-ATPase pumps protons out of the cell.
* Carbonic anhydrase converts CO2 to HCO3-, which can be exported from the cell.

**Regulation of pH in organelles:**

* Organelles, such as lysosomes and endosomes, have specialized mechanisms for maintaining pH homeostasis.
* Vacuolar H+-ATPases pump protons into these organelles.
* Organic acids and bases are transported into or out of organelles to regulate pH.

**Response to acidic stress:**

* When the extracellular pH decreases, cells may activate mechanisms to buffer the pH change.
* The Na+/H+ exchanger and the plasma membrane H+-ATPase pump protons out of the cell.
* Carbonic anhydrase produces bicarbonate, which can be used to buffer the pH change.
* Cells may activate signaling pathways that lead to changes in gene expression, such as the activation of genes that encode for proton pumps or buffering proteins.

**Response to alkaline stress:**

* When the extracellular pH increases, cells may activate mechanisms to lower the pH.
* The plasma membrane H+-ATPase pumps protons into the cell.
* Cells may activate signaling pathways that lead to changes in gene expression, such as the activation of genes that encode for proton pumps or buffering proteins.

Cellular response to pH is essential for maintaining cell function and survival. Dysregulation of pH can lead to a variety of pathological conditions, including cancer, inflammation, and neurodegeneration.'
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Proteins (5)

Compounds (10)