Regulation of Body pH and Hydrogen Ions

Flashcards covering the importance of hydrogen-ion regulation, the pH scale, typical pH values of body fluids, buffering systems, and respiratory and renal mechanisms that maintain homeostasis.

What is another common name for the hydrogen ion in physiology?

A proton

Why must hydrogen ion concentration be tightly regulated?

Because excess free H⁺ can denature proteins and disrupt their function

Give three examples of proteins whose function can be impaired by pH changes.

Ion channels, receptors, enzymes (also antibodies, ligands, hemoglobin)

Which pH values are classified as acidic on the pH scale?

Any pH below 7 (0–6.99)

How does pH relate to hydrogen ion concentration?

Lower pH means higher [H⁺]; each whole-number step is a 10-fold change

Mathematically, how is pH defined?

pH = –log₁₀[H⁺] or log₁₀(1/[H⁺])

What is the normal pH range of extracellular fluid (blood plasma/interstitial fluid)?

Approximately 7.38–7.42 (slightly alkaline)

What is the typical pH range of gastric juice and why is it so low?

About 1.4–3.5; acidity aids immunity and protein digestion

What is the pH range of human skin and why is it acidic?

4.7–5.7; the acidity deters pathogens

How variable is urine pH and what governs that variability?

Ranges from 4.5 to 8.5 depending on renal excretion of acids or bases

What are the three major physiological mechanisms that regulate body pH?

Buffers, ventilation (respiratory system), and renal excretion (kidneys)

Why are free hydrogen ions more dangerous than hydrogen atoms bound in molecules like water?

Only free H⁺ can interact with and disrupt biochemical processes

Name the two principal intracellular buffer molecules.

Phosphate ions and hemoglobin

What is the main extracellular buffer in blood plasma?

Bicarbonate ion (HCO₃⁻)

Roughly how much more bicarbonate than hydrogen ions exists in blood plasma?

About 600,000 times more

Write the reaction that links CO₂ to hydrogen ion production.

CO₂ + H₂O ⇌ H₂CO₃ ⇌ HCO₃⁻ + H⁺

How does increasing carbon dioxide affect extracellular pH?

It raises [H⁺] and lowers pH (makes it more acidic)

Which peripheral chemoreceptors detect high CO₂/H⁺ and stimulate ventilation?

The carotid bodies in the carotid arteries

What extracellular fluid pH levels are incompatible with life?

Below 7.0 or above 7.7

How do the kidneys help maintain pH homeostasis?

By secreting/excreting excess H⁺ in urine