On the pH chart, label pH 1-14. Label neutral, acid range and base.
Definition of buffers?
How do buffers moderate pH change?
What is the composition of a buffer?
How does the Carbonic acid- Bicarbonate buffer system work where acid or base is added to it?
What happens to pH during hyperventilation?
Short Answer Question: Exercise will result in the production of CO2, which will acidify the blood. Explain the buffering system that minimizes blood pH changes.
The correct answer and explanation is :
pH Chart Labeling
- pH 1-14: A pH scale ranges from 1 (strong acid) to 14 (strong base).
- Neutral (pH 7): Pure water has a neutral pH of 7.
- Acidic Range (pH 1-6.9): Acids have a pH below 7 (e.g., stomach acid ≈ pH 1-2, lemon juice ≈ pH 2-3).
- Basic (Alkaline) Range (pH 7.1-14): Bases have a pH above 7 (e.g., baking soda ≈ pH 9, ammonia ≈ pH 11).
Definition of Buffers
A buffer is a solution that resists changes in pH when small amounts of acid or base are added. It helps maintain a stable pH in biological systems.
How Buffers Moderate pH Change
Buffers work by absorbing excess H⁺ or OH⁻ ions. If an acid is added, the buffer binds H⁺ ions to prevent the pH from dropping. If a base is added, the buffer releases H⁺ ions to neutralize excess OH⁻ and prevent the pH from rising.
Composition of a Buffer
A buffer is composed of a weak acid and its conjugate base, or a weak base and its conjugate acid.
For example:
- Carbonic Acid-Bicarbonate Buffer: H₂CO₃ (carbonic acid) / HCO₃⁻ (bicarbonate)
- Acetic Acid-Acetate Buffer: CH₃COOH (acetic acid) / CH₃COO⁻ (acetate)
Carbonic Acid-Bicarbonate Buffer System
The carbonic acid-bicarbonate system helps maintain blood pH (~7.4). It operates as follows:
- When acid (H⁺) is added:
- HCO₃⁻ (bicarbonate) binds H⁺ to form H₂CO₃ (carbonic acid), preventing pH drop.
- H₂CO₃ then breaks down into CO₂ and H₂O, which is exhaled.
- When base (OH⁻) is added:
- H₂CO₃ (carbonic acid) donates H⁺ to neutralize OH⁻, forming HCO₃⁻ (bicarbonate).
- This prevents the pH from rising.
Effect of Hyperventilation on pH
During hyperventilation, excess CO₂ is exhaled, reducing H₂CO₃ (carbonic acid) in the blood. This causes blood pH to rise (alkalosis).
Short Answer: How Exercise Affects Blood pH and Buffering
Correct Answer: The carbonic acid-bicarbonate buffer system helps stabilize blood pH by converting excess CO₂ (from exercise) into bicarbonate (HCO₃⁻) and carbonic acid (H₂CO₃), which can be exhaled as CO₂ or neutralized.
Explanation (300 words):
During exercise, the body’s metabolism increases, leading to the production of carbon dioxide (CO₂) as a byproduct of cellular respiration. CO₂ dissolves in blood and reacts with water (H₂O) to form carbonic acid (H₂CO₃):
[
CO₂ + H₂O \leftrightarrow H₂CO₃
]
Carbonic acid is weak and unstable, so it dissociates into bicarbonate (HCO₃⁻) and hydrogen ions (H⁺):
[
H₂CO₃ \leftrightarrow HCO₃⁻ + H⁺
]
The increase in H⁺ concentration lowers pH, making the blood more acidic. However, the carbonic acid-bicarbonate buffer system minimizes pH changes.
- If H⁺ levels rise (more acidic), bicarbonate (HCO₃⁻) binds to H⁺, forming H₂CO₃, which then converts into CO₂ and H₂O. CO₂ is exhaled through breathing, reducing acidity.
- If H⁺ levels drop (more basic), H₂CO₃ releases H⁺ to balance pH.
The respiratory system plays a key role in buffering by increasing breathing rate to remove CO₂ (reducing acidity) or slowing breathing to retain CO₂ (preventing alkalosis).
Thus, during exercise, this system ensures blood pH remains stable (~7.4), preventing harmful fluctuations in acidity.