Quiz & Worksheet - pH Balance in the Body | Study.com - Free Printable

Let's go through each question in the worksheet and solve them step by step, with explanations.

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Question 1:

Based on this diagram, what would happen if too much HCO₃⁻ entered the bloodstream?

The diagram shows the reaction:
> CO₂ + H₂O ⇌ H₂CO₃ ⇌ HCO₃⁻ + H⁺

This is the carbonic acid-bicarbonate buffer system, which helps regulate blood pH. The bicarbonate ion (HCO₃⁻) acts as a base and can accept hydrogen ions (H⁺). When too much HCO₃⁻ enters the bloodstream, it will bind to H⁺ ions, shifting the equilibrium to the left and reducing acidity — thus increasing blood pH.

This leads to an increase in blood pH, resulting in alkalosis.

Now, since bicarbonate is a metabolic component (produced or regulated by the kidneys), an excess of HCO₃⁻ indicates a metabolic cause, not respiratory.

So the correct answer is:

> d. Metabolic alkalosis

✔ Answer: d. Metabolic alkalosis

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Question 2:

In which case would the bottom reaction of the two shown below be advantageous to occur in the blood?

Reactions:
1. Na₂HPO₄ + HCl → Na₂H₂PO₄ + NaCl
2. NaH₂PO₄ + NaOH → Na₂HPO₄ + H₂O

These represent the phosphate buffer system in the blood.

- The first reaction neutralizes acid (HCl) by converting H₂PO₄⁻ into H₃PO₄ (but here written as forming Na₂H₂PO₄).
- The second reaction neutralizes base (NaOH) by converting H₂PO₄⁻ into HPO₄²⁻.

So:
- Reaction 1 occurs when blood is acidic (to remove excess H⁺)
- Reaction 2 occurs when blood is alkaline (to remove excess OH⁻ or add H⁺)

Therefore, the bottom reaction (which consumes base) is beneficial when the blood is alkaline.

✔ Answer: c. If the blood pH was alkaline

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Question 3:

Based on this diagram showing normal gas exchange, which of these conditions results in respiratory acidosis?

Respiratory acidosis occurs when there is excess CO₂ in the blood due to inadequate ventilation (i.e., not enough CO₂ is exhaled).

Let’s examine the options:

a. Hyperventilation → This causes excessive CO₂ loss → respiratory alkalosis, not acidosis.

b. Diabetes mellitus → Causes metabolic acidosis due to ketoacid production (not respiratory).

c. Intestinal malabsorption → Not directly related to CO₂ retention; may affect electrolytes but not typically cause respiratory acidosis.

d. Holding one's breath to dive under water → You're not breathing, so CO₂ builds up in the blood → increased CO₂ → increased carbonic acid → decreased pH → respiratory acidosis.

This matches the definition of respiratory acidosis: high CO₂ due to hypoventilation.

✔ Answer: d. Holding one's breath to dive under water

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✔ Final Answers:

1. d. Metabolic alkalosis
2. c. If the blood pH was alkaline
3. d. Holding one's breath to dive under water

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🔍 Summary Explanations:

- Metabolic alkalosis: Caused by excess bicarbonate or loss of acid (e.g., vomiting). Bicarbonate increases pH.
- Phosphate buffer system: Buffers both acid and base. Bottom reaction removes OH⁻/adds H⁺ → useful in alkaline conditions.
- Respiratory acidosis: Due to CO₂ buildup from poor ventilation (e.g., holding breath, lung disease).

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