1C - Water, Acids, Bases, and Buffers

What percentage of body weight is made up of water?

About 60%

List three functions of water in the body.

Dissolves and transports molecules, participates in chemical reactions, regulates body temperature.

What is the importance of water compartmentalization in the body?

It helps control molecule concentration, maintain homeostasis, and increase reaction probability.

Why is water a polar molecule?

Because electrons are shared unequally in the H-O bond, giving oxygen a partial negative charge and hydrogen a partial positive charge.

What allows water to dissolve polar substances?

Hydrogen bonding and the formation of hydration shells around ions.

Why are hydrogen bonds important in water?

They allow solutes to move, water to pass through membranes, and contribute to its solvent properties.

What are electrolytes?

Dissolved ions like Cl⁻, HCO₃⁻, K⁺, and Na⁺.

Define osmolality.

The total concentration of solutes dissolved in the blood.

How does water maintain osmolality in different compartments?

By moving to areas with higher solute concentrations (osmosis).

How is pH calculated?

pH = -log[H⁺].

What is the pH of pure water?

7 (neutral).

What is the normal pH range for blood?

7.35-7.45 (slightly alkaline).

How do acids and bases differ?

Acids donate H⁺ to solutions, while bases accept H⁺.

What makes a strong acid different from a weak acid?

Strong acids completely dissociate in water, while weak acids do not.

What does a higher Kₐ value indicate about an acid?

It has a greater tendency to dissociate.

What is a buffer?

A combination of a weak acid and its conjugate base that resists changes in pH.

When is a buffer most effective?

When pH = pKₐ (50% dissociation).

Why are buffers critical for the body?

They maintain pH stability in blood, cells, and tissues despite metabolic changes.

What is the major buffer system in the blood?

The carbonic acid-bicarbonate buffer system (H₂CO₃ ⇌ HCO₃⁻ + H⁺).

What enzyme assists in converting CO₂ to carbonic acid in blood?

Carbonic anhydrase.

Which buffer system is active inside cells?

The dihydrogen phosphate-hydrogen phosphate system (H₂PO₄⁻ ⇌ HPO₄²⁻ + H⁺).

What causes metabolic acidosis?

Excess ketoacids, lactic acid, or bicarbonate loss (e.g., diarrhea).

What causes respiratory alkalosis?

Hyperventilation, which lowers CO₂ levels.

How does respiratory acidosis differ from metabolic acidosis?

Respiratory acidosis is caused by CO₂ retention, while metabolic acidosis results from excess acids or bicarbonate loss.

In ketoacidosis, what happens to blood pH, CO₂, and bicarbonate levels?

pH drops (acidic), CO₂ is low, and bicarbonate is low due to buffering ketone acids.

Why does hyperventilation cause alkalosis?

Excess CO₂ is exhaled, reducing carbonic acid and increasing blood pH.