Why is maintaining acid-base balance important in the blood?
It ensures high levels of oxygen absorption.
It supports proper physiological functioning.
It prevents dehydration at the cellular level.
It keeps body temperature within a normal range.
The Correct Answer is B
A. It ensures high levels of oxygen absorption: Oxygen absorption depends primarily on partial pressure gradients and hemoglobin affinity rather than systemic pH alone. While the Bohr effect describes how pH influences oxygen unloading, it is not the primary reason for acid-base homeostasis. Global physiological stability is the broader goal.
B. It supports proper physiological functioning: Enzymes and membrane proteins require a specific narrow pH range to maintain their tertiary structure and catalytic activity. Significant deviations can lead to protein denaturation, metabolic failure, and lethal arrhythmias. Maintaining a pH of 7.4 is vital for all cellular operations.
C. It prevents dehydration at the cellular level: Fluid balance and osmolarity are the primary determinants of cellular hydration rather than the concentration of hydrogen ions. While acidosis can accompany severe dehydration, pH regulation does not directly manage water movement. Osmotic gradients are managed by electrolytes like sodium.
D. It keeps body temperature within a normal range: Thermoregulation is managed by the hypothalamus through sudomotor activity and vasomotor changes, independent of the bicarbonate buffer system. Acid-base disturbances may result from thermal stress but are not the mechanism of temperature control. These are distinct homeostatic pathways.
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Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
A. To raise pH by producing hydroxide ions: Biological buffers typically utilize bicarbonate or phosphate ions to neutralize excess acidity rather than generating hydroxide. Their goal is to maintain a stable pH of 7.4, not necessarily to make the blood more alkaline. They respond to both acidic and basic shifts.
B. To neutralize hydrogen ions by temporarily storing them: Buffers function by binding free protons when they are in excess and releasing them when the concentration drops. This "chemical sponge" effect prevents sudden fluctuations in the concentration of free hydrogen ions. This buys time for the lungs and kidneys to eliminate the excess.
C. To eliminate acids through the skin: The primary routes for acid elimination are the respiratory system for carbon dioxide and the renal system for fixed acids. The skin is not a major organ for acid-base regulation. Buffers operate internally within the plasma and intracellular compartments.
D. To convert weak acids into strong acids: The physiological goal of a buffer is the exact opposite; it converts strong acids into weak acids. By doing so, it reduces the total amount of free, active hydrogen ions in the solution. Converting to strong acids would cause dangerous drops in pH.
Correct Answer is B
Explanation
A. It measures the volume of blood plasma only: Osmolality refers to the concentration of particles per kilogram of solvent rather than the total volume of the compartment. Volume is a quantitative measure of space, while osmolality is a qualitative measure of solute density. These are distinct hemodynamic parameters.
B. It is influenced by the balance of solutes and water in the blood: The ratio of dissolved particles, primarily sodium, glucose, and urea, to the volume of water determines the osmotic pressure. High water intake decreases osmolality through dilution. Conversely, water loss through perspiration or diuresis increases the concentration of these solutes.
C. It has no relationship to hydration status: Plasma osmolality is the primary physiological indicator used by the hypothalamus to monitor hydration. Rising osmolality triggers the thirst mechanism and the release of antidiuretic hormone to conserve water. It is the most sensitive marker for systemic water balance.
D. It varies greatly in healthy individuals: Homeostatic mechanisms maintain plasma osmolality within a very narrow range, typically 280 to 295 mOsm/kg. Tight regulation ensures that cells do not experience osmotic shock or volume shifts. Significant variations usually indicate underlying pathological states or severe dehydration.
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