AMT Medical Laboratory Scientist (MLS) Practice Exam

The correct answer is hydrogen ions, as they are the primary factor in determining the acidity or alkalinity of blood, which is expressed as pH. Blood pH is a measure of how acidic or basic the blood is, and it is influenced significantly by the concentration of hydrogen ions present in the blood. An increase in hydrogen ion concentration results in a lower pH (more acidic), while a decrease leads to a higher pH (more alkaline).

The regulation of hydrogen ion concentration is crucial for maintaining homeostasis within the body, and it is primarily managed through the lungs and kidneys. The respiratory system influences blood pH by adjusting the amount of carbon dioxide (which can react with water to form carbonic acid and subsequently release hydrogen ions) while the kidneys can excrete or retain hydrogen ions to help balance pH levels.

Other ions listed contribute to the buffering system or affect pH indirectly, but they do not directly determine blood pH. Sodium and chloride ions are involved in various physiological functions, including maintaining osmotic balance and facilitating nerve impulses. In contrast, bicarbonate ions play a significant role as a buffer in the blood, helping to neutralize excess acids or bases, but it is the presence of hydrogen ions that directly influences the p