Which of the following does blood NOT carry?

Blood is responsible for transporting a variety of substances throughout the body, including nutrients, oxygen, and carbon dioxide. It plays a crucial role in maintaining homeostasis and delivering essential components to tissues and organs to support metabolic processes.

Nutrients are carried in the plasma of the blood, providing cells with the energy and building blocks they require for growth and function. Oxygen is transported primarily by hemoglobin in red blood cells to vital tissues, while carbon dioxide, a waste product of metabolism, is also carried by blood, primarily dissolved in plasma and bound to hemoglobin.

Calcium ions, while essential for various physiological functions such as muscle contraction and neurotransmission, are not transported by blood in the same manner as nutrients, oxygen, or carbon dioxide. Instead, calcium is primarily found in the bone tissue and is regulated by hormones and other factors in the body. Thus, identifying that blood does not carry calcium ions distinguishes it from the other substances the blood transports.