Health risks associated with being underweight include which of the following? Select all that apply.

A. While iron plays a role in certain enzymatic reactions in the body, its primary function is not directly related to nervous system function. Nervous system health depends on other nutrients like B vitamins, particularly B12.

B. Iron is essential for oxygen transport in the body. It is a key component of hemoglobin in red blood cells and myoglobin in muscle cells. Hemoglobin binds oxygen in the lungs and carries it to tissues throughout the body, while myoglobin stores and delivers oxygen within muscle cells, supporting energy production during physical activity. Adequate iron is critical for endurance, performance, and preventing fatigue. Iron deficiency can lead to anemia, decreased oxygen-carrying capacity, and impaired physical performance.

C. Iron is not directly used to generate energy from carbohydrates. Carbohydrates are metabolized via glycolysis and the Krebs cycle to produce ATP, but iron’s role is indirect, mainly as a component of hemoglobin and iron-containing enzymes that support oxidative metabolism.

D. While iron deficiency can indirectly affect blood oxygenation and overall cardiovascular function, iron does not directly maintain blood volume or blood pressure. Blood volume is regulated by water balance and electrolytes, while blood pressure depends on vascular resistance, cardiac output, and fluid status.

A. Hemoglobin is an iron-containing protein found in red blood cells. Its main role is to bind oxygen in the lungs and deliver it to tissues while carrying carbon dioxide back to the lungs for exhalation. Hemoglobin is a component of erythrocytes, not the fluid portion of blood.

B. Plasma is the straw-colored fluid portion of blood and constitutes approximately 55% of total blood volume. Plasma is about 90% water and contains essential substances such as: proteins (albumin, globulins, fibrinogen), electrolytes (sodium, potassium, calcium), nutrients (glucose, amino acids, fatty acids), hormones, and metabolic waste products (urea, carbon dioxide). Plasma serves multiple vital functions: it acts as a transport medium for blood cells, nutrients, hormones, and waste products; helps maintain blood pressure and volume; plays a key role in coagulation and immunity; and supports the body’s acid-base balance.

C. Lymph is a fluid that circulates within the lymphatic system. It carries immune cells, removes excess interstitial fluid from tissues, and returns it to the bloodstream. While plasma and lymph are similar in composition, lymph is not part of the circulatory blood system and does not constitute the fluid portion of blood.

D. Platelets, or thrombocytes, are small cell fragments responsible for blood clotting. They circulate suspended in plasma but are not the fluid portion themselves. They participate in hemostasis and wound repair.