A Level Biology Practice Exam

Which component is NOT found in the plasma?

1. Hormones

2. Glucose

3. Nerve cells

4. Electrolytes

The correct answer is: Nerve cells

Plasma, the liquid component of blood, acts as a transport medium for a variety of substances throughout the body. It contains a mixture of water, electrolytes, proteins, hormones, nutrients, and waste products. Nerve cells, however, are specialized cells that are primarily found within the nervous system, particularly in the brain and spinal cord. They do not circulate in the plasma. Instead, nerve cells communicate through electrical impulses and neurotransmitter release at synapses, which is fundamentally different from how substances like hormones, glucose, and electrolytes travel in the blood. Hormones act as chemical messengers and are transported in the plasma to target organs, glucose serves as a vital source of energy for cells and is also found dissolved in plasma, and electrolytes, such as sodium and potassium ions, are crucial for regulating various physiological functions and are present in plasma to help maintain osmotic balance and nerve function. Thus, nerve cells do not belong to the components typically dispersed in blood plasma, making the identified answer accurate.