Video Transcript
What is the main function of blood plasma? (A) Binding to oxygen and transporting it to cells to be used in respiration. (B) Helping the blood clot in the arteries. (C) Targeting pathogens and fighting off infections. Or (D) transporting blood cells and other important substances around the body.
To answer this question, let’s review the components of blood and their functions so that we can determine the function of blood plasma. Blood is a vital fluid pumped by the heart to all parts of the body, supplying them with oxygen and nutrients and removing carbon dioxide and waste products.
As we can see in this diagram, blood has four main components: plasma, white blood cells, platelets, and red blood cells. Each individual component serves its own crucial function. Let’s look at each of these components and their functions, starting with red blood cells.
As you probably already know, human blood has a deep red color, which it gets from the hemoglobin that is found in red blood cells. Hemoglobin binds to and transports oxygen to all the body cells that require it for cellular respiration. If we take a look back at our options, we can see that this description matches option (A), binding to oxygen and transporting it to cells to be used in respiration. We can therefore eliminate this option, as this is the function of red blood cells, not blood plasma.
White blood cells are part of the body’s immune system. The main function of white blood cells is to target pathogens and fight off infections. This means that option (C), targeting pathogens and fighting off infections, cannot be the correct answer, because it clearly describes the function of white blood cells, not blood plasma.
Platelets are fragments of larger cells that play a role in blood clotting. If you’ve ever had a bleeding wound, you’ll have noticed that you lose some blood at first. But then the blood coagulates, and eventually a clot forms. The bleeding occurs when blood vessels are damaged and some blood leaks out. When blood vessels are broken in this way, platelets initiate clot formation at the damaged site. Clots are crucial to the body, as they help prevent excessive blood loss, which could otherwise be fatal. We now know that option (B), helping the blood clot in the arteries, is a function of the platelets and is therefore not our correct answer.
Now, let’s finally take a closer look at blood plasma. Blood plasma is straw yellow in color and composes over half of the volume of blood. As 90 percent of blood plasma is water, it functions effectively as the liquid medium of the blood, carrying all the other components of blood that we’ve learned about. Therefore, the main function of blood plasma, and the correct answer to this question, is answer option (D): transporting blood cells and other important substances around the body.
