Video Transcript
The given diagram demonstrates the average percentages of the main components of blood in a sample. What component is label A representing?
When you go for a blood test, a small sample of blood is taken from one of your veins and collected in a test tube. It is then sent off to a laboratory, where a scientist uses a piece of equipment called a centrifuge to separate it out into its components. This is what you can see in the diagram. The three distinct layers represent the main components of the blood.
To answer this question, we first need to know what these components are and understand their functions. Let’s start at the bottom of the diagram and work our way up. The red layer contains red blood cells, which are also known by their scientific name, erythrocytes. Red blood cells make up around 45 percent of the total blood volume, and their main role is carrying oxygen. Remember, oxygen has the chemical formula O2 because it’s usually found as molecules made of two oxygen atoms. You can think of red blood cells as oxygen delivery drivers. They pick up oxygen at the lungs, travel all around the body in the blood vessels, and drop off the oxygen at cells which need it for aerobic respiration.
Now let’s look at the next layer. This one contains white blood cells and platelets, which together make up less than one percent of the total blood volume. White blood cells, which are also known as leukocytes, are part of the immune system. And their job is to fight off diseases by locating pathogens and removing them from the body. There are three main ways in which they do this. The first is by directly engulfing the pathogen before digesting it with enzymes. The second is by releasing antitoxins which neutralize harmful toxins produced by the pathogen. The third is by releasing antibodies which stick to the pathogen and alert the immune system that a potentially dangerous biological agent has entered the body and needs to be destroyed by other immune cells.
Platelets, also known as thrombocytes, are small cell fragments. They act alongside clotting factors to form blood clots and scabs, which stop wounds from bleeding and help to prevent pathogens entering the body.
The final component of the blood is the plasma. This makes up the largest percentage of the total blood volume at around 55 percent. Plasma is a straw-colored fluid, which is predominantly made of water but also contains proteins, ions, and nutrients, for example, glucose. Its function is to carry the three components we’ve already talked about, as well as to transport hormones like adrenaline, gases such as carbon dioxide, and waste products, for example, urea. Using this information, we can therefore deduce that label A is representing the plasma.
