Question 9: the correct answer is O−. Got it right? Award yourself 1 point.
Question 10 of 10
How many pairs of chromosomes does a typical human cell have?
Then, in question 9: Which blood type is called the universal red cell donor?
The answer is O negative. Red blood cells of this type lack the A, B and Rh markers, which would trigger a reaction in the blood of the recipient. That is why they are used in emergencies, when there is no time to check the patient's type.
Blood groups
Types A, B, AB and O depend on markers on the surface of red blood cells. The system was described in 1901 by the Austrian Karl Landsteiner, who received the Nobel Prize in Physiology or Medicine in 1930 for the discovery.
The plus or minus sign indicates the Rh factor, another marker. In Brazil, most people are Rh positive, and O positive is the most common type.
For plasma, the liquid part of the blood, the rule is reversed: the universal donor is type AB, because its plasma has no antibodies against either A or B.
A blood donation takes only a few minutes and can help several people, because blood is separated into red cells, plasma and platelets. Blood centers inform who can donate and how often.
