Blood Trivia
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7correct to beat the crowd
This blood trivia quiz has 100 free questions with answers and covers the science and the stories of the roughly five litres flowing through you. It starts with the basics (what plasma is, how long a red blood cell lives, why blood is red, what platelets do, what the hematocrit measures) and moves through blood types and the discoveries of Karl Landsteiner, the grisly early history of transfusion, the first blood bank, and the diseases from anaemia and sickle cell to the 'royal disease' haemophilia. It also wanders into the natural world and history: the horseshoe crab's blue blood, the skinks with green blood, vampire bats and leeches, bloodletting and the barber's pole, William Harvey's discovery of circulation, and how blood pressure came to be measured. About a third of the questions are easy enough for a school biology class; the rest are for nurses, medics and hardcore quizzers. Every answer has been checked against Wikipedia's articles on blood, haematology and their history, and each question links to the page that confirms it.
30 of 100 questions with answers and explanations. Play the quiz
Q 01Roughly what percentage of an adult human's body weight is blood?
7%
7% is the textbook figure: blood accounts for roughly 7 to 8 per cent of adult body weight, and its density is only slightly greater than water's.
Q 02Roughly how much blood does the average adult have?
About 5 litres
About 5 litres of blood circulate in a typical adult; women average a little less than men, and the volume rises markedly during pregnancy.
Q 03What is the straw-yellow liquid that makes up about 55% of blood?
Plasma
Plasma is the straw-coloured fluid fraction of blood; serum is the name for plasma with the clotting proteins removed, and both are mostly water.
Q 04Which iron-containing protein in red blood cells carries oxygen?
Hemoglobin
Hemoglobin is a globin protein carrying iron-containing haem groups; it gives red cells their colour and makes up roughly a third of each cell's weight.
Q 05How many oxygen molecules can a single molecule of the red cells' oxygen-carrying protein bind?
4
4 is the maximum: each of the protein's four haem groups binds one oxygen molecule, and the reversible, cooperative binding is what makes transport efficient.
Q 06Roughly how long does a human red blood cell circulate before it is recycled?
100-120 days
100-120 days is the typical lifespan; worn-out red cells are broken down by macrophages, mainly in the spleen, and their iron is recycled for new cells.
Q 07Unlike those of birds, reptiles and fish, mature mammalian red blood cells lack what?
A nucleus
A nucleus is shed as mammalian red cells mature, leaving a flexible biconcave disc; birds, reptiles and fish keep oval, nucleated red cells throughout life.
Q 08What is the term for the proportion of blood volume occupied by red blood cells, normally about 45%?
Hematocrit
Hematocrit, also called packed cell volume, is read by spinning a sample in a centrifuge; values run higher in men than in women and rise at high altitude.
Q 09Platelets are not true cells but fragments of the cytoplasm of which large bone-marrow cells?
Megakaryocytes
Megakaryocytes, giant polyploid cells in the marrow, each shed thousands of platelets from their cytoplasm; the resulting anucleate fragments are unique to mammals.
Q 10Human blood pH is tightly regulated within which narrow range?
7.35 to 7.45
7.35 to 7.45 is the normal arterial range, held by bicarbonate buffering, with the lungs adjusting carbon dioxide and the kidneys excreting acid or base.
Q 11Approximately how many blood cells does human bone marrow produce every day?
500 billion
500 billion blood cells a day is the usual estimate, roughly 2 million red cells every second, released into the circulation through the marrow's permeable sinusoids.
Q 12Which Austrian physician discovered the ABO blood groups in 1901?
Karl Landsteiner
Karl Landsteiner, working in Vienna, sorted sera into groups he labelled A, B and C in 1901; the C was later renamed O, and AB was added in 1902.
Q 13The Rh blood factor was named after which animal, in whose red cells a similar antigen was found?
Rhesus macaque
Rhesus macaque red cells, injected into rabbits and guinea pigs in 1940, produced the antiserum that defined the factor; the human antigen later proved distinct, but the name stuck.
Q 21Haemophilia A is caused by low levels of which clotting factor?
VIII
VIII is the factor deficient in haemophilia A, the commoner form; haemophilia B involves factor IX, and both genes sit on the X chromosome, so males are mostly affected.
Q 22Iron-deficiency anaemia, the world's most common cause of anaemia, affects roughly how many people?
About one billion
About one billion people live with iron-deficiency anaemia, making it the commonest nutritional deficiency on Earth; folate and B12 shortages and thalassaemia are other causes.
Q 23Carriers of the sickle cell gene are partly protected against which disease?
Malaria
Malaria parasites fare worse in red cells carrying one sickle gene, a protective effect Anthony Allison demonstrated in 1954; the trait is commonest where malaria has been endemic.
Q 14Which blood type is known as the 'universal donor' for red cell transfusions?
O RhD-negative
O RhD-negative red cells carry neither A, B nor RhD antigens, so they can be given to almost anyone; hospitals reserve the supply for emergencies and O-negative patients.
Q 15Which blood type is called the 'universal recipient'?
AB RhD-positive
AB RhD-positive people carry A, B and RhD antigens on their red cells, so their serum holds no antibodies against any of them and accepts every ABO and Rh type.
Q 16Jean-Baptiste Denys, who performed the first animal-to-human transfusion in 1667, was physician to which king?
Louis XIV of France
Louis XIV of France employed Denys as a physician; Denys transfused lamb's blood into a feverish boy in June 1667, and after a later patient died the practice was banned in France.
Q 17James Blundell performed the first successful human-to-human blood transfusion in 1818 at which London hospital?
Guy's
Guy's was Blundell's hospital; he taught midwifery there and at St Thomas', and devised syringes and funnels to move blood straight from donor to patient.
Q 18In which city did Bernard Fantus set up the first US hospital blood bank in 1937?
Chicago
Chicago's Cook County Hospital housed the bank; Fantus, its director of therapeutics, coined the term 'blood bank' for a store of refrigerated donor blood.
Q 19Which physician described the circulation of the blood in his 1628 treatise De Motu Cordis?
William Harvey
William Harvey, physician to James I and Charles I, published De Motu Cordis in Frankfurt in 1628, showing that the heart pumps blood around a closed circuit.
Q 20Haemophilia is 'the royal disease' because which monarch passed the mutation to royal families across Europe?
Queen Victoria
Queen Victoria carried the mutation: her son Leopold had haemophilia, and through daughters Alice and Beatrice it reached the royal houses of Russia, Spain and Germany, including Tsarevich Alexei.
Q 24Leukemia is a cancer of which type of blood cell?
White cells
White cells, or leukocytes, multiply abnormally in leukemia; a healthy microlitre of blood carries between four and eleven thousand of them, far fewer than the millions of red cells.
Q 25Horseshoe crab blood is bright blue because it carries oxygen with which copper-based protein?
Hemocyanin
Hemocyanin carries oxygen using copper atoms, turning blue when oxygenated; horseshoe crab blood is also harvested for Limulus amebocyte lysate, a clotting agent that detects bacterial endotoxins.
Q 26Skinks of the genus Prasinohaema have green blood because of a build-up of which waste pigment?
Biliverdin
Biliverdin, a green bile pigment from haem breakdown, reaches such concentrations in these New Guinea lizards that their blood, muscles, bones and tongues are all green.
Q 27Vampire bats, the only mammals that feed solely on blood, are found on which continent?
The Americas
The Americas, from Mexico to Argentina, are home to all three vampire bat species, each in its own genus; an anticoagulant in their saliva keeps the wound flowing.
Q 28The medicinal leech secretes which peptide to stop its host's blood clotting while it feeds?
Hirudin
Hirudin, a 65-amino-acid peptide from the leech's salivary glands, binds thrombin directly; Hirudo medicinalis attaches with a sucker and can take several times its weight in blood.
Q 29The red-and-white barber's pole is a relic of which medical practice once performed by barber-surgeons?
Bloodletting
Bloodletting was a barber-surgeon's trade: the pole's red recalls blood and the white the bandages, and the practice rested on the ancient idea of balancing the humours.
Q 30Which US president asked to be bled heavily after a throat infection, shortly before his death in 1799?
George Washington
George Washington was bled repeatedly on 14 December 1799, losing an estimated 40 per cent of his blood in a day; he died that evening at Mount Vernon, aged 67.