Which of the following options is NOT true of RBCs?
- A.Size - 7.5 μm
- B.Function - Transportation of oxygen and carbon dioxide
- C.RBCs count can be determined by an instrument called haemocytometer
- D.Shape - Amoeboid or circular
Correct answer
Explanation
The correct answer is D, Shape - Amoeboid or circular. A red blood cell is a biconcave disc, thin in the middle and thick at the edge, not an amoeboid cell. This shape gives it more surface area to pick up oxygen and lets it bend through narrow capillaries. Mature human RBCs have no nucleus, are about 7.5 micrometres wide, live for about 120 days and are made in the red bone marrow. Their red colour comes from haemoglobin, which carries oxygen from the lungs to the tissues and part of the carbon dioxide back. A is wrong as a choice because 7.5 μm really is the size of an RBC. B is wrong because carrying oxygen and carbon dioxide is exactly what RBCs do. C is wrong because a haemocytometer is indeed the counting chamber used to count blood cells under a microscope. Exam tip: RBC = biconcave, no nucleus, 120 days; WBC = amoeboid, has a nucleus; the amoeboid shape belongs to white cells, not red.
Practice Questions
View allThe fact that the planets move around the Sun, not in circles but in ellipses, was first demonstrated by
- A.Galileo
- B.Martin Luther
- C.Johannes Kepler
- D.Copernicus
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In 1609 Kepler showed that the planets move around the Sun in elliptical orbits, with the Sun at one focus of the ellipse.
Read the full explanation →Which one of the following statements is correct?
- A.Urea is produced in liver.
- B.Urea is produced in blood.
- C.Urea is produced from digestion of starch.
- D.Urea is produced in lung and kidney.
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Liver cells turn the toxic ammonia released from the breakdown of amino acids into urea through the ornithine cycle, also called the urea cycle.
Read the full explanation →Which one of the following is the correct sequence of passage of light in a compound microscope?
- A.Condenser-Objective lens-Eyepiece-Body tube
- B.Objective lens-Condenser-Body tube-Eyepiece
- C.Condenser-Objective lens-Body tube-Eyepiece
- D.Eyepiece-Objective lens-Body tube-Mirror
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Light passes through the condenser to the specimen, is picked up by the objective lens, travels up the body tube and reaches the eye through the eyepiece.
Read the full explanation →Which one of the following statements regarding haemoglobin is correct?
- A.Haemoglobin present in RBC can carry only oxygen but not carbon dioxide.
- B.Haemoglobin of RBC can carry both oxygen and carbon dioxide.
- C.Haemoglobin of RBC can carry only carbon dioxide.
- D.Haemoglobin is only used for blood clotting and not for carrying gases.
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It binds oxygen at its iron-containing haem groups and carries some carbon dioxide on its protein chains. Each haemoglobin molecule has four polypeptide chains and four haem groups, and each haem iron can hold one oxygen molecule, forming oxyhaemoglobin in the lungs.
Read the full explanation →Which one of the following statements regarding histone proteins is correct?
- A.Histones are proteins that are present in mitochondrial membrane.
- B.Histones are proteins that are present in nucleus in association with DNA.
- C.Histones are proteins associated with lipids in the cytosol.
- D.Histones are proteins associated with carbohydrates in the cytosol.
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They are the proteins around which DNA winds to form chromatin in the nucleus of eukaryotic cells. Histones are small basic proteins, rich in the positively charged amino acids lysine and arginine, which attract the negatively charged phosphate groups of DNA.
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