Red blood cells (RBCs) have
- A.no nucleus, no mitochondria and no endoplasmic reticulum
- B.nucleus, mitochondria and endoplasmic reticulum
- C.nucleus, mitochondria but no endoplasmic reticulum
- D.no mitochondria but endoplasmic reticulum is present
Correct answer
Explanation
The correct answer is A, no nucleus, no mitochondria and no endoplasmic reticulum. Mature human red blood cells lose these organelles as they develop.
Red blood cells are made in the red bone marrow and push out their nucleus and other organelles before entering the blood. This leaves more room for haemoglobin, the iron-containing pigment that carries oxygen, and gives the cell its flexible biconcave disc shape. Without mitochondria they get energy by anaerobic glycolysis, so they do not use up the oxygen they carry. They live about 120 days and are broken down in the spleen and liver.
B is wrong because mature human RBCs have none of the three structures.
C is wrong because they have neither a nucleus nor mitochondria.
D is wrong because the endoplasmic reticulum is also absent.
Exam tip: mammalian RBC = no nucleus, no mitochondria, biconcave, life about 120 days, made in bone marrow, destroyed in spleen (graveyard of RBCs).
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
Show answer
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.
Show answer
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
Show answer
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.
Show answer
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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