Which one of the following organelles can be seen in a prokaryotic cell?
- A.Mitochondria
- B.Definitive nucleus
- C.Ribosomes
- D.Golgi bodies
Correct answer
Explanation
The correct answer is C, Ribosomes. Ribosomes are the only one of these found in prokaryotic cells such as bacteria, because they are not enclosed by a membrane.
Prokaryotic cells, found in bacteria and archaea, are small and simple. Their DNA lies in a region of the cytoplasm called the nucleoid, with no nuclear membrane around it, and they have no membrane-bound organelles. They do have a cell membrane, usually a cell wall, cytoplasm and ribosomes, which make proteins. Prokaryotic ribosomes are of the 70S type, smaller than the 80S ribosomes in the cytoplasm of eukaryotic cells. This difference is why some antibiotics, such as streptomycin, can block bacterial ribosomes without harming human cells.
Option A is wrong because mitochondria are membrane-bound organelles found only in eukaryotic cells. Option B is wrong because a true nucleus with a nuclear envelope is the very thing prokaryotes lack. Option D is wrong because Golgi bodies are membrane-bound organelles of eukaryotic cells.
Exam tip: prokaryote = no nuclear membrane, no membrane-bound organelles, 70S ribosomes; eukaryote = 80S.
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.
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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