Which one of the following organelles of mammalian cell is rich in hydrolytic enzymes ?
- A.Mitochondria
- B.Ribosomes
- C.Lysosome
- D.Nucleus
Correct answer
Explanation
The correct answer is C, Lysosome. Lysosomes are small membrane-bound sacs full of hydrolytic enzymes that digest worn-out parts and foreign material inside the cell.
Lysosomes are formed from the Golgi apparatus and were discovered by Christian de Duve. Their enzymes, such as lipases, proteases, nucleases and carbohydrases, work best in an acidic medium and can break down almost every kind of large molecule. They destroy bacteria taken in by white blood cells and remove old organelles. When a cell is badly damaged, the lysosomes may burst and digest the cell itself, which is why they are called the suicide bags of the cell.
A is wrong: mitochondria carry out cellular respiration and make ATP; they are the powerhouse of the cell. B is wrong: ribosomes are the sites of protein synthesis and have no membrane. D is wrong: the nucleus holds the DNA and controls the activities of the cell.
Exam tip: Lysosome, hydrolytic enzymes, suicide bag; mitochondria, ATP, powerhouse; ribosome, protein factory.
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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