The capillaries of collenchyma tissue become thick due to the deposit of _____.
- A.Cellulose and Pectin
- B.Lignin and Cutin
- C.Pectin and Chitin
- D.Suberin and Cellulose
Correct answer
Explanation
The correct answer is A, Cellulose and Pectin. Collenchyma cells lay down extra cellulose and pectin at the corners of their walls, which makes the tissue strong and yet flexible.
Collenchyma is a simple permanent tissue of plants, found just under the epidermis in the stems and leaf stalks of dicot plants and in the midrib of a leaf. Its cells are living and elongated, thickened unevenly at the corners, with almost no space between them. This uneven thickening lets a young shoot or a leaf stalk bend in the wind without breaking, and it is what allows climbing stems to twist.
Option B is wrong because lignin thickens sclerenchyma and cutin waterproofs the epidermis. Option C is wrong because chitin is found in fungal walls and insect skeletons, not in plant tissue. Option D is wrong because suberin is deposited in cork cells.
Exam tip: parenchyma has thin cellulose walls, collenchyma adds cellulose and pectin at the corners and stays flexible, sclerenchyma is lignified, dead and rigid.
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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