In plant cells, RNA is present in
- A.cytoplasm only
- B.nuclei and cytoplasm only
- C.nuclei, cytoplasm, mitochondria, chloroplast and endoplasmic reticulum
- D.nuclei, cytoplasm, mitochondria, chloroplast and ribosomes
Correct answer
Explanation
The correct answer is D. In plant cells RNA is found in the nucleus, the cytoplasm, mitochondria, chloroplasts and ribosomes.
RNA is made in the nucleus, where DNA is copied into messenger, transfer and ribosomal RNA; the nucleolus in particular is rich in ribosomal RNA. These molecules then move into the cytoplasm to take part in making proteins. Ribosomes are themselves built of ribosomal RNA and protein, so they are among the richest stores of RNA in the cell. Mitochondria and chloroplasts are semi-autonomous organelles with their own DNA and their own small ribosomes, so they make their own RNA and some of their own proteins.
A is wrong because RNA is not limited to the cytoplasm; it is made in the nucleus. B is wrong because it leaves out mitochondria, chloroplasts and ribosomes. C is wrong because the endoplasmic reticulum is a membrane system that does not make RNA of its own; the RNA on the rough ER belongs to the ribosomes attached to it.
Exam tip: mitochondria and chloroplasts are semi-autonomous, with their own DNA, RNA and 70S ribosomes.
Practice Questions
View allCell wall is absent in which one of the following organisms ?
- A.Bacteria
- B.Diatom
- C.Mushroom
- D.Tapeworm
Show answer
The tapeworm is an animal, and animal cells have no cell wall, only a cell membrane. A rigid cell wall lies outside the cell membrane in plants, fungi, most bacteria and many protists, giving the cell shape and protection.
Read the full explanation →Methanol is toxic because
- A.methanol coagulates the protoplasm
- B.methanol gets oxidised to methanal in liver which coagulates the protoplasm
- C.methanol gets oxidised to acetic acid in liver which coagulates the protoplasm
- D.methanol gets oxidised to CO in liver which coagulates the protoplasm
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In the liver, methanol is oxidised to methanal (formaldehyde), which coagulates protoplasm and damages cells. Methanol, CH3OH, is the simplest alcohol and is sometimes mixed into illicit liquor.
Read the full explanation →In which one of the following types of connective tissues in animals does fat get stored?
- A.Adipocyte
- B.Chondrocyte
- C.Osteocyte
- D.Reticulocyte
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Adipocytes are the fat cells of adipose tissue, a loose connective tissue that stores fat in animals. Adipose tissue lies mainly beneath the skin and around organs such as the kidneys and heart.
Read the full explanation →Which one of the following agents does not contribute to propagation of plants through seed dispersal?
- A.Wind
- B.Fungus
- C.Animal
- D.Water
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Seeds are carried away from the parent plant by wind, water and animals, but fungi play no part in seed dispersal.
Read the full explanation →Which one of the following is essential for thyroid gland to make thyroxin?
- A.NaCl
- B.KCl
- C.Cholesterol
- D.Iodine
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Thyroxine is an iodine-containing hormone, so the thyroid gland cannot make it without iodine from the diet. The thyroid is a butterfly-shaped gland in the neck.
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