Which of the following organelles is not bound by a membrane?
Correct answer: A. Ribosomes
- A. Ribosomes
- B. Endoplasmic Reticulum (ER)
- C. Mitochondria
- D. Nucleus
Explanation
Ribosomes are the only organelles listed that do not have a membrane surrounding them; they are made up of ribosomal RNA and proteins, playing a vital role in translating mRNA into proteins. In contrast, the endoplasmic reticulum (ER), mitochondria, and nucleus are all membrane-bound organelles. The ER, consisting of rough and smooth regions, is essential for protein and lipid synthesis. Mitochondria, known for their double membranes, are responsible for energy production through ATP synthesis, while the nucleus, also double membrane-bound, contains the genetic material and coordinates cellular activities. Therefore, ribosomes stand out as the correct answer.
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About Cell Structure and Function
Animal, plant, prokaryotic and eukaryotic cells are compared through their membranes, cell walls, nuclei and cytoplasmic organelles. The work includes the structures and functions of mitochondria, chloroplasts, ribosomes, endoplasmic reticulum, Golgi apparatus and lysosomes, as well as chromosome organization and the distinction between chromatin and chromosomes.
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