The question asks to identify the organelle responsible for lipid synthesis. We need to recall the primary functions of each given organelle.
A) Smooth Endoplasmic Reticulum is the primary site for the synthesis of lipids, including phospholipids, cholesterol, and steroid hormones. It also plays a crucial role in detoxification and calcium storage.
The question asks about the primary function of the nucleolus. To answer this, recall the main roles of different cellular organelles, specifically focusing on the nucleolus and nucleic acid synthesis.
Correct Option: A) Ribosomal RNA (rRNA)
The nucleolus is famously known as the "ribosome factory" of the cell because it is the primary site for the transcription of ribosomal RNA (rRNA) and the assembly of ribosomal subunits. These subunits are crucial for protein synthesis in the cytoplasm.
The question asks to identify the largest organelle in a cell. To answer this, we need to recall the typical sizes and functions of the given organelles.
D) Nucleus is generally considered the largest organelle in a eukaryotic cell. It is the most conspicuous organelle and houses the cell's genetic material, controlling cell growth and reproduction.
The question asks about the function of nuclear pores in transporting substances across the nuclear envelope. Nuclear pores are essential for regulating the passage of molecules between the nucleus and the cytoplasm.
A) mRNA and ribosomal subunits out of the nucleus. This is correct because mRNA is transcribed in the nucleus and must exit to the cytoplasm for translation, and ribosomal subunits are assembled in the nucleolus (within the nucleus) and must exit to the cytoplasm to form functional ribosomes. Both processes rely on nuclear pores for transport.
The question asks which theory is supported by the fact that mitochondria have their own DNA. This requires understanding the key tenets of each theory listed and how the presence of mitochondrial DNA relates to them.
D) Endosymbiotic theory — The Endosymbiotic theory posits that mitochondria evolved from free-living prokaryotes that were engulfed by ancestral eukaryotic cells. The presence of their own circular DNA, similar to bacterial DNA, and their own ribosomes, along with their ability to self-replicate, are crucial pieces of evidence supporting this theory.
The question asks to identify the type of cells that lack a membrane-bound nucleus. This is a fundamental concept in cell biology, distinguishing between the two main categories of cells: prokaryotic and eukaryotic.
C) Prokaryotic cells
Prokaryotic cells, such as bacteria and archaea, are defined by the absence of a membrane-bound nucleus. Their genetic material is found in a region called the nucleoid, which is not enclosed by a membrane.