Final answer:
The nucleolus is responsible for assembling ribosomes, and the endoplasmic reticulum (ER) transports the proteins they make. Ribosomal RNA and proteins are assembled into ribosomal subunits in the nucleolus, then transported to the cytoplasm for protein synthesis. Proteins are the transported materials made by ribosomes on the ER, and the RNA components of ribosomes are synthesized in the nucleolus.
Step-by-step explanation:
The nucleolus, found within the nucleus, is primarily responsible for the assembly of ribosomes, which are manufactured from ribosomal RNA (rRNA) and proteins. Once assembled in the nucleolus, ribosomal subunits are then transported out of the nucleus to the cytoplasm where they engage in protein synthesis. The endoplasmic reticulum (ER), specifically the rough ER, is studded with ribosomes that synthesize proteins. As ribosomes make proteins, these proteins are transported through the ER, acting like an intracellular highway. The ER is also the site where lipids are produced and where proteins undergo modifications such as folding or the addition of sugars.
Regarding the question, 'The nucleolus x(ER) transports materials such as _________________ made by ribosomes.', the correct answer is A) Proteins. The ER is involved in the synthesis and transport of proteins and lipids, but the transport of materials it's being asked about specifically refers to the role of ER in protein transportation, following their synthesis by ribosomes.
Concerning where the RNA components of ribosomes are synthesized, the answer is D) nucleolus. This is the region within the nucleus dedicated to manufacturing the RNA essential for ribosome construction, after which ribosomal subunits exit through the nuclear pores into the cytoplasm, thereby facilitating protein synthesis.