What are ribosomes primarily composed of?

Ribosomes are primarily composed of proteins and ribosomal RNA (rRNA). This is significant because ribosomes serve as the site of protein synthesis in the cell. The rRNA molecules play a structural and catalytic role, forming the core of the ribosome and facilitating the translation of messenger RNA (mRNA) into amino acid sequences, while the proteins help to stabilize the structure and perform various functions within the ribosome.

In contrast, the inclusion of DNA along with proteins in one of the options is not accurate, as ribosomes do not contain DNA; they rely on mRNA, which is transcribed from DNA, to guide protein synthesis. Additionally, lipids and carbohydrates are not integral components of ribosomes; lipids are primarily involved in forming cellular membranes, while carbohydrates serve various roles such as energy storage and structural function in cells but are not part of ribosomal structure. Thus, the combination of proteins and ribosomal RNA accurately describes the composition that allows ribosomes to fulfill their crucial role in the protein synthesis process.