Question

The small subunit of a ribosome is composed of a. a protein. b. an rRNA molecule. c. many proteins. d. many rRNA molecules. e. many proteins and one rRNA molecule.

Short answer

The correct answer is (e) many proteins and one rRNA molecule.

Step-by-step solution

Understanding the Basics of a Ribosome's Composition

Ribosomes are molecular machines that manufacture proteins inside cells. According to our biology knowledge, we know that they are composed of both proteins and rRNA molecules.

Identifying the Components of a Ribosome's Small Subunit

A small subunit of a ribosome includes both proteins and rRNA molecules.

Comparing the Options with the Identified Components

By comparing our findings from the previous step, we can eliminate options a, b, c, and d, as they mention only one component. The correct answer is therefore e, which states that the small subunit of a ribosome is composed of many proteins and one rRNA molecule.

Key concepts

Small Subunit of a Ribosome

The small subunit is an essential part of the ribosome, acting as a platform for protein synthesis. It is one of the two main subunits that form a ribosome. Unlike the large subunit, which assists in linking amino acids together, the small subunit plays a critical role in reading the mRNA (messenger RNA) blueprint for the protein.

The small subunit scans the mRNA, ensuring that the correct transfer RNA (tRNA) binds to the messenger RNA. This position and role are crucial for the fidelity and accuracy of protein synthesis. Thus, the small subunit acts as a guide and reader, orchestrating the translation process.

Role of rRNA in Ribosomes

Ribosomal RNA (rRNA) is a fundamental component of ribosomes. It works in conjunction with proteins to create the functional units of the ribosome. In the case of the small subunit, a single rRNA molecule is integral to its structure and function.

The rRNA in the small subunit helps to maintain its shape, allowing it to interact correctly with mRNA and tRNA during translation. It also aids in catalysis, ensuring that proteins are synthesized effectively and efficiently.

• Structural role: Holds the ribosomal proteins in the correct configuration.
• Functional role: Facilitates the binding of mRNA and tRNA.
Thus, rRNA is not just a structural element but a crucial player in ribosomal activity.

Protein Composition of the Small Subunit

The protein composition of the small subunit consists of numerous proteins. These proteins combine with rRNA to form a complex and dynamic structure. Although the exact protein count can vary among different organisms, the collaborative association between these proteins and rRNA is consistent.

These proteins play several roles, including:

• Assisting in the assembly of the small subunit.
• Stabilizing interactions between the rRNA and other molecules.
• Enhancing the efficiency of mRNA and tRNA binding.

The synergy between these proteins and rRNA allows the ribosome to function as a highly effective molecular machine.

Ribosomes as Molecular Machines

Ribosomes are often likened to molecular machines because they perform precise and essential functions in the cell. They translate genetic information from mRNA into proteins, which are key to virtually all cellular processes.

These "machines" are incredibly efficient, capable of assembling amino acids into proteins with remarkable accuracy and speed. The small subunit plays an integral role in this, acting like a cog in this sophisticated machine that ensures proteins are built according to the genetic instructions laid out in the mRNA.

• Operates with high precision, ensuring that cells have the proteins they need.
• Transforms genetic codes into functional proteins, essential for life.

Thus, ribosomes exemplify how biological systems operate like advanced machinery to sustain life.