The Ribosome as a Molecular Machine
The ribosome is a large RNA-protein molecular machine that translates nucleotide information into ordered amino-acid sequences.
The Investigative Question
How does the ribosome coordinate information reading, molecular recognition, and protein synthesis?
What We Observe
Ribosomes move along messenger RNA while coordinating transfer RNAs carrying amino acids. The sequence of codons in the messenger RNA determines the sequence in which amino acids are incorporated into a growing protein.
Scientific Background
The ribosome contains ribosomal RNA and numerous proteins. Its functional centers coordinate messenger RNA, transfer RNAs, peptide-bond formation, movement along the message, and release of the completed protein.
Why It Matters
The ribosome connects the information system examined in Investigation #4 with the molecular machinery considered here. It is simultaneously an information-processing system and a physical molecular machine.
What Is Known
Ribosome structure and function are understood in considerable detail. Structural studies show that the catalytic center responsible for peptide-bond formation is dominated by ribosomal RNA.
What Is Proposed
Evolutionary models commonly propose that simpler RNA-based translation systems preceded the modern ribosome and gradually incorporated proteins and additional regulatory components.
What Remains Uncertain
The earliest stages of translation remain difficult to reconstruct because some form of translation was already present before the last universal common ancestor of modern cellular life.
Key Numbers
Bacterial ribosomes contain three major ribosomal RNAs and dozens of ribosomal proteins organized into two principal subunits.
Design Relevance
The ribosome is relevant to design because it demonstrates the close relationship between biological information and molecular machinery. The machine operates successfully only within a larger system that supplies encoded RNA, charged transfer RNAs, energy, and supporting factors.
Assessment
The ribosome should not be considered in isolation. Its function illustrates the integrated nature of biological systems in which information storage, decoding, molecular recognition, catalysis, and energy use cooperate.