Problem 4 - Anatomy and Physiology of Animals

Question

Watch this video (http://openstaxcollege.org// ribosome) to learn about ribosomes. The ribosome binds to the mRNA molecule to start translation of its code into a protein. What happens to the small and large ribosomal subunits at the end of translation?

Step-by-Step Solution

Answer

The ribosomal subunits disassemble and separate after translation ends.

Step 1: Introduction to Ribosome and Translation

Translation is the process where ribosomes synthesize proteins by decoding mRNA. The ribosome is composed of a small and a large subunit that work together during this process.

Step 2: Ribosome Binding and Translation

At the start of translation, the small ribosomal subunit binds to the mRNA. The large subunit then joins to form the complete ribosome, enabling protein synthesis.

Step 3: Completion of Protein Synthesis

During translation, tRNAs bring amino acids to the ribosome, where they are assembled into a polypeptide chain according to the sequence of the mRNA. This process continues until a stop codon is reached on the mRNA.

Step 4: Disassembly of Ribosomal Subunits

Once a stop codon is reached, the translation process ends. The ribosome releases the newly synthesized protein and the mRNA. The large and small ribosomal subunits then dissociate and separate from each other.

Key Concepts

mRNA

Messenger RNA, or mRNA, plays a vital role in the creation of proteins. It carries genetic information from the DNA in the nucleus to the cytoplasm, where proteins are synthesized. This molecule is a single-stranded copy of a specific gene, containing the instructions needed to build a protein.
To understand mRNA's function, think of it as a blueprint for construction. Just like builders refer to blueprints to construct buildings, cells use mRNA to guide the assembly of proteins.

• mRNA is read in sequences of three nucleotides, known as codons.
• Each codon corresponds to a specific amino acid or serves as a start/stop signal in protein synthesis.

This coded message is what ribosomes translate into a functional protein.

translation process

The translation process is a complex mechanism that turns the genetic information carried by mRNA into proteins. Proteins are key players in all cellular processes, making this process crucial to life.
Translation occurs in the cytoplasm and involves several key steps.

• Initiation: The small ribosomal subunit binds to the mRNA, followed by the joining of the large subunit. This forms a complete ribosome.
• Elongation: Transfer RNAs, or tRNAs, ferry amino acids to the ribosome, matched to the codons on mRNA.
• Termination: When a stop codon is reached, the assembly of the protein ceases, and the complete polypeptide is released.

During each step, the ribosome ensures that the correct amino acids are added in the correct sequence, which determines the structure and function of the resulting protein.

ribosomal subunits

Ribosomes consist of two subunits, a small and a large one, each playing a specialized role in protein synthesis.
These subunits are composed of ribosomal RNA (rRNA) and proteins, and they only come together during translation.
### The Small Subunit The small subunit is responsible for binding the mRNA transcript. It ensures the correct alignment of the mRNA so that the codons can be read properly.
### The Large Subunit The large subunit contributes to forming peptide bonds between amino acids, linking them into a long chain that will fold into a functioning protein.
### Post-Translation Once translation is complete and a stop codon is reached, the two subunits separate. This dissociation allows them to be recycled for future rounds of protein synthesis, highlighting the efficiency of cellular processes.