IB Biology 7.3 Translation Notes

Introduction

Translation is the process by which a sequence of nucleotides in messenger RNA (mRNA) is decoded to produce a specific sequence of amino acids, forming a polypeptide chain. This essential biological process occurs in the cytoplasm of cells at ribosomes, which are complex molecular machines made of proteins and ribosomal RNA (rRNA). Translation is divided into three main stages: initiation, elongation, and termination. This study note will delve into each stage in detail, as well as the roles of the key molecules involved, such as mRNA, transfer RNA (tRNA), and ribosomes.

Components Involved in Translation

Messenger RNA (mRNA)

• Structure: mRNA is a single-stranded, linear RNA molecule.
• Function: It carries genetic information from DNA in the nucleus to the cytoplasm, where it serves as a template for protein synthesis.

Ribosomes

• Structure: Ribosomes consist of two subunits, one large and one small. Each subunit is made of rRNA and proteins.
• Function: They facilitate the binding of mRNA and tRNA and catalyze the formation of peptide bonds between amino acids.

Transfer RNA (tRNA)

• Structure: tRNA is a single-stranded RNA molecule that folds into a cloverleaf shape, stabilized by hydrogen bonds. It is about 80 nucleotides long.
• Function: tRNA molecules carry specific amino acids to the ribosome and match their anticodon with the mRNA codon.

Stages of Translation

Initiation

• Assembly of Components: The small ribosomal subunit binds to the mRNA at the start codon (AUG). The initiator tRNA carrying methionine binds to the start codon through complementary base pairing with its anticodon.