Introduction:
Ribosomes are important organelles present in all living cells. These are responsible for protein synthesis, which is an essential biochemical reaction in living systems.

Answer:
The important biochemical reaction in living systems that is catalyzed by a ribosome is the formation of peptide bond.

Formation of Peptide Bond:
Peptide bond formation is a crucial step in the translation process, which involves the conversion of genetic information from a nucleotide sequence to a protein sequence. Ribosomes are responsible for the formation of peptide bonds between amino acids, which are the building blocks of proteins.

How Ribosome Catalyzes the Formation of Peptide Bond:
During translation, ribosomes move along the mRNA strand and read the codons, which are groups of three nucleotides that code for a particular amino acid. The ribosome then aligns the correct tRNA molecule, which carries the corresponding amino acid, to the codon on the mRNA. The ribosome then catalyzes the formation of a peptide bond between the amino acid carried by the tRNA and the growing polypeptide chain.

Significance of Ribosome in Living Systems:
Ribosomes are essential for protein synthesis, which is necessary for the growth, development, and maintenance of living systems. Proteins are involved in numerous biological processes, including enzymatic reactions, structural support, transport, and signaling.

Conclusion:
In conclusion, ribosomes are responsible for the formation of peptide bonds, which is an essential step in protein synthesis. Proteins are essential molecules in living systems and are involved in numerous biological processes. Ribosomes play a crucial role in the growth, development, and maintenance of living systems.