A Level Biology Practice Exam

What is the primary function of ribosomes?

1. Synthesizing DNA

2. Assembling amino acids into polypeptides

3. Transporting nutrients

4. Breaking down waste products

The correct answer is: Assembling amino acids into polypeptides

The primary function of ribosomes is to assemble amino acids into polypeptides, which are the building blocks of proteins. This process is known as translation, and it occurs when ribosomes read the messenger RNA (mRNA) sequence that has been transcribed from DNA. Each group of three nucleotides on the mRNA, known as a codon, corresponds to a specific amino acid. As the ribosome moves along the mRNA strand, it facilitates the binding of transfer RNA (tRNA) which carries the appropriate amino acids, allowing them to be linked together in the correct sequence to form a polypeptide chain. This polypeptide chain will ultimately fold into a specific three-dimensional shape, resulting in a functional protein that can perform various roles within the cell, such as acting as enzymes, structural components, or signaling molecules. The ability of ribosomes to synthesize proteins is fundamental to cellular function and metabolism, highlighting their essential role in the biological processes that sustain life.