Advanced Placement (AP) Biology Practice Exam

What do ribosomes synthesize using information from DNA?

1. Carbohydrates

2. Lipids

3. Nucleotides

4. Proteins

The correct answer is: Proteins

Ribosomes are cellular structures responsible for synthesizing proteins, which are essential for a wide variety of cellular functions. The process begins when messenger RNA (mRNA), which carries genetic information transcribed from DNA, binds to ribosomes. As the ribosome moves along the mRNA, it translates the sequence of nucleotides into a specific sequence of amino acids. This translation process involves transfer RNA (tRNA) molecules that bring amino acids to the ribosome, where they are linked together to form a polypeptide chain, ultimately folding into a functional protein. Proteins are crucial for numerous biological processes, including enzymatic reactions, structural roles in cells, transport functions, and signal transduction. The synthesis of proteins through ribosomes is the key step in expressing the genetic instructions encoded in DNA, highlighting the central dogma of molecular biology: DNA → RNA → Protein. In the context of the other choices, carbohydrates, lipids, and nucleotides are not synthesized by ribosomes. Instead, carbohydrates are synthesized through processes like photosynthesis and cellular respiration, lipids are formed through the activity of various enzymes, and nucleotides are the building blocks of nucleic acids, synthesized by different pathways. Therefore, the synthesis of proteins is