Which of the following organelles is primarily responsible for the synthesis of proteins within a eukaryotic cell?
Mitochondria
Ribosomes
Golgi apparatus
Lysosomes
Correct Answer:B
Explanation
Correct Option: B. Ribosomes
Detailed Explanation:
Understanding Protein Synthesis:
Proteins are essential macromolecules that perform a vast array of functions within living organisms, including structural roles, enzymatic activities, and signaling. The process of synthesizing proteins is known as translation, which occurs in the cytoplasm of eukaryotic cells.
Role of Ribosomes:
Ribosomes are the primary organelles responsible for protein synthesis. They are composed of ribosomal RNA (rRNA) and proteins, forming two subunits (large and small). Ribosomes can be found either floating freely in the cytoplasm or attached to the endoplasmic reticulum (ER), forming what is known as rough ER.
During translation, ribosomes read the messenger RNA (mRNA) sequence, which is transcribed from DNA. The ribosome facilitates the binding of transfer RNA (tRNA) molecules that carry specific amino acids. As the ribosome moves along the mRNA, it catalyzes the formation of peptide bonds between the amino acids, ultimately forming a polypeptide chain that folds into a functional protein.
Why Other Options Are Incorrect:
A. Mitochondria:
Mitochondria are known as the "powerhouses" of the cell because they generate adenosine triphosphate (ATP) through cellular respiration. While they do have their own ribosomes and can synthesize some proteins (specifically those needed for mitochondrial function), they are not the primary site for protein synthesis in the cell.
C. Golgi Apparatus:
The Golgi apparatus is involved in modifying, sorting, and packaging proteins and lipids for secretion or delivery to other organelles. It does not synthesize proteins; rather, it processes proteins that have already been synthesized by ribosomes.
D. Lysosomes:
Lysosomes are membrane-bound organelles that contain digestive enzymes. Their primary function is to break down waste materials and cellular debris. They do not play a role in protein synthesis.
Summary of Key Points:
Ribosomes are the main organelles responsible for protein synthesis in eukaryotic cells.
They translate mRNA into polypeptide chains by facilitating the binding of tRNA and catalyzing peptide bond formation.
Other organelles like mitochondria, Golgi apparatus, and lysosomes have distinct functions unrelated to the synthesis of proteins.
Revision Summary:
Ribosomes are essential for protein synthesis in eukaryotic cells.
They read mRNA and assemble amino acids into proteins.
Mitochondria, Golgi apparatus, and lysosomes have different roles in the cell.
Understanding the function of each organelle is crucial for grasping cellular processes.