OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

Where do chemical reactions mainly occur in a cell?

1. Nucleus

2. Ribosome

3. Cytoplasm

4. Mitochondria

The correct answer is: Cytoplasm

Chemical reactions in a cell predominantly occur in the cytoplasm, as it serves as the site for many metabolic processes. The cytoplasm contains enzymes that facilitate these reactions, allowing the cell to carry out essential functions like energy production, nutrient breakdown, and the synthesis of biomolecules. While the other areas of the cell have specific roles, they do not serve as the primary locations for the variety of chemical reactions that occur. The nucleus is primarily involved in storing genetic material and controlling cellular activities, the ribosomes are crucial for protein synthesis, and the mitochondria are primarily concerned with cellular respiration and energy production. However, even in the case of mitochondria, some of the preparatory reactions happen in the cytoplasm before they enter the mitochondria for further processing. Thus, the cytoplasm is a central hub for numerous biochemical interactions and pathways necessary for the cell's survival and function.