Which of the following structures controls the activities of the living cell?

Step 1: Analyze the question The question asks which cell structure acts as the "control center" that directs the cell's activities (growth, metabolism, reproduction).

Step 2: Explain the concept Each organelle has a specific role:

• Nucleus: Contains the chromosomes (DNA), which carry genes. These genes hold the instructions for making proteins and enzymes. Since enzymes control all chemical reactions in the cell, the nucleus controls the cell's activities. It also controls cell division.
• Centrosome: Helps organize the spindle fibres during cell division in animal cells. It does not control the whole cell.
• Mitochondrion: The "powerhouse" of the cell. It releases energy (ATP) through aerobic respiration.
• Golgi body: Modifies, packages, and secretes substances such as proteins and enzymes. It is also involved in forming lysosomes.

Step 3: Work through the options

• A. Nucleus: directs and regulates all cell activities. ✔
• B. Centrosome: only assists in cell division. ✘
• C. Mitochondrion: supplies energy, not control. ✘
• D. Golgi body: packaging and secretion. ✘

Step 4: Answer The nucleus controls the activities of the living cell.

Exam tip: Link each organelle to a keyword:

• Nucleus → Control
• Mitochondrion → Energy
• Golgi body → Packaging/Secretion
• Ribosome → Protein synthesis
• Centrosome → Spindle formation

When you see "controls" or "directs" in a cell question, think nucleus first.