Which structure primarily prevents harmful chemicals from entering animal cells?

• A. Golgi apparatus
• B. Plasma membrane
• C. Nucleus
• D. Mitochondrion

Answer: (B)

Verified step by step guidance

1. Understand the function of each structure listed in the problem: The Golgi apparatus is involved in modifying, sorting, and packaging proteins and lipids for secretion or use within the cell. The nucleus stores genetic material and regulates gene expression. The mitochondrion is responsible for energy production through cellular respiration. The plasma membrane acts as a selective barrier, controlling the entry and exit of substances.
2. Recall the role of the plasma membrane: It is a phospholipid bilayer embedded with proteins that selectively allow certain molecules to pass while blocking others, thus preventing harmful chemicals from entering the cell.
3. Consider the concept of selective permeability: The plasma membrane's structure includes hydrophobic and hydrophilic regions, which help regulate the movement of substances based on their chemical properties.
4. Eliminate incorrect options: The Golgi apparatus, nucleus, and mitochondrion do not directly prevent harmful chemicals from entering the cell. Their functions are unrelated to forming a protective barrier.
5. Conclude that the plasma membrane is the correct structure: It primarily prevents harmful chemicals from entering animal cells by acting as a selective barrier and maintaining cellular homeostasis.