What structure controls the passage of substances in and out of the cell?

What structure controls the passage of substances in and out of the cell?

• A. Nucleus
• B. Cell membrane
• C. Ribosome
• D. Mitochondria

Answer: (B)

The structure that controls the passage of substances in and out of the cell is the cell membrane. The cell membrane, also known as the plasma membrane, is a selective barrier composed primarily of a phospholipid bilayer with embedded proteins. This organization allows it to regulate the movement of ions, nutrients, and waste products, maintaining the internal environment of the cell. Key functions of the cell membrane include active transport and passive transport mechanisms, such as diffusion and osmosis. Proteins in the membrane can act as channels or carriers to facilitate the movement of specific molecules, while the lipid bilayer itself acts as a barrier to prevent unwanted substances from entering the cell. Through these processes, the cell membrane plays a crucial role in cellular homeostasis. The nucleus primarily functions as the control center of the cell, housing genetic material and coordinating cellular activities, rather than controlling substance passage. Ribosomes are the sites of protein synthesis and do not have a role in the transport of substances across the membrane. Mitochondria are essential for energy production through cellular respiration, but they also do not regulate the passage of substances into and out of the cell.

The structure that controls the passage of substances in and out of the cell is the cell membrane. The cell membrane, also known as the plasma membrane, is a selective barrier composed primarily of a phospholipid bilayer with embedded proteins. This organization allows it to regulate the movement of ions, nutrients, and waste products, maintaining the internal environment of the cell.

Key functions of the cell membrane include active transport and passive transport mechanisms, such as diffusion and osmosis. Proteins in the membrane can act as channels or carriers to facilitate the movement of specific molecules, while the lipid bilayer itself acts as a barrier to prevent unwanted substances from entering the cell. Through these processes, the cell membrane plays a crucial role in cellular homeostasis.

The nucleus primarily functions as the control center of the cell, housing genetic material and coordinating cellular activities, rather than controlling substance passage. Ribosomes are the sites of protein synthesis and do not have a role in the transport of substances across the membrane. Mitochondria are essential for energy production through cellular respiration, but they also do not regulate the passage of substances into and out of the cell.