Final Answer:
The cell membrane structure regulates the transport of substances in and out of a cell.
The correct option is A.
Step-by-step explanation:
The structure responsible for regulating the transport of substances in and out of a cell is the cell membrane, also known as the plasma membrane. It acts as a semi-permeable barrier, controlling the movement of molecules and ions to maintain cellular homeostasis and facilitate the exchange of essential substances.
The cell membrane, or plasma membrane, is the biological structure that plays a crucial role in regulating the transport of substances into and out of a cell. This membrane is often described as semi-permeable, meaning it selectively allows certain molecules or ions to pass through while restricting others. This selective permeability is essential for maintaining cellular homeostasis, as it controls the internal environment of the cell.
The cell membrane is primarily composed of a lipid bilayer embedded with proteins. The lipid bilayer provides a barrier that separates the internal and external environments of the cell. The proteins within the membrane serve various functions, including acting as channels, carriers, receptors, and enzymes involved in different aspects of cellular transport and signaling.
As substances move across the cell membrane, they may do so through passive processes like diffusion or facilitated diffusion, or through active processes like active transport. The regulation of these processes ensures that the cell receives necessary nutrients, expels waste products, and maintains an optimal internal environment for cellular activities.
So, the correct option is A.