Question

Assume a molecule must cross the cell membrane into a cell. The molecule is a very large protein. How will it be transported into the cell? 1) Active transport 2) Facilitated diffusion 3) Simple diffusion 4) Endocytosis

Answer 1

Very large molecules such as large proteins are transported into cells through a process called endocytosis, which is an active transport method requiring energy. Hence option 4 is CORRECT.

Step-by-step explanation:

When a very large molecule, such as a large protein, needs to cross the cell membrane into a cell, it typically cannot use simple diffusion, facilitated diffusion, or active transport due to the size and nature of the molecule. Instead, such molecules are transported into the cell by a mechanism known as endocytosis. Endocytosis is a form of vesicle transport, which involves the cell membrane engulfing the molecule to form a vesicle inside the cell. This process requires energy, often in the form of ATP, making it an active transport method.

Facilitated diffusion is a passive transport method where molecules move down a concentration gradient through specific protein channels in the membrane without the need for cellular energy. Transport proteins involved in this process, such as glucose transporters, aid in the movement of substances like glucose across the cell membrane. However, for very large molecules like large proteins, facilitated diffusion is not an option, leaving endocytosis as the viable transport mechanism.Hence option 4 is CORRECT.