Which type of protein is embedded in the cell membrane in both active transport and facilitated transport?

Carrier proteins are integral membrane proteins that play a crucial role in both active transport and facilitated transport across the cell membrane. In facilitated transport, carrier proteins help move substances down their concentration gradient, allowing them to cross the membrane without the expenditure of energy. In active transport, these proteins undergo conformational changes to transport molecules against their concentration gradient, which often requires energy in the form of ATP.

The versatility of carrier proteins lies in their ability to bind specific substrates and facilitate their movement, whether it be with or against the gradient. This dual functionality makes them essential for cellular processes that require precise regulation of substance levels within the cell, such as the transport of glucose and ions.

In contrast, receptor proteins primarily serve to receive signals from outside the cell and do not participate in the transport of molecules. Channel proteins specifically create passageways for passive transport of ions and water but do not typically engage in the active transport process. Structural proteins, on the other hand, provide support and shape to the cell but are not involved in the transport functions essential for cellular metabolism.

Overall, carrier proteins are vital for transporting molecules in and out of cells, making them integral to both types of processes mentioned.