The phospholipid bilayer forms the cell membrane, which acts as a selective barrier, controlling the entry and exit of molecules while maintaining the internal environment of the cell.
Passive transport involves the movement of molecules from high to low concentration without the need for energy (e.g., simple diffusion, facilitated diffusion).
Second messengers like cyclic AMP (cAMP) amplify the signal received by a receptor and help propagate it inside the cell, leading to specific cellular responses.
The proton gradient, established by the electron transport chain across the inner mitochondrial membrane, drives ATP synthesis through ATP synthase.
Active transport moves molecules against their concentration gradient using energy from ATP, unlike osmosis, simple diffusion, or facilitated diffusion, which are energy-independent processes.
