Transport Through the Cell Membrane
Type of Transport Requires Name of
Transport Protein Used Energy Transp-
Input from ort
Cell?
Simple
Diffusion
Facilitated
Diffusion
Active
Transport
Type of Transport Requires Name of
Transport Protein Used Energy Transp-
Input from ort
Cell?
Simple Diffusion No No No
Facilitated Diffusion Yes No No
Active Transport Yes Yes Yes
To understand the concept of transport through the cell membrane, we need to first grasp the concept of the cell membrane itself. The cell membrane is a selectively permeable barrier that separates the cell's internal environment from the external environment. It controls the movement of molecules in and out of the cell, allowing necessary substances to enter and waste products to exit.
Now, let's break down the three types of transport through the cell membrane:
1. Simple Diffusion: In simple diffusion, molecules move from an area of higher concentration to an area of lower concentration. This movement occurs without the need for any transport protein or energy input from the cell. Small, non-polar molecules, such as oxygen and carbon dioxide, can passively diffuse through the cell membrane.
2. Facilitated Diffusion: Facilitated diffusion also involves the movement of molecules from an area of higher concentration to an area of lower concentration. However, unlike simple diffusion, it requires the assistance of specialized transport proteins embedded in the cell membrane. These proteins facilitate the transport of larger, charged, or polar molecules that are unable to freely pass through the lipid bilayer. Despite the involvement of transport proteins, facilitated diffusion still does not require any energy input from the cell.
3. Active Transport: Active transport is a process that enables the movement of molecules against the concentration gradient – from an area of lower concentration to an area of higher concentration. This movement requires the assistance of specific proteins known as pumps. Active transport involves the input of energy derived from ATP (adenosine triphosphate) produced by the cell. These pumps actively transport ions and molecules across the cell membrane, creating concentration gradients that are vital for many cellular processes to occur.
In summary, simple diffusion does not require any transport protein or energy input from the cell, while facilitated diffusion requires transport proteins but no energy input. Active transport, on the other hand, needs both specific transport proteins and energy input from the cell in the form of ATP.