The difference between passive and active transport lies in the energy requirement for moving molecules across a membrane.
1. Passive transport: In passive transport, molecules move from an area of high concentration to an area of low concentration without the input of energy. This process occurs naturally due to the random movement of molecules, known as diffusion. Passive transport includes simple diffusion, facilitated diffusion, and osmosis.
2. Active transport: Active transport, on the other hand, requires the cell to expend energy to pump molecules against their concentration gradient, from an area of low concentration to an area of high concentration. This process is carried out by specific proteins in the cell membrane called pumps.
Now, regarding why different types of molecules like O2 and CO2 can diffuse in opposite directions across a membrane:
- Oxygen (O2) and Carbon Dioxide (CO2) are small, nonpolar molecules that can passively diffuse across the cell membrane through simple diffusion.
- O2 moves from an area of high concentration (outside the cell) to an area of low concentration (inside the cell) to meet cellular demands for respiration.
- CO2, produced as a waste product during cellular respiration, moves in the opposite direction, from inside the cell (high concentration) to outside (low concentration).
This bidirectional movement of O2 and CO2 showcases how molecules can diffuse in opposite directions based on their concentrations inside and outside the cell, highlighting the dynamic nature of passive transport in maintaining cellular functions.
