Which motion of particles across a membrane requires energy? A. From high concentration to low concentration B. From low concentration to high concentration C. With no concentration gradient D. Through dynamic equilibrium
The Correct Answer and Explanation is :
The correct answer is B. From low concentration to high concentration.
Explanation:
The movement of particles across a membrane can occur through various processes, including passive and active transport.
- Passive Transport: This type of transport does not require energy. It occurs when particles move from an area of high concentration to an area of low concentration, following their concentration gradient. Examples of passive transport include diffusion and osmosis. In these processes, substances naturally move to achieve equilibrium, where concentrations are equal on both sides of the membrane.
- Active Transport: Unlike passive transport, active transport requires energy, typically in the form of ATP (adenosine triphosphate). This process occurs when particles move against their concentration gradient, from low concentration to high concentration. Active transport is essential for maintaining the proper concentrations of ions and molecules within cells, which is crucial for various cellular functions.
- Concentration Gradient: The concentration gradient is the difference in concentration of a substance between two areas. When particles move from low to high concentration, they are going against the gradient, which necessitates the use of energy. For example, cells often need to transport ions such as sodium and potassium to maintain cellular functions and electrical gradients. This is accomplished through active transport mechanisms like the sodium-potassium pump, which moves sodium ions out of the cell and potassium ions into the cell, both against their concentration gradients.
- Dynamic Equilibrium: This state occurs when the concentrations of particles are equal on both sides of the membrane, resulting in no net movement of particles. In this case, energy is not required, as the system is balanced.
In summary, movement from low concentration to high concentration is the only process listed that requires energy input, as it goes against the natural flow of particles.