Transpo of two substances across the cell membrane in the same direction is known as?
**Core Concept**
The transport of two substances across the cell membrane in the same direction is a fundamental process that occurs in various cellular contexts. This phenomenon is crucial for maintaining cellular homeostasis, nutrient uptake, and waste removal. The process involves the movement of substances against or with their concentration gradient.
**Why the Correct Answer is Right**
The correct answer is facilitated diffusion. Facilitated diffusion is a type of passive transport that involves the movement of molecules or ions across the cell membrane with the help of carrier proteins or channel proteins. These proteins provide a pathway for substances to move down their concentration gradient, allowing for the simultaneous transport of two or more substances in the same direction. This process is essential for the uptake of essential nutrients, such as glucose and amino acids, and the removal of waste products.
**Why Each Wrong Option is Incorrect**
**Option A:** Active transport is incorrect because it involves the movement of substances against their concentration gradient, which requires energy input. Active transport is not limited to the transport of two substances in the same direction.
**Option B:** Osmosis is incorrect because it is a type of passive transport that involves the movement of water molecules across a selectively permeable membrane, not the transport of two substances in the same direction.
**Option C:** Endocytosis is incorrect because it is a type of active transport that involves the engulfment of substances by the cell membrane, forming vesicles that are then transported into the cell. Endocytosis is not limited to the transport of two substances in the same direction.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that facilitated diffusion is a passive process that relies on the concentration gradient of the substance, whereas active transport requires energy input to move substances against their concentration gradient.
**Correct Answer: C. Facilitated diffusion**