Explanation:
There are generally four main types of cell signaling in multicellular organisms:
- Paracrine signaling: signals act on nearby cells.
- Autocrine signaling: cells signal to themselves.
- Endocrine signaling: signals travel long distances through the bloodstream.
- Direct contact signaling (also called juxtacrine): cells communicate through direct membrane contact or gap junctions.
This classification is widely accepted in biology and supported by multiple sources.
Some sources mention additional types like intracrine signaling (signals act inside the same cell) and juxtacrine as a subtype of direct contact, bringing the total to about 5 or more depending on classification details. However, the most common answer to how many types there are is 4.
Hence, the correct choice is:
(A) 4.
Explanation by: Mr. Dubey
There are generally four main types of cell signaling in multicellular organisms:
- Paracrine signaling: signals act on nearby cells.
- Autocrine signaling: cells signal to themselves.
- Endocrine signaling: signals travel long distances through the bloodstream.
- Direct contact signaling (also called juxtacrine): cells communicate through direct membrane contact or gap junctions.
This classification is widely accepted in biology and supported by multiple sources.
Some sources mention additional types like intracrine signaling (signals act inside the same cell) and juxtacrine as a subtype of direct contact, bringing the total to about 5 or more depending on classification details. However, the most common answer to how many types there are is 4.
Hence, the correct choice is:
(A) 4.