Which substance on the plasma membrane identify chemical signals from outside the cell?
question 19 options:

carbohydrate chain

cholesterol

membrane protein

transport protein

The correct answer is carbohydrate chain.

Explanation:

Plasma membrane contain various proteins such as peripheral proteins,transmembrane proteins,GPI anchored proteins.Among them some protein contain carbohydrate chain basically oligosaccharide chain which is arranged in the extracellular portion of the plasma membrane.

 The principle function of these oligosaccharide side chains is to detect various chemical and biochemical signals from outside the cell .

 For example integrin is a glycoprotein that detect the signal for communicating with the adjacent cells.

for  example, forests have higher evapotranspiration than other ecosystems,  such  as grasslands, because of their deeper roots and greater leaf area. thus forests have a net moistening effect on the atmosphere and become a moisture source for downwind ecosystems.

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