16.7: A Brief Summary of Membrane Surface Functions
- Page ID
- 89258
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As the ultimate barrier and interface between the cell and its environment, the plasma membrane has a number of easily defined functions. Here are some, in anticipation of the next chapter:
- Cell-cell recognition leading to cell junctions and tissue formation.
- Communication by selective ion channels and energy-dependent ion pumps.
- Facilitated diffusion of molecules (e.g., glucose) that cannot otherwise diffuse intro or out of cells.
- Recognition of extracellular signaling molecules in the environment or even on other cells leading to the transduction of chemical information from outside to inside the cell.
- Participation in the immune recognition of humoral (blood- or lymph-borne) or cellular components of the immune system.
The localization in 2020 of a fluorescent-tagged RNA known to regulate genes to the extracellular surface of human cells was quite a surprise! This RNA was dubbed Membrane-AssociatedeXtracellular, or maxRNA. Check out maxRNAs at cell surfaces, or Human Nuclear RNA found at extracellular surface-full paper (Huang et al.) for some details. Discuss ways that maxRNAs could bind to a plasma membrane, how they might get to the extracellular surface, and how they would stay there? Also, hypothesize some functions of maxRNAs and how they might work?