Membranes â¢ Provide barrier function â Extracellular â Organelles â¢ Barrier can be overcome by âtransport proteinsâ â To mediate transmembrane movements of ions, Na + , K + â Nutrients, glucose, amino acids etc. â Water (aquaporins).
Boron is a chemical element with symbol B and atomic number 5. Produced entirely by cosmic ray spallation and supernovae and not by stellar nucleosynthesis, it is a low-abundance element in the Solar system and in the Earth's crust.
Therefore, if the question tells us that the average mass of a Boron atom is 10.81 amu (atomic mass units), then this means that in a large number of Boron atoms, all with have 5 protons, and some will have 5, and some will have 6 neutrons, yielding individual atoms with 10 amu and 11 amu.