1. Cell biology is a relatively new field of biology that came about as three fi
ID: 145017 • Letter: 1
Question
1. Cell biology is a relatively new field of biology that came about as three fields of biology merged to contribute knowledge and skills. What three fields of biology came together and what did each field contribute to the science of cell biology? Be specific in your descriptions. CHAPTER 2 2. Explain how and why a phospholipid bilayer spontaneously forms. What conditions need to be met? 3. Biological membranes are composed of many phospholipid molecules, which are amphipathic in nature. What is an amphipathic molecule, and why are they so important to both establishing and maintaining membranes? Why are biological membranes bilayers instead of monolayers and what does this have to do with the amphipathic nature of the phospholipids?Explanation / Answer
Answer 1) 3 fielda that contribute to science of cell biology are:
Answer 2 & 3) Phospholipid molecules cause them to form bilayers spontaneously in aqueous environments. Hydrophilic molecules dissolve readily in water because they contain charged groups or uncharged polar groups that can form either favorable electrostatic interactions or hydrogen bonds with water molecules. Hydrophobic molecules are insoluble in water because all, or almost all, of their atoms are uncharged and nonpolar and therefore cannot form energetically favorable interactions with water molecules. If dispersed in water, they force the adjacent water molecules to reorganize into icelike cages that surround the hydrophobic molecule. Because these cage structures are more ordered than the surrounding water, their formation increases the free energy. This free energy cost is minimized, however, if the hydrophobic molecules (or the hydrophobic portions of amphipathic molecules) cluster together so that the smallest number of water molecules is affected.
For this reason, lipid molecules spontaneously aggregate to bury their hydrophobic tails in the interior and expose their hydrophilic heads to water. Depending on their shape, they can do this in either of two ways: they can form spherical micelles, with the tails inward, or they can form bimolecular sheets, or bilayers, with the hydrophobic tails sandwiched between the hydrophilic head groups.
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