Question

what stabilizes the phospholipid bilayer in a cell membrane? (this is another way of asking, why does a phospholipid bilayer exist?) select all that apply.
hydrophobic interactions among the tails on phospholipids
hydrogen bonding between hydrophilic heads on phospholipids and water molecules inside the cell.
hydrogen bonding between water molecules inside or outside the cell and polar or charged r - groups on proteins at the cell surface (either interior or exterior).
hydrogen bonding between hydrophilic heads on phospholipids and water molecules outside the cell.
hydrophobic interactions between the tails on phospholipids and nonpolar r - groups on membrane proteins.
why dont fats form lipid bilayers and thus the basic structure of the cell membrane, instead of phospholipids? choose the single best answer.
the hydrocarbon tails on fats are so long—and especially if the tails are saturated and thus straight—that they form strong hydrophobic interactions that stabilize fat as clumps or globules, not bilayers.
fats do not have polar or charged groups that can interact with water.
if the tails of lipids are long enough and straight enough—like waxes or butter—the hydrophobic interactions among lipids are strong enough to make them solid at room temperature.

Explanation:

1. Phospholipid bilayers are stabilized by hydrophobic interactions among the non - polar tails of phospholipids, which cluster together away from water. The hydrophilic heads of phospholipids interact with water molecules inside and outside the cell through hydrogen bonding. Interactions between phospholipid tails and non - polar R - groups on membrane proteins also contribute to stability. Hydrogen bonding between water and polar/charged R - groups on proteins at the cell surface is not directly related to phospholipid bilayer stability.
2. Fats do not form lipid bilayers because they lack polar or charged groups to interact with water. Phospholipids have a polar head group that can interact with water, allowing them to form bilayers with the non - polar tails in the interior. Fats, being non - polar throughout (except for the small glycerol part), do not have the necessary amphipathic nature for bilayer formation.

Answer:

1. Hydrophobic interactions among the tails on phospholipids

Hydrogen bonding between hydrophilic heads on phospholipids and water molecules inside the cell
Hydrogen bonding between hydrophilic heads on phospholipids and water molecules outside the cell
Hydrophobic interactions between the tails on phospholipids and nonpolar R - groups on membrane proteins

1. Fats do not have polar or charged groups that can interact with water.