Question

Need explanations

• From a name, describe a lipid’s composition.

• Explain the relationship between permeability of membranes and the solubility of small
molecules in nonpolar solvents.

Answer 1

a)Phospholipids

Structure of Phospholipids
Your cells are surrounded by a very important type of lipid, called phospholipids. Phospholipids consist of a hydrophilic (or 'water loving') head and a hydrophobic (or 'water fearing') tail. Phospholipids like to line up and arrange themselves into two parallel layers, called a phospholipid bilayer. This layer makes up your cell membranes and is critical to a cell's ability to function.

Composition of Phospholipids
Lipids all have one thing in common - they do not mix well with water. You can see this quite well if you try to combine oil and water. No matter how much or how hard you shake them together, they remain separated. This can be useful for organisms. For example, ducks produce lipids in their feathers, allowing the water to roll right off their backs and helping the ducks stay afloat.

Phospholipids are made up of two fatty acids (long chains of hydrogen and carbon molecules), which are attached to a glycerol 'head.' The glycerol molecule is also attached to a phosphate group, and this is the hydrophilic part of the molecule. The 'tail' ends of the fatty acid chains opposite the glycerol is the hydrophobic part of the molecule.

b) completely non polar molecules can pass through easily. Polar or charged molecule have to lose their shell of surrounding water molecules and diffuse through lipid.