Which of the following is true of GPL? Pick all that apply.
1) It has a fatty acid residue bonded to a glycerol via an ester linkage.
2) It has a fatty acid residue bonded to a glycerol via a phosphoester linkage.
3) It may contain a positively charged component.
4) It is an overall polar molecule, and is soluble in water.
5) Phosphatidic acid is an example of this.
6) It does not always have to contain a phosphate group.