A greater degree of unsaturation results in a disruption of van der Waals forces between fatty acid chains. This is due to the "kinks" that occur within an unsaturated fatty acid. It is easy to visualize a fatty acid membrane with kinks being less tightly packed, and therefore more fluid. This increase in fluidity is independent of temperature.

The rules for fatty acid nomenclature state that Omega 6 means that a double bond is located at the sixth position of the fatty acid - counting from the methyl end.

Linoleic acid's nomenclature is C18:29,12. Linolenic acid's nomenclature is C18:39,12,15. They both have 18 carbons but differ by one extra double bond in linolenic acid. 

Glycerol phosphate can be created by the glycerol phosphate shuttle. Insects use this process in their muscles for flying, because they require quick ATP synthesis. To generate that ATP, the NADH synthesized during glycolysis ends up being regenerated into , and is shuttled over to the mitochondria to participate immediately in oxidative phosphorylation. Via the glycerol phosphate shuttle, NADH reduces dihydroxyacetone phosphate directly into glycerol phosphate, in a reaction that is catalyzed by glycerol 3-phosphate dehydrogenase. The metabolite here that can be recognized from glycolysis is the dihydroxyacetone phosphate. Phosphoenolpyruvate, pyruvate, and 3-phosphoglycerate are all indeed glycolysis metabolites, but none could be easily reduced to glycerol 3-phosphate. If you guessed glyceraldehyde 3-phosphate, you’d be close, because structurally, it appears that it could also be directly reduced to glycerol phosphate. Indeed, during glycolysis, it is interconverted to dihydroxyacetone phosphate. But the glycerol phosphate shuttle uses dihydroxyacetone phosphate; hence, the answer is dihydroxyacetone phosphate.

Phospholipids are amphipathic, meaning they have an end that is hydrophobic (the fatty acid tail) and an end that is hydrophilic (the head). Phosphate groups have a negative charge, thus attracting them to water, and the presence of a phosphate group at the head of a phospholipid makes that head hydrophilic. Glycerol itself polarizes a fatty acid, but the glycerol is located in the head, not the backbone, and is not charged like phosphate.

The polar head groups and the hydrocarbon tails will separate themselves in such a way that one-tailed phospholipids will form micelles, whereas two-tailed phospholipids will form a bilayer (liposome). 

Phospholipids have two hydrocarbon tails, and one is indeed usually relatively saturated (has no double bonds) and the other relatively saturated (has double bonds). The degree of saturation, as well as the length, influences membrane fluidity; more cis-double bonds pack together less tightly, and decrease fluidity. In order to minimize free energy, the hydrophobic parts of phospholipids rearrange to refill a bilayer if it happens to break. In water, phospholipids can form a membrane, or a sphere called a micelle in which the hydrophobic tails pack together. Note that the tails are hydrophobic, and the heads are hydrophilic; tails are oriented toward the interior of a bilayered membrane.

Phospholipids and glycolipids have two hydrocarbon chains, whereas free fatty acids only have one.  The extra carbon tail, in combination with the unsaturation of these types of lipids (double bonds present) makes them far bulkier than free fatty acids.  The extra bulk disallows micelle formation, and bilayers (liposomes) form instead.

A typical phospholipid is made up of a glycerol with two fatty acid carbon chains stemming off of it. On the other side of the glycerol a phosphate group is connected, an ester group connects the tail to the head. An amino group, however, is not present.

Steroid hormones are derivatives of cholesterol and therefore can pass through the plasma membrane of cells since they are lipophilic. Steroid hormones generally don't bind on the surface of plasma membranes, but instead to receptors inside the cell itself. Since they are nonpolar, they are carried by proteins in the blood.