Out here in the stroma, a bunch of different enzymes use the carbon dioxide molecules and hydrogen ions made during the light dependent phase to assemble sugar fragments which are half of a glucose molecule (just 3 carbon atoms, instead of the 6 required to make a complete glucose molecule).
An alkane, by definition, only has single bonds. Even if your second diagram made sense (it doesn't for the reason above) it would not be an alkane at all because there is a double bond. Alkanes are a functional group. It's called alkil. As a functional group they have the generic formula R(CH2)nH.
Functional groups are specific atoms, ions, or groups of atoms having consistent properties. A functional group makes up part of a larger molecule. For example, -OH, the hydroxyl group that characterizes alcohols, is an oxygen with a hydrogen attached. It could be found on any number of different molecules.Just as elements have distinctive properties, functional groups have characteristic chemistries.or example, -OH, the hydroxyl group that characterizes alcohols, is an oxygen with a hydrogen attached. It could be found on any number of different molecules. Just as elements have distinctive properties, functional groups have characteristic chemistries.