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.
Thus the methyl group is methane minus one hydrogen, with the unspecified valency (hyphen or line) added. To name a group or substituent, simply delete the family suffix of an alkane (-ane) and replace it with the family name for a substituent or group (-yl).-H Bonds. The Simple Alkanes: The simplest alkane is methane, which contains one carbon atom. Its molecular formula is CH4. It has four equivalent C-H bonds, formed by the overlap of the four carbon sp3 hybrid orbitals with the 1s AO of four different hydrogen atoms.