How do you identify the asymmetrical carbons in glucose and fructose? What do you need to look for in order to identify an asymmetric carbon?

A carbon bound to four different groups.
In sugars, most carbons that bear a hydroxyl will be chiral (asymmetric) carbons, because they are each bound to a hydroxyl, a hydrogen, and the rest of the carbon chain in two directions.
Four different groups means a chiral carbon.
Glucose
One form of glucose is the aldehyde form, shown below.
There is no internal mirror plane, so every carbon is different.
We see that carbon atoms ##2## through ##5## are chiral.
If two carbons are tied in deciding chirality, we look at the atoms next further out from them until we find a difference.
Each carbon is attached to four different groups.
In the list below, the atom that distinguishes the groups is shown in red.
##bb”C2″##: ##”H, OH, CH”color(red)(“O”)##, and ##”CH(“color(red)(“O”)”H)”##
##bb”C3″##: ##”H, OH”, “CH(OH)CH”color(red)(“O”)##, and ##”CH(OH)CH(OH)”color(red)(“C”)”##
##bb”C4″##: ##”H, OH, CH(OH)CH(“color(red)(“O”)”H)”##, and ##”CH(OH)CH”_2color(red)(“O”)”H”##
##bb”C5″##: ##”H, OH, CH(OH)”color(red)(“C”)## and ##”CH”_2color(red)(“O”)”H”##
Fructose
One form of fructose is the ketone form shown below.
We see that carbons ##3##, ##4##, and ##5## are chiral.
Each carbon is attached to four different groups as follows:
##bb”C3″##: ##”H, OH”, “C”color(red)(“=O”)##, and ##”CH(OH)”color(red)(“C”)##
##bb”C4″##: ##”H, OH, CH(OH)(C=O)”color(red)(“C”)##, and ##”CH(OH)CH”_2color(red)(“O”)”H”##
##bb”C5″##: ##”H, OH”, “CH(OH)”color(red)(“C”)## and ##”CH”_2color(red)(“O”)”H”##