NAD+ is a limiting factor in glycolysis. In the absence of ____________________ the conversion of (1) ____________________ to NAD+ via the ______________________________ is prevented from happening. In eukaryotes, the hydrogen atoms of the molecules mentioned in (1) are transferred to certain organic molecules in one of two methods: (2) ___________________________________ as can occur in yeast and ___________________________________ as can occur in human cells. In the process mentioned in (2), the hydrogen atoms are passed to ____________________, which is then converted to a molecule of ethanol. During this a molecule of ____________________ is oxidized to a molecule of ____________________, which allows glycolysis to continue on.