An electron carrier that is used in harvesting energy from glucose molecules in a series of gradual steps in the cytoplasm is

The correct answer is NAD+

Explanation:

Glycolysis is the process that occurs in almost all the cells. It occurs in the cytoplasm in both prokaryotes and eukaryotes. In glycolysis partial oxidation of glucose takes place step wise and one glucose molecule gets convert into 2 pyruvate.

The molecule that helps in the partial oxidation of glucose is NAD+. NAD+ is an electron carrier that harvest energy in a series of gradual step from glucose in the form of electrons and gets reduced into NADH.  

Then this NADH is used to feed electrons in the ETC during oxidative phosphorylation to make ATP and get regenerated into NAD+. So the correct answer is NAD+.

thinking it would be physical characteristics

he forelimbs below belong to four species that descended in a direct line from the ancestral mammal shown above. of the four descendants shown, which species most likely appeared earliest in evolutionary history?