In glycolysis and the krebs cycle, electrons are removed from glucose and taken up by molecules like nad+. in such a reaction, glucose is being and nad+ is being

Glucose is being oxidized and nad⁺ id being reduced.

Explanation:

When an electron is released from an element that element become oxidized so oxidation means the removal of electrons and when an electron is taken by an element it gets reduced. So reduction means gaining of electrons.

Therefore in the case of glycolysis and Kreb cycle, glucose is oxidized to CO₂ and H₂O by removing electrons and nad⁺ is reduced to NADH by accepting an electron from glucose.

The process of oxidation of glucose to CO₂ and H₂O is called respiration which releases energy in the cell and this energy is used to produce ATP which acts as a cellular form of energy for the cell.