The words which comes in the blanks are NADH and electron.
A molecule generated in both glycolysis and krebs cycle, called NADH , donates electrons to the first protein in the electron transport chain.
Kerbs cycle is also known as citric Acid cycle or tri-carboxylic acid cycle.
NADH, stands for nicotinamide adenine dinucleotide, and it is an important pyridine nucleotide.