What is the main driving force for massive production of ATP molecules in the mitochondria?

1 point proton gradient established from electron transport system

2 electrons obtained from the citric acid cycle

3 reduction of oxygen by glycolysis

4 transport of water via ATP synthase

What are major products from the citric acid cycle?

1 GTP, oxygen

2 NADH, carbon dioxide

3 water, NADH

4 ATP, oxygen