Which process in respiration takes place last

            Electron transport chain is the last step of respiration.

Explanation:
                     Respiration is a cellular process in which glucose molecule is broken down into carbon dioxide, water and ATP is produced as end product. Respiration consists of following main steps:

1. Glycolysis:
                It occurs in the cytoplasm of cell, and each glucose molecule is converted into two pyruvates with help of ATP.

2. Formation of Acetyl coenzyme A:
                                                        It is a connecting link reaction between glycolysis and Kreb cycle. In this phase Each pyruvate react with Coenzyme A to become acetyl coenzyme A.

3. Kreb Cycle:
                   It occurs inside mitochondria. In this cycle each acetyl coenzyme A with fixed with CO to produce citrate which undergo in a cyclic reaction to produce ATP and NADH. . 

4. Electron transport chain:
                                           It is the last step of respiration which complete in mitochondrial membrane. In this phase most of the energy is produced along with H₂O as by product.

Conclusion:
                    It was concluded from the above discussion that the last process that takes place in respiration is electron transport chain.

The answer is hilum.