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 to this will be from your lab notes/procedure. it would be best to ask another student who participated in the lab as we do not know what was done, what enzyme or if the temperature is celsius or fahrenheit. if i were to guess though i'd say the rate stopped due to enzyme denturing at high temperature