Question

Question 5: Mitochondrial Function

a) Both the mitochondria and chloroplast contain electron transport chains. Describe two similarities of the electron transport chains despite being located in different organelles.

b) In the mitochondrion, the electron transport chain is normally coupled to ATP synthase. However, in endothermic animals, the electron transport chain is uncoupled from ATP synthase when temperatures drop below a certain threshold. Explain why uncoupling of the electron transport chain from ATP synthase is advantageous for an animal under cold temperature conditions.

c) Dinitrophenol is an uncoupling compound that binds to proteins in the mitochondrial electron transport chain. DNP does not stop the flow of electrons, but it does interrupt the connection between the flow of electrons and ATP synthase. At the point of its discovery, it was suggested that dinitrophenol be developed as a weight-loss medication. Explain a possible reason for considering the compound dinitrophenol as a potential weight-loss drug.

Answer 1

5.

a. Similarities of electron transport chains in mitochondria and chlorolasts are :

1. Electron transport chain creats H+ ion gradient across the inner membranes of chloroplast and mitochondria. This gradient of H+ ions is important for the generation of energy in the form of ATP.

2. Electron transport chain ultimately leads ATP synthesis in both organelles. In both cases, ATPase enzyme complexes are associated with ETC. These complexes are called Oxysomes or F0-F1 particles.

b. Ectotherms are the animals which generate their own body heat to maintain their body temperature. They keep the body temperature constant. When the temperatures are very low, these organisms uncouple the ATP synthase from ETC. This is because at low temperature, body needs more heat rather than more ATP. So, inorder to generate heat to keep the body tem[erature normal, ATP synthesis is stopped. That is why ATPase is uncoupled from ETC.

c.Dinitrophenol can be used as weight loss drug because, it intefers with the  synthesise ATP. ATP is the source of energy for various body metabolic activities. Synthesis of fatty acids requires ATP. So by decoupling ATP synthesis fatty acid synthesis also can be stopped.

DNP disturbs the H+ ion gradient and thats how prevents ATP production with the help of ATP synthases. This results in loss of energy as heat leading to hyper thermia. Lack of ATP will also lead to more carbohydrate consumption by glycolysis to generate more ATP. The process of glycolysis produce very little amount of energy than by ETC, So the body consumes carbohydrates much faster. This extra consmption of carbohydrates will lead to weight loss. Because of these reasons it can be used as weight loss drug.