Autopsy findings showed a striking absence of subcutaneous and abdominal fat. In

Question

Autopsy findings showed a striking absence of subcutaneous and abdominal fat. In view of the clinical findings, a sample of the pesticide was tested on samples of rat mitochondria incubated in oxygenated buffer and either succinate (Fig 1a), or, malate and glutamate (Fig 1b). Figures 1a and 1b show the oxygen concentrations measured in the samples as various compounds were added to the incubation mixture.

Figure 1. Effects of adding DNOC to rat liver mitochondria.

A) Explain why the rate of oxygen consumption in both Figures 1a and 1b, increases dramatically when ADP is added to the suspension.

B) In Fig 1b, malate oxidation supplies the electrons to the electron transport chain. Why is it necessary to also supply glutamate to the suspension?

C) Why is the rate of respiration in the presence of succinate and ADP (Fig. 1a) higher than the rate of respiration in the presence of glutamate, malate, and ADP?

D) Explain the result of adding KCN to the suspension (Fig. 1a). E) Under normal conditions (No DNOC), what would happen after the addition of oligomycin? Provide a sketch of how Fig. 1b would be different.

F) What do the data allow you to conclude regarding the metabolic effect of DNOC? (Explain how your conclusion is consistent with the data shown in Fig 1a and 1b) G) Explain why: i) the victim’s body temperature was elevated ii) the victim’s respiration was elevated

H) (Bonus) Propose an explanation for why there was a striking absence of body fat found during the autopsy

Glutamate malate ieach 5 mM, ADP (1 mM) Succinate (5 mM) ADP (1 mM) DNOC (1 mM) 1O2l DNOC (1 mM) Oligomycin (5 mM) KCN (1 mM) Time Time (al (bl

Explanation / Answer

Ans A. When ADP is added the rate of oxygen consumption increases due to the oxidative phosphorylation and to yield ATP. Once the conversion to ATP is done the rate of oxygen consumption returns to normal. It is a function of electron transport chain where the conversion of ADP to ATP occurs and the oxygen consumption increases.

Ans B. The necessity of addition of glutamate to the suspension arises from the fact that glutamate posses the ability to inhibit malate dehydrogenase enzyme. The malate dehydrogenase enzyme is concerned with the malate oxidation. Hence g;utamate functions as a rate limiting step in electron transport chain. Thus glutamate is added in malate oxidation.

Ans C. On comparing the P/O ratios which is the amount of ATP produced per oxygen atom reduced by the respiratory chain, it can be concluded that the succinic acid yields more ATP as compared to the later three. IT posses a greater P/O ratio. Hence the rate of respiration in presence of succinic acid and ADP is higher as compared to the other three.

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