Please answer ALL questions. ALL QUESTIONS please and thank you. 8) Protein kina

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Please answer ALL questions. ALL QUESTIONS please and thank you.

8) Protein kinase A (PKA) is a family of enzymes that are part of cell signal systems, and their effect is to phosphorylate proteins, altering their activity. As an example, PKA can phosphorylate the enzyme acetyl-CoA carboxylase, causing it to activate. The AG for this phosphorylation is +4.2 kcal/mol. How is ATP used to phosphorylate this enzyme, and how does phosphorylation affect enzyme activity? 9) 2,4-Dinitrophenol is an organic compound extensively used in diet pills between 1933 and 1938, but was discontinued due to side effect, though it can still be acquired illicitly. 2,4-Dinitrophenol is a protonophore, meaning it allows protons to leak across the inner mitochondrial membrane. Explain why protons are important to the mitochondria, how they are used, and why leakage of protons across the inner mitochondrial membrane would cause an increase in metabolic rates (increased rates of glycolysis and citric acid cycle, as well as increased use of oxygen).

Explanation / Answer

(9)

During oxidative phosphorylation reduced equivalents ( NADH and FADH2 )formed in glycolysis and TCA cycle are oxidized in electron transport system. As the electrons from these reduced equivalents are transferred through a series of electron carriers to the final acceptor- O2, the protons are simultaneously pumped into the intermembrane space. This builds proton gradient between the matrix of the membrane and the intermembrane space. The protons from proton motive force take place which can be conceived as water stored in a dam. The protons pass through the ATP synthase into the matrix generating ATP from ADP and Pi.

Chemical uncouplers such as dinitrophenol and FCCP dissipates proton gradient formed across the mitochondrial inner membrane. Uncouples cause the dissipation of proton motive force necessary for the ATP synthesis. Uncouplers inhibit the coupling between the electron transport and phosphorylation reactions and thus inhibit ATP synthesis without affecting the respiratory chain. Since there is a need for ATP synthesis, the glycolysis and tca cycles run at higher rates. Oxygen consumption increases because the system is uncoupled and does not require ATP synthesis to lower the proton-motive force.

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