Question

Chapter 7: How Cells Harvest Energy

• Interpret the role of electrons, electron carriers, and ATP in energy metabolism
• Explain the purpose of oxygen in respiration
• Describe where in the cell and where in mitochondria each process of cellular respiration happens
• Summarize the initial reactants, final products and outcomes of glycolysis, pyruvate oxidation and Krebs cycle. In this summary, track the carbons, the electrons and the ATP produced.
• Illustrate the purpose of the electron transport chain, where those electrons come from and where do they end up.
• Contrasts the two mechanisms for producing ATP and their relative efficiency.
• Distinguish the process and the outcomes between aerobic and anaerobic respiration

Answer 1

1). How Cells Harvest Energy? and Describe where in the cell and where in mitochondria each process of cellular respiration happens?

From the digestive system, blood will get glucose. This glucose is transported to the cells for the release of energy. First, glucose undergo glycolysis, which takes place in cytoplasm. The energy is released in the form of both ATP and NADH and pyruvate is formed as end product. This pyruvate is then moved to the mitochondrial matrix and combine with acetyl CoA and enter in Krebs' cycle. CO2 and H2O are produced as byproduct. In the Krebs' cycle, the energy is released in the form of NADH, FADH2, and GTP. Our body depends ATP for the main energy needs. So these high energy compounds (NADH and FADH2) should be converted to ATP. This conversion is called Electron transport chain (ETC) which takes place in the inner mitochondrial membrane.

2). Interpret the role of electrons, electron carriers, and ATP in energy metabolism? Illustrate the purpose of the electron transport chain, where those electrons come from and where do they end up?

In ETC (Electron transport chain) mainly 5 complexes are involved. Complex 1,2,3,4 and ATP synthase. From the NADH the electrons are moved in to first complex and from FADH2 electrons are moved in to second complex. AT the same time they release H+ and the complex will pump the H+ in to the inter-membrane space to create proton gradient. Electrons from first and second complex is carried by ubiquinone, to the third complex. From the third complex electron is carried by cytochrome C to fourth complex.

The protons, pumped in to the inter-membrane space move to ATP synthase complex. The matrix portion of ATP synthase consists 3 conformation, open, loose and tight. So at a time one complete rotation of ATP synthase will produce 3 ATP molecules. The rotation of ATP synthase is done with the help of this H+.Each H+ will enter in to half channel and ATP synthase starts to rotates. In the matrix portion of ATP synthase, ADP combines with Pi to form ATP.

3).Explain the purpose of oxygen in respiration?

From the third complex electron is carried by cytochrome C to fourth complex. Fourth complex consists CuA, Heme A1, Heme A3, and CuB. The electrons are passed to the last portion of CuB. From CuB electrons are transferred to the oxygen, that we took during respiration. It takes place in the mitochondrial matrix. O2 will split and absorb this electron and form H2O. To prevent the free radicle formation, When 2 electrons are available in complex 4, then only it transfer the electrons in to the oxygen.