Skeletal muscle and brain use a different NADH shuttle, the glycerol 3-phosphate shuttle. It differs from the malate-aspartate shuttle in that it delivers the reducing equivalents from NADH to ubiquinone and thus into complex III, not complex I, providing only enough energy to synthesise 1.5 ATP molecules per pair of electrons. Summing up the reaction sequence:…
The most active NADH shuttle, which functions in liver, kidney, and heart mitochondria, is the malate-aspartate shuttle. The cytosolic reducing equivalents of NADH are first transferred to the cytosolic oxaloacetate to yield malate, and this is catalysed by cytosolic malate dehydrogenase. The malate thus formed passes through the inner membrane via the malate–ketoglutarate transporter. Within the matrix,…
The NADH dehydrogenase of the inner mitochondrial membrane of animal cells can accept electrons only from NADH in the matrix. The inner membrane is not permeable to NADH. This has to be reoxidised to NAD+ by O2 via the respiratory chain. This can be overcome by the special shuttle systems carry reducing equivalents from cytosolic NADH into…
The actual measurement of the rotation of polarised light involves the use of an instrument called polariscope or polarimeter (Figure 2.8). Figure 2.8 Apparatus for Measurement of Optical Activity Because different wavelengths of polarised light are rotated differently, it is necessary to use monochromatic light. Ordinarily, the light from incandescent sodium or mercury is used. Polariscopes…
The actual measurement of the rotation of polarised light involves the use of an instrument called polariscope or polarimeter (Figure 2.8).
This is the second membrane system functioning in oxidative phosphorylation. It promotes transport of along with that of H+ from the cytosol into the matrix compartments as the entrance of the inorganic phosphate is coupled to the entrance of H+. This system is aptly designated as Pi-H+ symporter. The phosphate translocase system is specific for phosphate. Thus, the…
Optical rotation to the left, that is, laevorotation, is expressed as minus (−) and rotation to the right, that is, dextrorotation, is expressed as plus (+).
This system consists of a specific protein that extends across the inner membrane. It trans-locates one molecule of ADP inward in exchange for one molecule of ATP4-coming out. As the entrance of ADP is coupled to the exit of ATP, this system is better called ADP-ATP antiporter. Obviously, this transport system is moving more negative…
The mitochondrial outer membrane is freely permeable to most small solute molecules, but the inner membrane is impermeable to H+, OA−, K+, and also many other ionic solutes. How, then, can the ADP3 and produced in the cytosol enter the matrix and how can the newly formed ATP4− leave again, since oxidative phosphorylation takes place within the inner…
According to Mitchell, the respiratory chain is folded into three oxidation reduction loops (o/r loops) as shown in Figure 8.24. Each pair of electrons transferred from NADH to oxygen causes six protons to be translocated from inside to outside of the membrane. NADH first donates one H+ and two electrons, which together with another H+ from the internal…