Department of Biology, University of Padua, Padua, Italy; Veneto Institute of Molecular Medicine, Padua, Italy.
Department of Biology, University of Padua, Padua, Italy; Veneto Institute of Molecular Medicine, Padua, Italy.
Curr Biol. 2022 Jun 20;32(12):R618-R623. doi: 10.1016/j.cub.2022.05.006.
Mitochondria are central to cellular metabolism. They provide intermediate metabolites that are used in biosynthetic pathways and they process diet-derived nutrients into the energy-rich compound ATP. Mitochondrial ATP biosynthesis is a marvel of thermodynamic efficiency. Via the tricarboxylic acid cycle (TCA) and fatty acid β-oxidation, mitochondria extract electrons from dietary carbon compounds and pass them to nucleotides that ultimately deliver them to the respiratory chain complexes located in invaginations in the inner mitochondrial membrane (IMM) known as cristae. The respiratory chain complexes donate electrons in stepwise redox reactions to molecular oxygen and, with the exception of complex II, use the liberated energy to pump protons across the proton-impermeable IMM, generating a proton electrochemical gradient. This gradient is then utilized by the ATP synthase, which, in a rotary mechanism, catalyzes the formation of the high-energy γ-phosphate chemical bond between ADP and inorganic phosphate. The conversion of the chemical energy of carbon compounds into a physical, vectorial form of energy (the electrochemical gradient) maximizes the yield of the ATP biosynthetic process and is perhaps one of the foundations of life as we know it.
线粒体是细胞代谢的核心。它们提供中间代谢产物，这些产物被用于生物合成途径，同时将饮食来源的营养物质加工成富含能量的化合物 ATP。线粒体的 ATP 合成是热力学效率的奇迹。通过三羧酸循环（TCA）和脂肪酸β氧化，线粒体从膳食碳化合物中提取电子，并将其传递给核苷酸，最终将其传递到位于线粒体内膜（IMM）凹陷处的呼吸链复合物，这些凹陷被称为嵴。呼吸链复合物在逐步的氧化还原反应中向分子氧捐献电子，除了复合物 II 之外，它们利用释放的能量将质子泵过质子不可渗透的 IMM，产生质子电化学梯度。然后，ATP 合酶利用这个梯度，通过旋转机制催化 ADP 和无机磷酸盐之间高能γ-磷酸化学键的形成。这种将碳化合物的化学能转化为物理向量形式能量（电化学梯度）的过程最大限度地提高了 ATP 生物合成过程的产率，这也许是我们所知道的生命的基础之一。
