Energetics of Contraction
Energetics of Contraction
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DOI：
10.1002/cphy.c140038
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发表时间：
2015-04-01
影响因子：
5.8
通讯作者：
Barclay, C. J.
中科院分区：
文献类型：
--
作者：
Barclay, C. J.
肌肉将ATP的能量转化为有用功，可用于移动四肢和跨膜运输离子。没有转化为功的能量表现为热。在收缩开始时，当Ca 2+与肌钙蛋白-C和小清蛋白结合时也产生热。肌肉在等长收缩过程中使用ATP的速率取决于刺激的持续时间、肌肉类型、温度和肌肉长度。在等长收缩期间使用的30%至40%的ATP为将Ca 2+和Na+泵出肌质提供燃料。当缩短时，肌肉产生比等长收缩中更小的力，但以更高的速率使用ATP，并且当延长时，力输出高于等长力，但ATP分裂的速率较低。效率量化了ATP提供的能量转化为外部功的比例。每个ATP分子提供100 zJ的能量，可以转化为功。肌球蛋白跨桥的机制是这样的，在一个ATP消耗循环中最多可以做50 zJ的功;也就是说，跨桥的最大效率类似于50%。陆龟肌肉中的横桥接近这个极限，每个周期产生超过90%的可能功。其他肌肉效率较低，但收缩更快，产生更多的力量。(C)2015美国生理学会。
Muscles convert energy from ATP into useful work, which can be used to move limbs and to transport ions across membranes. The energy not converted into work appears as heat. At the start of contraction heat is also produced when Ca2+ binds to troponin-C and to parvalbumin. Muscles use ATP throughout an isometric contraction at a rate that depends on duration of stimulation, muscle type, temperature and muscle length. Between 30% and 40% of the ATP used during isometric contraction fuels the pumping Ca2+ and Na+ out of the myoplasm. When shortening, muscles produce less force than in an isometric contraction but use ATP at a higher rate and when lengthening force output is higher than the isometric force but rate of ATP splitting is lower. Efficiency quantifies the fraction of the energy provided by ATP that is converted into external work. Each ATP molecule provides 100 zJ of energy that can potentially be converted into work. The mechanics of the myosin cross-bridge are such that at most 50 zJ of work can be done in one ATP consuming cycle; that is, the maximum efficiency of a cross-bridge is similar to 50%. Cross-bridges in tortoise muscle approach this limit, producing over 90% of the possible work per cycle. Other muscles are less efficient but contract more rapidly and produce more power. (C) 2015 American Physiological Society.