蛋白质代谢必威体育精装版教程.ppt

Clinical Case Study Male infant, 2.9 kg at birth, healthy Day 3 - seizures痉挛 Mother with history of aversion to meat vomiting and lethargy嗜睡 plasma [NH4+] = 240 uM (25-40 normal) hyperammonemia mild alkalosis (pH=7.5, normal 7.35-7.45) Clinical Case Study Plasma AA gln = 2400 uM (350-650) ala = 750 uM (8-25) arg = 5 uM (30-125) cit (瓜氨酸) = undetectable Urinary orotic acid乳清酸 = 285 ug/mg creatinine (0.3-10) Clinical Case Study Oral therapy initiated EAA + arginine Sodium benzoate苯甲酸钠 Patient improves after 7 days Plasma [NH4+] normalized 蛋白质的分解代谢的主要内容 第一节 蛋白质的营养作用Nutritive value of protein 蛋白质的含氮量平均为16%，可通过测定食物的含氮量估算出蛋白质的量。 一、 氮平衡(nitrogen balance) 是测定摄入氮量和排出氮量来了解蛋白质在体内代谢和利用的一种方法。 “ Nitrogen balance refers to the difference between total nitrogen intake and total nitrogen loss in feces,urine,and perspiration.” 1.氮的总平衡(nitrogen equilibrium)： 摄入氮＝排出氮 (nitrogen intake matches output) 2.氮的正平衡(positive nitrogen balance)： 摄入氮＞排出氮 (ingestion of more nitrogen than is excreted) 3.氮的负平衡(negative nitrogen balance)： 摄入氮＜排出氮 (nitrogen output exceeds intake) 二、 蛋白质的生理需要量Physiological requirement 最小生理需要量：30-50g/d 从事中等体力劳动每天需要量：1.05g/Kg体重 Protein deficiency-kwashiorkor, generalized edema水肿and liver enlargement, abdomen bulged膨胀. 三、 蛋白质的营养价值 (nutritive value of proteins) ： 决定于氨基酸的种类、数量和比例是否与生物体组织蛋白的组成相近。 （一）必需氨基酸(essential amino acids)： 是一类不能在体内合成,必须由外界食物供给的氨基酸。 “Essential amino acids are required amino acids that cannot be synthesized by the body and must therefore be supplied by diet” 携来一两本淡色书 人体八种必需氨基酸： 缬氨酸(valine)、亮氨酸(leucine) 异亮氨酸(isoleusine) 色氨酸(tryptophan)、苏氨酸(threonine) 赖氨酸(lysine) 甲硫氨酸(蛋氨酸，methionine) ----(Cys can be made from Met)、 苯丙氨酸(phenylalanine)、 ----(Tyr