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Metabolism-Study Guide 新陈代谢-学习指南

STUDY GUIDE-METABOLISM 学习指南-新陈代谢

  1. INTRODUCTION 介绍
  1. The food we eat is our only source of energy for performing biological work.
    我们吃的食物是我们进行生物工作的唯一能量来源。
  2. There are three major metabolic destinations for the principle nutrients. They will be used for energy for active processes, synthesized into structural or functional molecules, or synthesized as fat or glycogen for later use as energy.
    主要营养素有三个主要代谢目的地。它们将被用作活性过程的能量,合成为结构或功能分子,或合成为脂肪或糖原以供以后用作能量。

  1. METABOLIC REACTIONS 代谢反应

  1. Metabolism refers to all the chemical reactions in the body.
    新陈代谢是指体内的所有化学反应。
  2. Coupling of catabolism and anabolism by ATP
    ATP 分解代谢和合成代谢的耦合
  1. Catabolism includes all chemical reactions that break down complex organic molecules while anabolism refers to chemical reactions that combine simple molecules to form complex molecules.
    分解代谢包括分解复杂有机分子的所有化学反应,而合成代谢是指将简单分子结合形成复杂分子的化学反应。
  2. The chemical reactions of living systems depend on transfer of manageable amounts of energy from one molecule to another. This transfer is usually performed by ATP.
    生命系统的化学反应取决于可管理的能量从一个分子到另一个分子的转移。这种转移通常由 ATP 进行。

  1. ENERGY TRANSFER 能量传输

  1. All molecules (nutrient molecules included) have energy stored in the bonds between their atoms.
    所有分子(包括营养分子)都将能量储存在其原子之间的键中。
  2. Oxidation-Reduction Reactions
    氧化还原反应
  1. Oxidation is the removal of electrons from a molecule and results in a decrease in the energy content of the molecule. Because most biological oxidations involve the loss of hydrogen atoms, they are called dehydrogenation reactions.
    氧化是从分子中除去电子并导致分子能量含量降低。由于大多数生物氧化涉及氢原子的损失,因此称为脱氢反应。
  1. When a substance is oxidized, the liberated hydrogen atoms do not remain free in the cell but are transferred immediately by coenzymes to another compound.
    当物质被氧化时,释放的氢原子不会在细胞中保持游离状态,而是立即通过辅酶转移到另一种化合物中。
  2. Nicotinamide adenine dinucleotide (NAD) and flavin adenine dinucleotide (FAD) are two coenzymes commonly used by living cells to carry hydrogen atoms.
    烟酰胺腺嘌呤二核苷酸(NAD)和黄素腺嘌呤二核苷酸(FAD)是活细胞常用来携带氢原子的两种辅酶。
  1. Reduction is the opposite of oxidation, that is, the addition of electrons to a molecule, and results in an increase in the energy content of the molecule.
    还原与氧化相反,即向分子添加电子,并导致分子能量含量增加。
  2. An important point to remember about oxidation-reduction reactions is that oxidation is usually an energy-releasing reaction.
    关于氧化还原反应要记住的重要一点是氧化通常是释放能量的反应。
  1. Mechanisms of ATP generation
    ATP 生成机制
  1. ATP can be generated by any of three mechanisms of phosphorylation: substrate- level phosphorylation, oxidative phosphorylation, or photophosphorylation (if chlorophyll is present).
    ATP 可以通过三种磷酸化机制中的任何一种产生:底物水平磷酸化、氧化磷酸化或光合磷酸化(如果存在叶绿素)。

  1. CARBOHYDRATE METABOLISM 碳水化合物代谢

  1. During digestion, polysaccharides and disaccharides are converted to monosaccharides (primarily glucose), which are absorbed through capillaries in villi and transported to the liver via the hepatic portal vein. Liver cells convert much of the remaining fructose and practically all of the galactose to glucose, so carbohydrate metabolism is primarily concerned with glucose metabolism.
    在消化过程中,多糖和二糖转化为单糖(主要是葡萄糖),通过绒毛中的毛细血管吸收,并通过肝门静脉转运到肝脏。肝细胞将大部分剩余的果糖和几乎所有的半乳糖转化为葡萄糖,因此碳水化合物代谢主要与葡萄糖代谢有关。
  2. Fate of Glucose 葡萄糖的命运
  1. Since glucose is the body’s preferred source for synthesizing ATP, the fate of absorbed glucose depends on the energy needs of body cells.
    由于葡萄糖是人体合成 ATP 的首选来源,因此吸收的葡萄糖的命运取决于人体细胞的能量需求。
  2. If the cells require immediate energy, they oxidize glucose to produce ATP.
    如果细胞需要立即能量,它们会氧化葡萄糖产生 ATP。
  3. Glucose can be used to form amino acids, which then can be incorporated into proteins.
    葡萄糖可用于形成氨基酸,然后氨基酸可以掺入蛋白质中。
  4. Excess glucose can be stored by the liver and skeletal muscles as glycogen, a process called glycogenesis.
    过量的葡萄糖可以被肝脏和骨骼肌储存为糖原,这一过程称为糖原生成。
  5. If glycogen storage areas are filled up, liver cells and fat cells can convert glucose to glycerol and fatty acids that can be used for synthesis of triglycerides (neutral fats) in the process of lipogenesis.
    如果糖原储存区域被填满,肝细胞和脂肪细胞可以将葡萄糖转化为甘油和脂肪酸,可用于在脂肪生成过程中合成甘油三酯(中性脂肪)。
  1. Glucose Movement into Cells
    葡萄糖进入细胞
  1. Glucose absorption in the GI tract is accomplished by secondary active transport (Na+ - glucose symporters).
    胃肠道中的葡萄糖吸收是通过次级主动转运(Na+ - 葡萄糖同向转运体)完成的。
  2. Glucose movement from blood into most other body cells occurs via facilitated diffusion transporters (Gly-T molecules). Insulin increases the insertion of Gly-T molecules into the plasma membranes, thus increasing the rate of facilitated diffusion of glucose.
    葡萄糖从血液转移到大多数其他身体细胞中是通过易化扩散转运蛋白(Gly-T 分子)发生的。胰岛素增加 Gly-T 分子插入质膜,从而增加葡萄糖的易化扩散速率。
  3. Glucose is trapped in the cell when it becomes phosphorylated.
    当葡萄糖被磷酸化时,它被捕获在细胞中。
  1. Glucose Catabolism 葡萄糖分解代谢
  1. Glucose oxidation is also called cellular respiration. It occurs in every cell of the body (except red blood cells, which lack mitochondria) and provides the cell’s chief source of energy.
    葡萄糖氧化也称为细胞呼吸。它存在于身体的每个细胞中(红细胞除外,因为红细胞缺乏线粒体),并提供细胞的主要能量来源。
  2. The complete oxidation of glucose to CO2 and H2O produces large amounts of energy and occurs in four successive stages: glycolysis, formation of acetyl coenzyme A, the Krebs cycle, and the electron transport chain.
    葡萄糖完全氧化为 CO2 和 H2O 会产生大量能量,并发生在四个连续阶段:糖酵解、乙酰辅酶 A 的形成、克雷布斯循环和电子传递链。
  1. Glycolysis 糖酵解
  1. Glycolysis refers to the breakdown of the six-carbon molecule, glucose, into two three-carbon molecules of pyruvic acid
    糖酵解是指六碳分子葡萄糖分解成两个三碳分子丙酮酸
  2. The reactions of glycolysis use two ATP molecules, but produce four, a net gain of two.
    糖酵解反应使用两个 ATP 分子,但产生四个,净增益为两个。
  3. Summarizes the 10 reactions of Glycolysis.
    总结了糖酵解的 10 个反应。
  1. Fate of pyruvic acid 丙酮酸的命运
  1. When oxygen is in short supply, pyruvic acid is reduced to lactic acid. Under aerobic conditions, pyruvic acid is converted to acetyl coenzyme A and enters the Krebs cycle. Thus, the fate of pyruvic acid depends on the availability of O2.
    当氧气供应不足时,丙酮酸会还原为乳酸。在有氧条件下,丙酮酸转化为乙酰辅酶A并进入克雷布斯循环。因此,丙酮酸的命运取决于氧气的可用性。
  1. Formation of Acetyl Coenzyme A
    乙酰辅酶A的形成
  1. Pyruvic acid is prepared for entrance into the Krebs cycle by conversion to a two-carbon compound (acetyl group) followed by the addition of coenzyme A (CoA) to form acetyl coenzyme A (acetyl CoA).
    丙酮酸通过转化为二碳化合物(乙酰基),然后添加辅酶 A (CoA) 形成乙酰辅酶 A (乙酰 CoA),准备进入克雷布斯循环。
  2. Coenzyme A is derived from pantothenic acid, a B vitamin.
    辅酶 A 源自泛酸,一种 B 族维生素。
  1. Krebs Cycle 克雷布斯循环
  1. The Krebs cycle is also called the citric acid cycle, or the tricarboxylic acid (TCA) cycle. It is a series of biochemical reactions that occur in the matrix of mitochondria.
    克雷布斯循环也称为柠檬酸循环或三羧酸(TCA)循环。它是在线粒体基质中发生的一系列生化反应。
  2. The large amount of chemical potential energy stored in intermediate substances derived from pyruvic acid is released step by step.
    丙酮酸衍生的中间物质中储存的大量化学势能被逐步释放。
  3. The Krebs cycle involves decarboxylations and oxidations and reductions of various organic acids.
    克雷布斯循环涉及各种有机酸的脱羧、氧化和还原。
  4. For every two molecules of acetyl CoA that enter the Krebs cycle, 6 NADH, 6 H+, and 2 FADH2 are produced by oxidation-reduction reactions, and two molecules of ATP are generated by substrate- level phosphorylation.
    对于进入克雷布斯循环的每两分子乙酰辅酶A,通过氧化还原反应产生6个NADH、6个H+和2个FADH2,并通过底物水平磷酸化产生两分子ATP。
  5. The energy originally in glucose and then in pyruvic acid is primarily in the reduced coenzymes NADH + H+ and FADH2.
    最初在葡萄糖中然后在丙酮酸中的能量主要在还原型辅酶 NADH + H+ 和 FADH2 中。
  6. Summarizes the eight reactions of the Krebs cycle.
    总结克雷布斯循环的八个反应。
  1. Electron Transport Chain 电子传输链
  1. The electron transport chain involves a sequence of electron carrier molecules on the inner mitochondrial membrane capable of a series of oxidation-reduction reactions.
    电子传递链涉及线粒体内膜上的一系列电子载体分子,能够进行一系列氧化还原反应。
  1. As electrons are passed through the chain, there is a stepwise release of energy from the electrons for the generation of ATP.
    当电子通过链条时,电子会逐步释放能量以产生 ATP。
  2. In aerobic cellular respiration, the last electron receptor of the chain is molecular oxygen (O2). This final oxidation is irreversible.
    在有氧细胞呼吸中,链的最后一个电子受体是分子氧(O2)。最终氧化是不可逆的。
  1. The process involves a series of oxidation-reduction reactions in which the energy in NADH + H+ and FADH2 is liberated and transferred to ATP for storage.
    该过程涉及一系列氧化还原反应,其中 NADH + H+ 和 FADH2 中的能量被释放并转移到 ATP 中进行储存。
  1. This mechanism of ATP generation links chemical reactions (electrons passing along the electron chain) with pumping of hydrogen ion.
    这种 ATP 生成机制将化学反应(电子沿着电子链传递)与氢离子的泵送联系起来。
  2. It is called chemiosmosis.
    这称为化学渗透。
  1. The carrier molecules involved include flavin mononucleotide, cytochromes, iron-sulfur centers, copper atoms, and ubiquinones (also coenzyme Q).
    涉及的载体分子包括黄素单核苷酸、细胞色素、铁硫中心、铜原子和泛醌(也称为辅酶Q)。
  2. Within the inner mitochondrial membrane, the carriers of the electron transport chain cluster into three complexes, each of which acts as a proton pump that expels H+ from the mitochondrial matrix and helps create an electrochemical gradient of H+.
    在线粒体内膜内,电子传递链的载体聚集成三个复合物,每个复合物充当质子泵,将 H+ 从线粒体基质中排出,并有助于产生 H+ 的电化学梯度。
  1. Summary of Cellular Respiration
    细胞呼吸总结
  1. The complete oxidation of glucose can be represented as follows: C6H12O6 + 6O2 => 36 or 38ATP + 6CO2 +6H2O
    葡萄糖的完全氧化可表示为: C6H12O6 + 6O2 => 36 或 38ATP + 6CO2 +6H2O
  2. During aerobic respiration, 36 or 38 ATPs can be generated from one molecule of glucose. Two of those ATPs come from substrate- level phosphorylation in glycolysis and two come from substrate- level phosphorylation in the Krebs cycle.
    在有氧呼吸过程中,一分子葡萄糖可产生 36 或 38 个 ATP。其中两个 ATP 来自糖酵解中的底物水平磷酸化,另外两个来自克雷布斯循环中的底物水平磷酸化。
  3. Summarizes the ATP yield during aerobic respiration.
    总结有氧呼吸期间的 ATP 产量。
  4. Summarizes the sites of the principal events of the various stages of cellular respiration.
    总结了细胞呼吸各个阶段的主要事件的地点。
  1. Glucose Anabolism 葡萄糖合成代谢
  1. The conversion of glucose to glycogen for storage in the liver and skeletal muscle is called glycogenesis. The process occurs in the liver and is stimulated by insulin.
    葡萄糖转化为糖原并储存在肝脏和骨骼肌中的过程称为糖原生成。该过程发生在肝脏中并受到胰岛素的刺激。
  2. The conversion of glycogen back to glucose is called glycogenolysis. This process occurs between meals and is stimulated by glucagon and epinephrine.
    糖原转化回葡萄糖的过程称为糖原分解。这个过程发生在两餐之间,并受到胰高血糖素和肾上腺素的刺激。
  3. Carbohydrate loading by eating large amounts of complex carbohydrates maximizes the amount of energy available for exercise.
    通过食用大量复合碳水化合物来补充碳水化合物可以最大限度地提高运动所需的能量。
  4. Gluconeogenesis is the conversion of protein or fat molecules into glucose.
    糖异生是将蛋白质或脂肪分子转化为葡萄糖。
  1. Glycerol (from fats) may be converted to glyceraldehyde-3-phosphate and some amino acids may be converted to pyruvic acid. Both of these compounds may enter the Krebs cycle to provide energy.
    甘油(来自脂肪)可以转化为甘油醛-3-磷酸,一些氨基酸可以转化为丙酮酸。这两种化合物都可能进入克雷布斯循环以提供能量。
  2. Gluconeogenesis is stimulated by cortisol, thyroid hormone, epinephrine, glucagon, and human growth hormone.
    糖异生受到皮质醇、甲状腺激素、肾上腺素、胰高血糖素和人类生长激素的刺激。
  1. LIPID METABOLISM 脂质代谢

  1. Transport of Lipids by Lipoproteins
    脂蛋白转运脂质
  1. Most lipids are transported in the blood in combination with proteins as lipoproteins. Four classes of lipoproteins are chylomicrons, very low-density lipoproteins (VLDLs), low-density lipoproteins (LDLs), and high-density lipoproteins (HDLs).
    大多数脂质在血液中与蛋白质作为脂蛋白结合运输。脂蛋白分为四类:乳糜微粒、极低密度脂蛋白(VLDL)、低密度脂蛋白(LDL)和高密度脂蛋白(HDL)。
  1. Chylomicrons form in small intestinal mucosal cells and contain exogenous (dietary) lipids. They enter villi lacteals, are carried into the systemic circulation into adipose tissue where their triglyceride fatty acids are released and stored in the adipocytes and used by muscle cells for ATP production.
    乳糜微粒在小肠粘膜细胞中形成并含有外源(膳食)脂质。它们进入绒毛乳腺,被带入体循环进入脂肪组织,在那里它们的甘油三酯脂肪酸被释放并储存在脂肪细胞中,并被肌肉细胞用于产生 ATP。
  2. VLDLs contain endogenous triglycerides. They are transport vehicles that carry triglycerides synthesized in hepatocytes to adipocytes for storage. VLDLs are converted to LDLs.
    VLDL 含有内源性甘油三酯。它们是将肝细胞中合成的甘油三酯运送到脂肪细胞进行储存的运输工具。 VLDL 转换为 LDL。
  3. LDLs carry about 75% of total blood cholesterol and deliver it to cells throughout the body. When present in excessive numbers, LDLs deposit cholesterol in and around smooth muscle fibers in arteries.
    低密度脂蛋白携带约 75% 的血液总胆固醇,并将其输送到全身细胞。当低密度脂蛋白含量过多时,胆固醇会沉积在动脉平滑肌纤维内和周围。
  4. HDLs remove excess cholesterol from body cells and transport it to the liver for elimination.
    高密度脂蛋白从身体细胞中清除多余的胆固醇,并将其运输到肝脏进行消除。
  1. There are two sources of cholesterol in the body: food we eat and liver synthesis.
    体内胆固醇有两个来源:我们吃的食物和肝脏合成。
  1. For adults, desirable levels of blood cholesterol are TC (total cholesterol) under 200 mg/dl, LDL under 130 mg/dl, and HDL over 40 mg/dl. Normally, triglycerides are in the range of 10-190 mg/dl.
    对于成年人来说,理想的血液胆固醇水平是 TC(总胆固醇)低于 200 mg/dl,LDL 低于 130 mg/dl,HDL 高于 40 mg/dl。通常,甘油三酯在 10-190 mg/dl 范围内。
  2. Among the therapies used to reduce blood cholesterol level are exercise, diet, and drugs.
    用于降低血液胆固醇水平的疗法包括运动、饮食和药物。
  1. Fate of Lipids 脂质的命运
  1. Some lipids may be oxidized to produce ATP.
    一些脂质可能被氧化产生 ATP。
  2. Some lipids are stored in adipose tissue.
    一些脂质储存在脂肪组织中。
  3. Other lipids are used as structural molecules or to synthesize essential molecules. Examples include phospholipids of plasma membranes, lipoproteins that transport cholesterol, thromboplastin for blood clotting, and cholesterol used to synthesize bile salts and steroid hormones.
    其他脂质用作结构分子或合成必需分子。例子包括质膜磷脂、转运胆固醇的脂蛋白、用于凝血的凝血活酶以及用于合成胆汁盐和类固醇激素的胆固醇。
  4. The various functions of lipids in the body.
    脂质在体内的多种功能。
  1. Triglyceride Storage 甘油三酯储存
  1. Triglycerides are stored in adipose tissue, mostly in the subcutaneous layer.
    甘油三酯储存在脂肪组织中,大部分在皮下层。
  2. Adipose cells contain lipases that catalyze the deposition of fats from chylomicrons and hydrolyze neutral fats into fatty acids and glycerol.
    脂肪细胞含有脂肪酶,可催化乳糜微粒中的脂肪沉积,并将中性脂肪水解成脂肪酸和甘油。
  3. Fats in adipose tissue are not inert. They are catabolized and mobilized constantly throughout the body.
    脂肪组织中的脂肪不是惰性的。它们在全身不断分解代谢和动员。
  1. Lipid Catabolism: Lipolysis
    脂质分解代谢:脂肪分解
  1. Triglycerides are split into fatty acids and glycerol (a process called lipolysis) under the influence of hormones such as epinephrine, norepinephrine, and glucocorticoids and released from fat deposits. Glycerol and fatty acids are then catabolized separately.
    在肾上腺素、去甲肾上腺素和糖皮质激素等激素的影响下,甘油三酯分解为脂肪酸和甘油(这一过程称为脂肪分解),并从脂肪沉积物中释放出来。然后甘油和脂肪酸分别分解代谢。
  2. Glycerol can be converted into glucose by conversion into glyceraldehyde-3- phosphate.
    甘油可通过转化为3-磷酸甘油醛而转化为葡萄糖。
  3. In beta oxidation, carbon atoms are removed in pairs from fatty acid chains. The resulting molecules of acetyl coenzyme A enter the Krebs cycle.
    在β氧化中,碳原子从脂肪酸链上成对去除。由此产生的乙酰辅酶 A 分子进入克雷布斯循环。
  1. As a part of normal fatty acid catabolism two acetyl CoA molecules can form acetoacetic acid, which can then be converted to beta- hydroxybutyric acid and acetone.
    作为正常脂肪酸分解代谢的一部分,两个乙酰辅酶A分子可以形成乙酰乙酸,然后乙酰乙酸可以转化为β-羟基丁酸和丙酮。
  2. These three substances are known as ketone bodies and their formation is called ketogenesis.
    这三种物质称为酮体,它们的形成称为生酮。
  1. Lipid Anabolism: Lipogenesis
    脂质合成代谢:脂肪生成
  1. The conversion of glucose or amino acids into lipids is called lipogenesis. The process is stimulated by insulin.
    葡萄糖或氨基酸转化为脂质的过程称为脂肪生成。该过程是由胰岛素刺激的。
  2. The intermediary links in lipogenesis are glyceraldehyde-3-phosphate and acetyl coenzyme A.
    脂肪生成的中间环节是3-磷酸甘油醛和乙酰辅酶A。
  3. An excess of ketone bodies, called ketosis, may cause acidosis or abnormally low blood pH.
    酮体过量(称为酮症)可能会导致酸中毒或血液 pH 值异常低。

  1. PROTEIN METABOLISM 蛋白质代谢

  1. During digestion, proteins are hydrolyzed into amino acids. Amino acids are absorbed by the capillaries of villi and enter the liver via the hepatic portal vein.
    在消化过程中,蛋白质被水解成氨基酸。氨基酸被绒毛毛细血管吸收并通过肝门静脉进入肝脏。
  2. Fate of Proteins 蛋白质的命运
  1. Amino acids, under the influence of human growth hormone and insulin, enter body cells by active transport.
    氨基酸在人体生长激素和胰岛素的影响下,通过主动运输进入人体细胞。
  2. Inside cells, amino acids are synthesized into proteins that function as enzymes, transport molecules, antibodies, clotting chemicals, hormones, contractile elements in muscle fibers, and structural elements. They may also be stored as fat or glycogen or used for energy.
    在细胞内,氨基酸被合成为蛋白质,这些蛋白质具有酶、转运分子、抗体、凝血化学物质、激素、肌纤维中的收缩元件和结构元件的功能。它们也可以作为脂肪或糖原储存或用作能量。
  1. Protein Catabolism 蛋白质分解代谢
  1. Before amino acids can be catabolized, they must be converted to substances that can enter the Krebs cycle. These conversions involve deamination, decarboxylation, and hydrogenation.
    在氨基酸被分解代谢之前,它们必须转化为可以进入三羧酸循环的物质。这些转化涉及脱氨、脱羧和氢化。
  2. Amino acids can be converted into glucose, fatty acids, and ketone bodies.
    氨基酸可以转化为葡萄糖、脂肪酸和酮体。
  1. Protein Anabolism 蛋白质合成代谢
  1. Protein anabolism involves the formation of peptide bonds between amino acids to produce new proteins.
    蛋白质合成代谢涉及氨基酸之间肽键的形成以产生新蛋白质。
  2. Protein synthesis is stimulated by human growth hormone, thyroxine, and insulin.
    人类生长激素、甲状腺素和胰岛素会刺激蛋白质合成。
  3. Protein synthesis is carried out on the ribosomes of almost every cell in the body, directed by the cells’ DNA and RNA.
    蛋白质合成是在体内几乎每个细胞的核糖体上进行的,由细胞的 DNA 和 RNA 指导。
  4. Of the 20 amino acids in your body, 10 are referred to as essential amino acids. These amino acids cannot be synthesized by the human body from molecules present within the body. They are synthesized by plants or bacteria. Food containing these amino acids are “essential” for human growth and must be a part of the diet.
    在您体内的 20 种氨基酸中,有 10 种被称为必需氨基酸。这些氨基酸不能由人体从体内存在的分子合成。它们是由植物或细菌合成的。含有这些氨基酸的食物对于人体生长是“必需的”,必须成为饮食的一部分。
  5. Nonessential amino acids can be synthesized by body cells through a process called transamination. Once the appropriate essential and nonessential amino acids are present in cells, protein synthesis occurs rapidly.
    非必需氨基酸可以由体细胞通过称为转氨作用的过程合成。一旦细胞中存在适当的必需氨基酸和非必需氨基酸,蛋白质合成就会迅速发生。
  6. Phenylketonuria (PKU) is a genetic error of protein metabolism characterized by elevated blood levels of the amino acid phenylalanine. It is caused by a mutation in the gene that codes for the enzyme phenylalanine hydrolylase. This enzyme is needed to convert phenylalanine to tyrosine (Clinical Connection).
    苯丙酮尿症 (PKU) 是一种蛋白质代谢遗传错误,其特征是血液中氨基酸苯丙氨酸水平升高。它是由编码苯丙氨酸水解酶的基因突变引起的。将苯丙氨酸转化为酪氨酸需要这种酶(临床连接)。

  1. KEY MOLECULES AT METABOLIC CROSSROADS
    代谢十字路口的关键分子

  1. Although there are thousands of different chemicals in your cells, three molecules play key roles in metabolism: glucose-6-phosphate, pyruvic acid, and acetyl CoA.
    尽管细胞中有数千种不同的化学物质,但三种分子在新陈代谢中发挥着关键作用:葡萄糖-6-磷酸、丙酮酸和乙酰辅酶A。
  2. Role of Glucose-6-phosphate
    6-磷酸葡萄糖的作用
  1. Glucose-6-phosphate can be used to synthesize glycogen or glucose, make ribose-5-phosphate for the synthesis of RNA and DNA, and be converted to pyruvate via glycolysis.
    6-磷酸葡萄糖可用于合成糖原或葡萄糖,制造5-磷酸核糖用于合成RNA和DNA,并通过糖酵解转化为丙酮酸。
  1. Role of Pyruvic acid 丙酮酸的作用
  1. Production of lactic acid
    乳酸生产
  2. Production of alanine 丙氨酸的生产
  3. Gluconeogenesis 糖异生
  1. Role of Acetyl coenzyme A
    乙酰辅酶A的作用
  1. When ATP is low and oxygen is plentiful, pyruvic acid is converted to acetyl coenzyme A. When oxygen supply is low, pyruvic acid is converted to lactic acid. One link between carbohydrate and protein metabolism is via pyruvic acid.
    当 ATP 较低且氧气充足时,丙酮酸会转化为乙酰辅酶 A。当氧气供应较低时,丙酮酸会转化为乳酸。碳水化合物和蛋白质代谢之间的联系之一是通过丙酮酸。
  2. Acetyl coenzyme A is the gateway into the Krebs cycle and is also used to synthesize fatty acids, ketone bodies, and cholesterol.
    乙酰辅酶 A 是进入克雷布斯循环的门户,也用于合成脂肪酸、酮体和胆固醇。
  1. Summarizes carbohydrate, lipid, and protein metabolism
    总结碳水化合物、脂质和蛋白质代谢

  1. METABOLIC ADAPTATIONS 代谢适应

  1. Your metabolic reactions depend on how recently you have eaten. During the absorptive state, which alternates with the postabsorptive state, ingested nutrients enter the blood and lymph from the GI tract, and glucose is readily available for ATP production.
    您的代谢反应取决于您最近进食的时间。在吸收状态(与吸收后状态交替)期间,摄入的营养物质从胃肠道进入血液和淋巴液,并且葡萄糖很容易用于 ATP 的产生。
  1. An average meal requires about 4 hours for complete absorption, and given three meals a day, the body spends about 12 hours of each day in the absorptive state. (The other 12 hours, during late morning, late afternoon, and most of the evening, are spent in the postabsorptive state.)
    一顿饭平均需要4个小时左右才能完全吸收,一日三餐,身体每天大约有12个小时处于吸收状态。 (另外 12 个小时,上午晚些时候、下午晚些时候和晚上的大部分时间,都处于吸收后状态。)
  2. Hormones are the major regulators of reactions during each state.
    激素是每种状态下反应的主要调节剂。
  1. Metabolism During the Absorptive State
    吸收状态下的新陈代谢
  1. Several things typically happen during the absorptive state.
    在吸收状态期间通常会发生一些事情。
  1. Most body cells produce ATP by oxidizing glucose to carbon dioxide and water.
    大多数身体细胞通过将葡萄糖氧化成二氧化碳和水来产生 ATP。
  2. Glucose transported to the liver is converted to glycogen or triglycerides. Little is oxidized for energy.
    转运到肝脏的葡萄糖转化为糖原或甘油三酯。很少被氧化以获取能量。
  3. Most dietary lipids are stored in adipose tissue.
    大多数膳食脂质储存在脂肪组织中。
  4. Amino acids in liver cells are converted to carbohydrates, fats, and proteins.
    肝细胞中的氨基酸转化为碳水化合物、脂肪和蛋白质。
  1. Regulation of Metabolism During the Absorptive State
    吸收状态下新陈代谢的调节
  1. Soon after eating, gastric inhibitory peptide and the rise in blood glucose concentration stimulate insulin release from pancreatic beta cells. In several ways, insulin stimulates absorptive state metabolism.
    进食后不久,抑胃肽和血糖浓度升高会刺激胰腺β细胞释放胰岛素。胰岛素通过多种方式刺激吸收状态代谢。
  2. Summarizes the hormonal regulation of metabolism in the absorptive state.
    总结吸收状态下新陈代谢的激素调节。
  1. Metabolism During the Postabsorptive State
    吸收后状态下的新陈代谢
  1. During the postabsorptive state, absorption is complete, and the energy needs of the body must be satisfied by nutrients already present in the body
    在吸收后状态期间,吸收完成,身体的能量需求必须由体内已有的营养物质来满足
  1. The major concern of the body during the postabsorptive state is to maintain normal blood glucose level (70 to 110 mg/100 ml of blood).
    在吸收后状态期间,身体主要关心的是维持正常的血糖水平(70 至 110 毫克/100 毫升血液)。
  2. Homeostasis of blood glucose concentration is especially important for the nervous system and red blood cells.
    血糖浓度的稳态对于神经系统和红细胞尤其重要。
  1. The dominant fuel molecule for ATP production in the nervous system is glucose, because fatty acids are unable to pass the blood- brain barrier.
    神经系统中产生 ATP 的主要燃料分子是葡萄糖,因为脂肪酸无法通过血脑屏障。
  2. Red blood cells derive all of their ATP from glycolysis of glucose because they lack mitochondria and thus lack the Krebs cycle and electron transport chain.
    红细胞的所有 ATP 均来自葡萄糖的糖酵解,因为它们缺乏线粒体,因此缺乏克雷布斯循环和电子传递链。
  1. Postabsorptive State Reactions
    吸收后状态反应
  1. Reactions that produce glucose are the breakdown of liver glycogen, gluconeogenesis using lactic acid, and gluconeogenesis using amino acids.
    产生葡萄糖的反应包括肝糖原的分解、使用乳酸的糖异生和使用氨基酸的糖异生。
  2. Reactions that produce ATP without using glucose are oxidation of fatty acids, oxidation of lactic acid, oxidation of amino acids, oxidation of ketone bodies, and breakdown of muscle glycogen.
    不使用葡萄糖产生 ATP 的反应有脂肪酸氧化、乳酸氧化、氨基酸氧化、酮体氧化和肌糖原分解。
  1. Regulation of Metabolism During the Postabsorptive State
    吸收后状态代谢的调节
  1. The hormones that stimulate metabolism in the postabsorptive state sometimes are called anti-insulin hormones because they counter the insulin effects that dominate the absorptive state. The most important anti-insulin hormone is glucagon.
    在吸收后状态下刺激新陈代谢的激素有时被称为抗胰岛素激素,因为它们可以抵消主导吸收状态的胰岛素作用。最重要的抗胰岛素激素是胰高血糖素。
  2. A low blood glucose level also activates the sympathetic branch of the ANS.
    低血糖水平也会激活 ANS 的交感神经分支。
  3. Summarizes hormonal regulation of metabolism in the postabsorptive state.
    总结吸收后状态下新陈代谢的激素调节。
  1. Metabolism During Fasting and Starvation
    禁食和饥饿期间的新陈代谢
  1. Fasting means going without food for many hours or a few days; starvation means weeks or months of food deprivation or inadequate food intake.
    禁食意味着数小时或数天不进食;饥饿是指数周或数月的食物匮乏或食物摄入不足。
  1. Catabolism of stored triglycerides and structural proteins can provide energy for several weeks.
    储存的甘油三酯和结构蛋白的分解代谢可以提供几周的能量。
  2. The amount of adipose tissue determines the lifespan possible without food.
    脂肪组织的数量决定了在没有食物的情况下可能的寿命。
  1. During fasting and starvation, nervous tissue and red blood cells continue to use glucose for ATP production.
    在禁食和饥饿期间,神经组织和红细胞继续利用葡萄糖来产生 ATP。
  2. During prolonged fasting, large amounts of amino acids from tissue protein breakdown (primarily from skeletal muscle) are released and converted to glucose in the liver by gluconeogenesis.
    在长时间禁食期间,组织蛋白分解(主要来自骨骼肌)产生的大量氨基酸被释放,并通过糖异生在肝脏中转化为葡萄糖。
  3. The most dramatic metabolic change that occurs with fasting and starvation is the increase in formation of ketone bodies by hepatocytes.
    禁食和饥饿时发生的最显着的代谢变化是肝细胞酮体形成的增加。
  1. Ketogenesis increases as catabolism of fatty acids rises.
    随着脂肪酸分解代谢的增加,生酮作用也会增加。
  2. The presence of ketones actually reduces the use of glucose for ATP production, which in turn decreases the demand for gluconeogenesis and slows the catabolism of muscle proteins.
    酮的存在实际上减少了用于 ATP 生产的葡萄糖的使用,这反过来又减少了对糖异生的需求并减缓了肌肉蛋白质的分解代谢。

  1. ENERGY BALANCE 能量平衡

  1. A normal body temperature is maintained by a delicate balance between heat-producing and heat-losing mechanisms.
    正常体温是通过产热和散热机制之间的微妙平衡来维持的。
  2. Food Calories 食物热量
  1. Heat is a form of kinetic energy that can be measured as temperature and expressed in units called calories.
    热量是动能的一种形式,可以以温度的形式测量,并以卡路里的单位表示。
  1. A calorie, spelled with a little c, is the amount of heat energy required to raise the temperature of 1 gram of water from 140C to 150C.
    一卡路里,拼写为小c,是将1克水的温度从140°C提高到150°C所需的热能。
  2. A kilocalorie or Calorie, spelled with a capital C, is equal to 1000 calories
    千卡或卡路里,以大写字母 C 拼写,等于 1000 卡路里
  1. Metabolic Rate 代谢率
  1. The overall rate at which heat is produced is the metabolic rate.
    产生热量的总速率就是代谢率。
  1. Measurement of the metabolic rate under basal conditions is called the basal metabolic rate (BMR).
    基础代谢率的测量称为基础代谢率(BMR)。
  2. BMR is a measure of the rate at which the quiet, resting, fasting body breaks down nutrients to liberate energy.
    BMR 是衡量安静、休息、禁食的身体分解营养物质以释放能量的速率的指标。
  3. BMR is also a measure of how much thyroxine the thyroid gland is producing, since thyroxine regulates the rate of ATP use and is not a controllable factor under basal conditions.
    BMR 也是甲状腺产生多少甲状腺素的指标,因为甲状腺素调节 ATP 使用率,并且在基础条件下不是一个可控因素。
  1. Total Metabolic Rate 总代谢率
  1. TMR: Total energy expenditure by the body per unit of time
    TMR:身体每单位时间消耗的总能量
  1. Adipose and Tissue and Stored Chemical Energy
    脂肪和组织以及储存的化学能
  1. Adipose tissue is major sites of chemical energy
    脂肪组织是化学能的主要场所
  1. Regulation of Food Intake
    食物摄入量的调节
  1. The feeding (hunger) center and the satiety center are two centers in the hypothalamus related to the regulation of food intake. The feeding center is constantly active but may be inhibited by the satiety center.
    摄食(饥饿)中枢和饱足中枢是下丘脑中与食物摄入调节相关的两个中枢。进食中枢持续活跃,但可能受到饱足中枢的抑制。
  2. The hormone leptin acts on the hypothalamus to inhibit circuits that stimulate eating and to activate circuits that increase energy expenditure.
    瘦素激素作用于下丘脑,抑制刺激进食的回路,并激活增加能量消耗的回路。
  3. Other stimuli that affect the feeding and satiety centers are glucose, amino acids, lipids, body temperature, distention of the GI tract, and choleocystokinin.
    其他影响进食和饱腹感中枢的刺激包括葡萄糖、氨基酸、脂质、体温、胃肠道扩张和胆囊收缩素。
  4. Eating in response to emotions is called emotional eating. Problems arise when emotional eating becomes so excessive that it interferes with health.
    根据情绪而进食被称为情绪饮食。当情绪化饮食变得过度以至于干扰健康时,就会出现问题。
  1. Regulation of Body Temperature
    体温调节
  1. If the amount of heat production equals the amount of heat loss, one maintains a constant core temperature near 370C (98.60F).
    如果产生的热量等于热量损失的量,则核心温度会保持在 37 0 C (98.6 0 F) 附近。
  1. Core temperature refers to the body’s temperature in body structures below the skin and subcutaneous tissue.
    核心温度是指皮肤和皮下组织以下的身体结构的温度。
  2. Shell temperature refers to the body’s temperature at the surface, that is, the skin and subcutaneous tissue.
    外壳温度是指人体表面,即皮肤和皮下组织的温度。
  3. Too high a core temperature kills by denaturing body proteins, while too low a core temperature causes cardiac arrhythmias that can result in death.
    核心温度过高会导致体内蛋白质变性而导致死亡,而核心温度过低则会导致心律失常,从而导致死亡。
  1. Heat Production 产热
  1. The production of body heat is influenced by metabolic rate and responses that occur when body temperature starts to fall.
    身体热量的产生受到新陈代谢率和体温开始下降时发生的反应的影响。
  2. Factors that affect metabolic rate include exercise, hormones, the nervous system, body temperature, ingestion of food, age, and other factors such as gender, climate, sleep, and malnutrition.
    影响代谢率的因素包括运动、激素、神经系统、体温、食物摄入、年龄以及性别、气候、睡眠和营养不良等其他因素。
  3. Heat conservation mechanisms include vasoconstriction, sympathetic stimulation, skeletal muscle contraction (shivering), and thyroid hormone production.
    保温机制包括血管收缩、交感神经刺激、骨骼肌收缩(颤抖)和甲状腺激素的产生。
  1. Mechanisms of Heat Transfer: Heat is lost from the body by radiation, evaporation, conduction, and convection.
    传热机制:热量通过辐射、蒸发、传导和对流从体内散失。
  1. Radiation is the transfer of heat from a warmer object to a cooler object without physical contact.
    辐射是指在没有物理接触的情况下将热量从较热的物体传递到较冷的物体。
  2. Evaporation is the conversion of a liquid to a vapor. Water evaporating from the skin takes with it a great deal of heat. The rate of evaporation is inversely related to relative humidity.
    蒸发是液体转化为蒸气。水从皮肤蒸发会带走大量的热量。蒸发速率与相对湿度成反比。
  3. Conduction is the transfer of body heat to a substance or object in contact with the body, such as chairs, clothing, jewelry, air, or water.
    传导是将身体热量传递到与身体接触的物质或物体,例如椅子、衣服、珠宝、空气或水。
  4. Convection is the transfer of body heat by a liquid or gas between areas of different temperature.
    对流是液体或气体在不同温度区域之间传递身体热量。
  1. Hypothalmic Thermostat 下丘脑恒温器
  1. The hypothalmic thermostat is the preoptic area.
    下丘脑恒温器是视前区。
  2. Nerve impulses from the preoptic area propagate to other parts of the hypothalamus known as the heat-losing center and the heat-promoting center.
    来自视前区的神经冲动传播到下丘脑的其他部分,称为散热中心和散热中心。
  1. Several negative feedback loops work to raise body temperature when it drops too low or raises too high.
    当体温降得太低或升得太高时,几个负反馈回路会起作用,以提高体温。
  2. Hypothermia refers to a lowering of body temperature to 350C (950F) or below. It may be caused by an overwhelming cold stress, metabolic disease, drugs, burns, malnutrition, transection of the cervical spinal cord, and/or lowering of body temperature for surgery.
    体温过低是指体温降至 350C (950F) 或以下。它可能是由压倒性的冷应激、代谢疾病、药物、烧伤、营养不良、颈脊髓横断和/或手术降低体温引起的。

  1. NUTRITION 营养

  1. Guidelines for healthy eating include eating a variety of foods; maintaining healthy weight; choosing foods low in fat, saturated fat, and cholesterol; eating plenty of vegetables, fruits, and grain products; using sugar only in moderation; using salt and sodium only in moderation; and drinking alcohol only in moderation or not at all.
    健康饮食指南包括吃多种食物;保持健康的体重;选择低脂肪、饱和脂肪和胆固醇的食物;多吃蔬菜、水果、谷类制品;仅适量使用糖;仅适量使用盐和钠;适量饮酒或根本不饮酒。
  1. The Food Guide Pyramid shows how many servings of the five major food groups to eat each day.
    食物指南金字塔显示了每天要吃多少份五种主要食物。
  2. Foods high in complex carbohydrates serve as the base of the pyramid since they should be consumed in largest quantity.
    富含复合碳水化合物的食物是金字塔的底部,因为它们应该被大量食用。
  1. Minerals are inorganic substances that help regulate body processes.
    矿物质是有助于调节身体过程的无机物质。
  1. Minerals known to perform essential functions include calcium, phosphorus, sodium, chlorine, potassium, magnesium, iron, sulfur, iodine, manganese, cobalt, copper, zinc, selenium, and chromium.
    已知具有基本功能的矿物质包括钙、磷、钠、氯、钾、镁、铁、硫、碘、锰、钴、铜、锌、硒和铬。
  1. Vitamins are organic nutrients that maintain growth and normal metabolism. Many function in enzyme systems as coenzymes.
    维生素是维持生长和正常新陈代谢的有机营养素。许多在酶系统中作为辅酶发挥作用。
  1. Most vitamins cannot be synthesized by the body. No single food contains all of the required vitamins—one of the best reasons for eating a varied diet.
    大多数维生素不能由人体合成。没有一种食物含有所有必需的维生素——这是多样化饮食的最佳理由之一。
  2. Based on solubility, vitamins fall into two main groups: fat-soluble and water- soluble.
    根据溶解度,维生素主要分为两大类:脂溶性维生素和水溶性维生素。
  1. Fat-soluble vitamins are emulsified into micelles and absorbed along with ingested dietary fats by the small intestine. They are stored in cells (particularly liver cells) and include vitamins A, D, E, and K.
    脂溶性维生素被乳化成胶束并与摄入的膳食脂肪一起被小肠吸收。它们储存在细胞(特别是肝细胞)中,包括维生素 A、D、E 和 K。
  2. Water-soluble vitamins are absorbed along with water in the GI tract and dissolve in the body fluids. Excess quantities of these vitamins are excreted in the urine. The body does not store water-soluble vitamins (such as B vitamins and vitamin C) well.
    水溶性维生素在胃肠道中与水一起被吸收并溶解在体液中。过量的这些维生素会通过尿液排出。身体不能很好地储存水溶性维生素(如 B 族维生素和维生素 C)。
  3. Vitamins C, E, and beta-carotene (a provitamin) are termed antioxidant vitamins because they inactivate oxygen free radicals.
    维生素 C、E 和 β-胡萝卜素(维生素原)被称为抗氧化维生素,因为它们可以灭活氧自由基。
  1. The sources, functions, and related deficiency disorders of the principal vitamins.
    主要维生素的来源、功能和相关缺乏症。
  2. Most physicians do not recommend taking vitamin or mineral supplements except in special circumstances, and instead suggest being sure to eat a balanced diet that includes a variety of food.
    除特殊情况外,大多数医生不建议服用维生素或矿物质补充剂,而是建议确保均衡饮食,包括多种食物。

  1. DISORDERS: HOMEOSTATIC IMBALANCES
    疾病:体内平衡失衡

  1. Fever is an elevation of body temperature that is due to resetting of the hypothalamic thermostat. The most common cause of fever is a viral or bacterial infection.
    发烧是由于下丘脑恒温器重置导致的体温升高。发烧最常见的原因是病毒或细菌感染。
  2. Obesity is defined as a body weight more than 20% above desirable standard as the result of excessive accumulation of fat.
    肥胖被定义为由于脂肪过度积累而导致体重超出理想标准20%以上。
  1. Even moderate obesity is hazardous to health.
    即使是中度肥胖也会危害健康。
  2. Obesity is implicated as a risk factor in cardiovascular disease, hypertension, pulmonary disease, non-insulin dependent diabetes mellitus (type II), arthritis, certain cancers (breast, uterus, and colon), varicose veins, and gallbladder disease.
    肥胖是心血管疾病、高血压、肺部疾病、非胰岛素依赖型糖尿病(II 型)、关节炎、某些癌症(乳腺癌、子宫癌和结肠癌)、静脉曲张和胆囊疾病的危险因素。