catabolism, anabolism點解呀,爆急

Catabolism is the metabolic process that breaks down molecules into smaller units. It is made up of degradative chemical reactions in the living cell. Large polymeric molecules (polysaccharides, nucleic acids and proteins) are processed into their constituent monomeric units (i.e. monosaccharides, nucleotides and amino acids, respectively).

Cells use monomers to construct new polymeric molecules and disassemble them to simple cellular metabolites (lactic acid, acetic acid, carbon dioxide, ammonia, urea, etc.). The creation of cellular metabolites is an oxidation process involving a release of chemical free energy, not all of which is lost as heat, but some of which is partially conserved through the coupled synthesis of adenosine triphosphate. The hydrolysis of this compound is subsequently used to drive almost every energy-requiring reaction in the cell. Catabolism provides the chemical energy necessary for the maintenance of the living cell. Examples of catabolic processes include breakdown of muscle protein in order to use amino acids as substrates for gluconeogenesis and breakdown of fat in adipose to fatty acids.

Because it is counterproductive to have anabolic and catabolic processes occurring in cells simultaneously, there are many signals that switch on anabolic processes while switching off catabolic processes and vice versa. Most of the known signals are hormones and the molecules involved in metabolism itself. Endocrinologists have traditionally classified many of the hormones as anabolic or catabolic.


Anabolism is the metabolic process that builds larger molecules from smaller ones. One way of categorizing metabolic processes, whether at the cellular, organ or organism level is as 'anabolic' or 'catabolic', which is the opposite.

Anabolic processes tend toward "building up" organs and tissues. These processes produce growth and differentiation of cells and increase in body size, a process that involves synthesis of complex molecules. Examples of anabolic processes include growth and mineralization of bone and increase of muscle mass.

Because it is counterproductive to have anabolic and catabolic processes occurring in cells simultaneously, there are many signals that switch on anabolic processes while switching off catabolic processes and vice versa. Most of the known signals are hormones and the molecules involved in metabolism itself. Endocrinologists have traditionally classified many of the hormones as anabolic or catabolic.

2006-11-02 01:59:13 補充：
Anabolism =異化作用就是生物的分解代謝。是生物體將體內的大分子轉化為小分子並釋放出能量的過程。呼吸作用是異化作用中重要的過程。根據生物的呼吸作用是否需要氧氣，可將生物分為需氧生物、厭氧生物和兼性生物。

2006-11-02 01:59:29 補充：
異化作用的實質是生物體內的大分子，包括蛋白質、脂類和糖類被氧化併在氧化過程中放出能量。能量中的部分為ADP轉化為ATP的反應吸收，並由ATP作為儲能物質供其他需要。有氧的異化作用中，糖、脂類、蛋白質等變為含羧基的化合物併進行了脫羧的酶促反應，生成二氧化碳；而氫則由脫氫酶激活在線粒體內經過呼吸鏈的傳遞將底物還原逐步釋放能量，自身被氧化生成水。無氧的異化作用缺乏氧這一氧化劑，不能完全將大分子分解，釋放出其中的能量。

catabolism (kətăb'əlĭz'əm) , subdivision of metabolism involving all degradative chemical reactions in the living cell. Large polymeric molecules such as polysaccharides, nucleic acids, and proteins are first split into their constituent monomeric units, such as amino acids, after which the monomers themselves can be broken down into such simple cellular metabolites as lactic acid, acetic acid, carbon dioxide, ammonia, and urea. The first set of reactions provides the cell with monomers with which it can construct new polymeric molecules. The second set of reactions usually involves the process of oxidation and is accompanied by a release of chemical free energy, not all of which is lost as heat, but is partially conserved through the coupled synthesis of adenosine triphosphate. The hydrolysis of this compound is subsequently used to drive almost every energy-requiring reaction in the cell. Thus catabolism also provides the source of chemical energy necessary for the maintenance of the living cell.



Anabolism is the metabolic process that builds larger molecules from smaller ones. One way of categorizing metabolic processes, whether at the cellular, organ or organism level is as 'anabolic' or 'catabolic', which is the opposite.

Anabolic processes tend toward "building up" organs and tissues. These processes produce growth and differentiation of cells and increase in body size, a process that involves synthesis of complex molecules. Examples of anabolic processes include growth and mineralization of bone and increase of muscle mass.

Because it is counterproductive to have anabolic and catabolic processes occurring in cells simultaneously, there are many signals that switch on anabolic processes while switching off catabolic processes and vice versa. Most of the known signals are hormones and the molecules involved in metabolism itself. Endocrinologists have traditionally classified many of the hormones as anabolic or catabolic.

catabolism: complex molecules are broken down into simpler molecules
anabolism: simpler molecules are built up to form complex ones.
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