16_Metabolism - XVI Metabolliism XVI Metabo sm 0B All...

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0 B X X X V V V I I I . . . M M M e e e t t t a a a b b b o o o l l l i i i s s s m m m All cellular functions depend on chemical reactions. These reactions are organized into sequences (metabolic pathways) designed for specific purposes. The two main pathways are (i) catabolism, in which substances are broken down, and (ii) anabolism, in which substances are synthesized. Examples of the two pathways are, respectively: respiration: 2 n 2 2 2 (CH O) + O H O + CO photosynthesis: 2 2 2 n 2 H O + CO (CH O) + O The end products of each pathway are diverse, but the pathways have one thing in common: energy transformations. 1 B T T T h h h e e e r r r m m m o o o d d d y y y n n n a a a m m m i i i c c c s s s : : : t t t h h h e e e s s s c c c i i i e e e n n n c c c e e e o o o f f f e e e n n n e e e r r r g g g y y y Energy is simply the capacity to do work. 2 B K K K i i i n n n e e e t t t i i i c c c a a a n n n d d d p p p o o o t t t e e e n n n t t t i i i a a a l l l e e e n n n e e e r r r g g g y y y There are many forms of energy: Kinetic energy is contained in moving objects; examples on a molecular scale include the energy of vibrations, random diffusion, and heat. Potential energy is stored in position, molecular bonds, etc. 3 B L L L a a a w w w s s s o o o f f f t t t h h h e e e r r r m m m o o o d d d y y y n n n a a a m m m i i i c c c s s s Transformations from one form of energy to another are governed by three laws of thermodynamics. 7 B I I I s s s t t t L L L a a a w w w Total energy is constant. Energy can be transformed from one form to another, but it can't be destroyed or created.
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