. Principles of modern biology. Biology. CERTAIN AMINO ACID, PROLINE, ARGININE, etc. OTHER AMINO ACIDS, TYROSINE, ASPARTIC, etc. ACETYL - CoA. KREBS (CITRIC ACID) CYCLE Fig. 8-13. Some major pathways of cellular metabolism. Schematic summary, after Krebs. reactions, in reverse, can lead to synthesis, provided that a proper source of energy and precursory substances are on hand. The pat- terns of metabolism provide considerable facility for the interconversion of substrates —proteins into carbohydrates, carbohydrates into fats, and so forth. This is possible be- cause the pathways of
. Principles of modern biology. Biology. CERTAIN AMINO ACID, PROLINE, ARGININE, etc. OTHER AMINO ACIDS, TYROSINE, ASPARTIC, etc. ACETYL - CoA. KREBS (CITRIC ACID) CYCLE Fig. 8-13. Some major pathways of cellular metabolism. Schematic summary, after Krebs. reactions, in reverse, can lead to synthesis, provided that a proper source of energy and precursory substances are on hand. The pat- terns of metabolism provide considerable facility for the interconversion of substrates —proteins into carbohydrates, carbohydrates into fats, and so forth. This is possible be- cause the pathways of protein, carbohydrate, and fat metabolism join each other at a com- mon cross road, provided by acetyl coenzyme A (Fig. 8-5). By reverse pathways material derived from one source (for example, pro- tein) may be diverted into another (for ex- ample, carbohydrate), in such a manner that the cell has great flexibility in its utilization of different organic molecules. TEST QUESTIONS 1. What important compounds are represented by the following symbols: ATP. ADP, and AMP? Specify the number (if any) of high- energy phosphate bonds that are present in each case. 2. How do high-energy phosphate bonds differ from ordinary phosphate linkages? What symbols are used to distinguish between the two types? 3. What type of chemical reaction is represented by the splitting of high-energy phosphate bonds? Give one such reaction. 4. Specify five different types of cellular ac- tivity that derive energy from the hydrolysis of ATP. What other cellular processes may be energized by ATP? 5. To what extent is it true that many catabolic reactions contribute energy toward main- taining the ATP reserves of the cell? Ex- plain. 6. Differentiate between oxidation and reduc- tion: a. in terms of die transfer of electrons b. in terms of hydrogen transfer 7. Provide an example to illustrate the fact that oxidations and reductions are insepara- ble, mutually dependent processes. 8. Under what circumstances
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