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Gas exchange and respiration



           Alternatively, in the lactate  fermentation,  2 ATP  molecules are produced for every
           molecule of glucose used.

           Glucose             2Lactate + 2ATP

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           The amount of energy contained in 2 ATP molecules is 2 x 30.6 = 61.2 kJ.

           The total energy released during the conversion of glucose into lactate is 150 kJ per
           mole. Thus, the efficiency of energy transfer during lactate fermentation is 61.2/150 x
           100% = 40.8%.


           The total energy released when glucose molecule is respired aerobically is 38 ATP, but
           the total energy released in anaerobic respiration of glucose is only 2ATP. Therefore,
           aerobic respiration is more efficient than anaerobic respiration.


           Table 6.4 : Amount of ATP produced from glucose respired anaerobically
               Respiratory        Number of     Number       ATP direct     Total number of
               process             NADH         of FADH       formed         ATP molecules


               Glycolysis: glucose
               to pyruvate              2            -             2                2

           6.3.4 Respiratory pathway using lipids     can be converted into glucose and follow
           and protein                                the patterns in glycolysis to the electron
           Lipids  and proteins  are  respiratory  transport  chain.  The  fatty  acids  join  the
           substrates in addition to carbohydrates,  Kreb’s cycle as fatty acid fragments, each
           which are used by most cells.  The  with 2 carbons that are joined with Acetyl
           respiratory pathways for both aerobic  CoA.  The fatty  acid  will make  several
           and anaerobic process involve the stages  Kreb’s cycles depending on the number of
           of respiration such as glycolysis, the  fragments formed. The products of Kreb’s
           Kreb’s cycle, and electron transport chain.  cycles  will  add  up in  generating  a  huge
           Aerobes use them all, whereas anaerobes  amount of ATP from lipids.
           use only glycolysis.  Lipids and proteins
           are not directly accommodated in these  Proteins are polymers of amino acids.
           pathways, they are converted or changed  Amino acids have amino and carboxylic
           to suit the type of the metabolites required  groups. They also have a varied number of
           by such pathways (Figure 6.15).            carbon  atoms.  Being  polymers,  proteins
                                                      should be hydrolysed into amino  acids
           Lipids  are  polymers  of fatty  acids  and  which  are  deaminated  to  remove  the
           glycerol.  They  have  to  be  hydrolysed  amino  groups.  The remaining  portions
           into  glycerol  and  fatty  acids.  Glycerol  enter  the respiratory  pathway  depending



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