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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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