Chapter 22, Problem 1P

Summary Introduction

To determine: Bacteria forms colony inside the root nodules of the pea plant and consume 20% of the $\text{ATP}$ produced by the plants, the reason for this much consumption by the bacteria.

Introduction:

Nitrogen is the essential nutrient for plants. Legumes use “nitrogen fixing bacteria”, within their root nodules to counter the limitation. Rhizobia is a nitrogen fixing bacteria that produces ammonia. These bacterial are called as “nitrogen-fixing bacteria”.

Explanation of Solution

Explanation:

Root nodules contain bacteria maintain a “symbiotic relationship” with the pea plant where the plant supplies the bacteria with ATP and reducing power. The bacteria in return supply the plant with “ammonium ions” produced by reducing atmospheric nitrogen as plants cannot use nitrogen in its molecular form.

The reduction of nitrogen to ammonium ions requires large amount of energy in the form of ATP. The triple bond of nitrogen is very stable. Therefore, fixation of nitrogen exhibits very high activation energy, as atmospheric nitrogen is chemically non-reactive or inert under normal conditions.

This high activation energy barrier is overcome by the hydrolysis of ATP.

${\text{N2+10H}}^{\text{+}}{\text{+8e}}^{\text{-}}\text{+16ATP}\to {\text{2NH4}}^{\text{+}}\text{+16ADP+16Pi+H2}$

Conclusion

Conclusion:

Root nodules are type of symbiotic association between plant and bacteria and with the help of this processes both are benefited.