The document discusses nitrogen fixation, a process where atmospheric nitrogen is converted into ammonium ions (NH4+) by certain bacteria, including those in the Rhizobium family found in leguminous plants. It details the role of the nitrogenase complex, composed of reductase and nitrogenase proteins, in this biochemical process under ordinary conditions. Recent studies on the electron transfer mechanisms within these bacteria highlight their potential for efficient nitrogen fixation, as traditional chemical methods are becoming increasingly costly.

1. CECH-612
UNIT-4(A)
BY - Ms MAYURI R SOMPURA

2. • The nitrogen atoms containing biomolecules such as amino acids,
pyrimidines etc come from NH4+ which in turn come from
atmospheric nitrogen by its biochemical reduction.
• The process of conversion of atmospheric nitrogen into NH4+
ions is known as fixation of nitrogen.
• Biological fixation of nitrogen is carried out by blue green algae
viz a family of bacteria is known as rhizhobium bacteria.
• These bacteria invades the roots of leguminous plants such as
peas, beans, alfafa etc and form root nodules in which nitrogen
fixation takes place.
BY - Ms MAYURI R SOMPURA

3. BY - Ms MAYURI R SOMPURA

4. • The bond energy of N=N bond is quite high (950 KJ/mol), The
nitrogen is highly receptable to electronical attack.
• This is why chemical process of nitrogen fixation (viz. haber
process) takes place at high pressure and temperature.
• The biological process of nitrogen fixation, through less efficient,
takes place under ordinary conditions of pressure and temperature.
• The enzyme present in the nitrogen fixing bacteria is the
nitrogenase complex, which is infact family of enzymes varying
slightly from one bacterial species to another in which they are
present.
BY - Ms MAYURI R SOMPURA

5. • The nitrogenase complex is composed of two kinds of protein
components :
• one kind of component is known as reductase.
• Other kind of component is known as nitrogenase.
• The reductase supplies electrons which are used by the
nitrogenase to NH4+.
• The reductase is an Fe-S protein while the nitrogenase is an Fe-
Mo-S protein.
• The stoichiometry of the reaction catalyzed by the nitrogenase
complex is:
N2 + 6 e- + 12 ATP → 2 NH4+ + 12 ADP + 4H+
BY - Ms MAYURI R SOMPURA

6. • RECENT STUDIES SUGGEST FOLLOWING SEQUENCE :-
1. The reduced ferridoxine ( which is the real source of electrons
in the reactive given above ) transferases its electrons to the
reductase component of the nitrogenase complex.
2. ATP then binds to the reductase and thereby alters its
conformation in such a way that it causes a shift in thr
reduction potential of the reductase from 0.30 V- 0.40 V.
The greater the magnitude of the negative value of the reduction
potential.
The greater its tendency to loose electrons and hence the greater is
the reducing power of reductase.
BY - Ms MAYURI R SOMPURA

7. • RECENT STUDIES SUGGEST FOLLOWING SEQUENCE :-
3. The increased reducing power of reductase enables it to transfer
its electrons to the nitrogenase component of the nitrogenase
complex which contains the bound nitrogen.
4. The ATP then gets hydrolysed and the nitrogen bound to the
nitrogenase component gets reduced to NH4+.
Since the source of energy required for the chemical fixation of
nitrogen to ammonia are becoming more and more costly, efforts
are being made by bioscientists to carry out nitrogen fixation by
microorganisms.
BY - Ms MAYURI R SOMPURA