Subcellular Systems - Molecular Theory of the Living Cell - page 378

Scheme ( 11.56 ) is known to be reversible so that protons can be pumped across the
mitochondrial inner membrane (producing osmotic energy) driven by the chemi-
cal energy of ATP hydrolysis. On the phenomenological level, therefore, the
concept of chemiosmotic coupling proposed by Mitchell may appear validated
since chemical and osmotic energies are indeed interconverted. But this way of
looking at the problem is superficial. The heart of the problem concerns not so
much whether or not the process of chemiosmosis occurs in mitochondria (which
was known to take place in living systems long before 1961 when the chemios-
motic hypothesis was formulated) but exactly how such a process occurs on the
molecular level. In other words, we must distinguish between the phenomenon of
chemiosmosis and the molecular mechanisms underlying the phenomenon. On the
phenomenological level, the Mitchell hypothesis cannot be faulted. But it is on the
level of molecular mechanisms of chemiosmosis that the Mitchell hypothesis fails
as I have been pointing out over the past three decades (Ji 1979, pp. 34-35; Ji
1991, pp. 60-61; Williams 1969).
Any mechanical (i.e., conformational) energy stored in biopolymers can be
viewed as examples of conformons . Therefore we can rewrite Scheme ( 11.56 )as
follows:

1

ð Proton Gradient Þ> ð Conformons Stored in the g and e Subunits Þ

# 2
Conformons StoredinF 1 $ Chemical Energy of ATP Þ

(11.57)

ð

Process 1 above is the step where conformons are generated from proton
gradients, most likely by reversing the molecular steps postulated for the
conformon-driven active transport described in Fig. 2 in Ji (1979) or Fig. 8.1
in this topic. Process 2 involves conformon transfer from F 0 to F 1 through the
g and e subunits, which probably occurs through the mechanism of conformon
transfer proposed in Fig. 4 in Ji (1974b).

All the problems encountered by the chemiosmotic hypothesis as indicated
above can be resolved simply by invoking the concept of conformons which can
drive either active transport or ATP synthesis as indicated in Fig. 11.36 , depending
on the metabolic needs of the cell. The conformon theory of molecular machines
accounts for not only membrane-dependent oxidative phosphorylation and active
transport but also membrane-independent processes such as muscle contraction
and DNA transcription and replication by RNA and DNA polymerases, respec-
tively, DNA supercoiling, and cytoplasmic molecular motor movements - all
through the common agency of the energy and information carried by conformons
(Ji 1974b, 1979, 2000, 2004a). Thus the conformon concept provides a bioenergetic
mechanism that can be applied universally to all energy-coupled processes in living
systems, including chemiosmosis, but the chemiosmotic approach is limited to
explaining membrane-dependent energy-coupled processes such as proton
gradient-driven ATP synthesis - all on the phenomenological level.