Biology Reference
In-Depth Information
above (see Eq.
8.6
). In other words, energy and force are causally related, leading to
the following dictum:
Without energy no force can be generated; without force no energy can be stored.
(8.13)
For convenience, we may refer to Statement 8.13 as
the molecularized Second
Law of Newtonian mechanics
(MSLNM), in analogy to the
molecularized Second
Law of Thermodynamics
(MSLT) formulated by McClare (1971) and discussed in
Sect.
2.1.4
.
Since the key theoretical principle underlying the
chemical-to-mechanical
energy conversion
mechanism described below is the generalized Franck-Condon
referred to as the
GFCP-based mechanism of conformon production
. GFCP is in
turn related to (and consistent with) two other laws - MSLNM, that is, Statement
among the three theoretical entities implicated in the mechanism of the
chemical-
to-mechanical energy conversion
to be presented.
GFCP
¼
MSLT
þ
MSLNM
(8.14)
The GFCP-based mechanism of conformon generation occurs through the fol-
lowing three key steps:
1.
ETC
(or any molecular machines) can exist in two conformational states - the
ground state (to be denoted as
ETC
and visualized as a relaxed spring in
Fig.
8.1a
) and the thermally activated or excited state (denoted as
ETC
{
and
visualized as a cocked spring in Fig.
8.1b
). These two states are in thermal
equilibrium, which can be represented as
ETC
ETC
{
. Due to the
constraints of the molecularized Second Law of thermodynamics discussed in
<
---
>
t
, the turnover time of
ETC
.
2. In the ground-state
ETC
, the two substrate-binding sites are thought to be
located too far apart for AH
2
to react with B or for the electrons to be transferred
from AH
2
to B. In other words, AH
2
and B are prevented from reacting with each
other in the ground state.
3. When the two sites on
ETC
that bind AH
2
and B are brought close together as a
result of thermal fluctuations of
ETC
(see
a
--
b
in Fig.
8.1
), two electrons are
postulated to be transferred fromA to B (through
quantummechanical tunneling
in
one or more elementary steps), resulting in the formation of two protons in the
AH
2
-binding site and two hydroxyl groups in the B-binding site (see
c
), which
stabilizes
ETC
{
to produce the energized state,
ETC
*. Due to the exergonic nature
of the redox reaction catalyzed by
ETC
,thelifetimeof
ETC
*isnolonger
constrained by the Second Law of thermodynamics and can be much longer than
>
t
.
The intramembrane electron transfer reaction involved in Fig.
8.1
can be
described in greater detail as shown in Fig.
8.2
, taking into account both the
