Geoscience Reference
In-Depth Information
Fig. 11.1
The principle of
photosynthesis: carbon
dioxide + water + light
energy = glucose + oxygen.
The rate of photosynthesis
depends on CO
2
concentration, light intensity,
and temperature. The
chlorophyll molecules are
located on the outside part of
the ring-shaped thylakoids
that form one of the parts of
the chloroplast. In the inside
part of the chloroplast, the
sugars and starch produced
by photosynthesis are kept
and protected by the outer
and inner membrane of the
chloroplast; see the Fig.
11.2
realized by the transformation of ATP to ADP (adenosine diphosphate) by remov-
ing one of the phosphates. Such energy is required for a new plant, for the growth of
roots, or for the development of new hair roots. Without such energy resources,
fl owers cannot exist. Another example of energy use is when stomata openings are
changed, i.e., when work has to be performed. This ubiquitous ATP molecule of
living cells is also used to build complex molecules when it powers virtually every
activity of the cell and organisms. At the same time the neighboring cells next to
stomata cells have to be informed about this change. Such information transferred
by ATP also happens in all instances when a cooperation of cells is required. Without
this transfer, the abovementioned changes of stomata closing and opening are not
achieved. However, this is only a single example of the generally acting information
system. The cycle ATP
ATP is repeated in accordance to the
external situation. If the release of energy by ATP
→
ADP and ADP
→
ADP was not suffi cient, the
“release” of phosphate and energy would continue up to AMP (adenosine mono-
phosphate). Here is the source of energy for active transport of ions and molecules
across plasma membranes and the synthesis of biomolecules.
Three scientists - John Walker, Paul Boyer, and Jens Skou - provided the basis
for a detailed understanding of photosynthesis. They received the Nobel Prize for
Chemistry in 1997 for showing how ATP shuttles energy. Walker started the studies
by determining the amino acid sequence of the enzyme responsible for ATP synthe-
sis and then elaborated its three-dimensional structure. Boyer showed the reality of
ATP enzyme creation in contrast to the previously accepted belief that ATP is
formed from synthesis of ADP and phosphate. Skou showed that this enzyme pro-
moted ion transport through membranes and later proved that the phosphate group
ripped from ATP binds directly to the enzyme.
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