This article may be useful as supplementary reading for biology classes, based on the DSE syllabus.
根據生物科文憑試課程剛要，本文或可作為有用的補充讀物。
Staggering
population growth
and industrialisation in the past century have led
to a tremendous increase in energy expenditure,
resulting in a series of energy crises and irreversible
environmental repercussions. To address these
growing energy demands, much focus has been
placed on developing technology that can
harness renewable energy sources. Scientists are
now closer than ever to constructing a system with
the ability to transform water into fuel using solar
energy, which may just hold the key to offsetting
carbon emissions and quenching our thirst for
energy. For example, an artificial leaf that is able to
carry out photosynthesis is one of such projects.
So l a r ene rgy i s an unex p l o r ed nat u ra l
resource largely untapped until recently. Current
solar photovoltaic cell technology possesses
crippling limitations that prevent widespread
commercialisation, including low efficiency and
intermittency. Plants, on the other hand, have been
harnessing energy from the sun for billions of years,
using sunlight to produce usable glucose from
carbon dioxide and water in a well-known process
called photosynthesis. Artificial photosynthesis that
mimics this clever natural process can theoretically
create a storable supply of energy and electricity.
Instead of glucose, however, the desired end
product is liquid hydrogen to be used as fuel
that is stored in a fuel cell. This can be achieved
by splitting water molecules for the isolation of
hydrogen.
By integrating biology and nanoscience,
researchers at the University of California at
Berkeley, have discovered a novel approach
to water-splitting and carbon fixation, utilising
a common bacter ium as the biocatalyst [1].
Photosynthesis is comprised of two major steps:
the photochemical reactions and the l ight-
independent carbon fixation. In most autotrophs
(organisms that are capable of producing their
own food using surrounding inorganic materials),
light is absorbed by chlorophyll in the photosystems
of chloroplasts and water is broken down into
hydrogen ions, oxygen ions and electrons. The
released electrons have multiple functions. It can
be used to reduce the photo-oxidised chlorophyll.
Alternatively, it can move along the electron
transport chain and gradually release energy in
the process by reducing NADP+ into NADPH to
produce sugar by fixing CO
2
molecules in the light-
independent reactions.
Artificial photosynthesis manipulates natural
photosynthesis in a way that biochemical reactions
will harness and store solar energy in the chemical
bonds by i ntercept i ng e l ect rons produced
i n the photos ys tems . Th i s method emp l oys
photosynthesisers such as chlorophyll in solar cells.
Recently, researchers at Massachusetts Institute of
By David Iu
姚誠鵠
