Key Features of Living Things
Splitting and reforming water molecules
Electron transport chains
Cells and Membranes
DNA and RNA - reproduction and heredity
Water the Hub of Life - How water is critical to life on Planet Water
Extracts from Key Authors Writing about Water and Life
Water is the Stuff of Life
Water is the driver of Nature.
- Leonardo da Vinci
Two prominent scientists have elegantly stated how life on Planet Water is critically
dependent on liquid water. The life as we know it is water-based and water dependent life.
Extracts from Albert Szent-Gyorgyi 1893-1986. "The living state with Observations on
cancer" New York Academic Press 1972
Water is the Hub of Life.
Life originated in the ocean.
Water is its mater
, mother and medium.
Life could leave the ocean when it learnt to grow a skin and take the water with it.
We are still water animals, only we have the water inside, not outside.
We are walking aquarium. We are 20% aqueous solution.
We have guarded our legacy, the water of the sea, carefully.
The ionic concentration of our blood still reflect the ionic concentrations of the
primordial oceans.... Life, having originated in the ocean, could build its machinery
only from what it found there.
It found three things: water, organic molecules (including C02), and ions.
Life’s machinery is built or organic matter using water as its medium.
Life is water dancing to the tune of solids…….
Water structure are just as much part of the living machinery as its organic and more
solid parts. The solid (proteins and lipids) induces and stabilizes the water structure;
the water structure depolarizes, protects, separates, or links sold structures’ and
induces the three-dimensions shape, which is so critical for their function.
……water also plays a central role in energetics.
The driving force of life is the energy of solar radiation which is conserved by being
used to separate the elements of water, H and O, or by taking a water molecule from
between two phosphate molecules.
The energy thus used in the structure can be utilized by reversing these processes and
allowing H and O to unite again (biological oxidation, respiration) or by putting the
water molecule back between the phosphates (hydrolysis of -P, the high energy phosphate
bonds). Bioenergetics is but a special aspect of water chemistry
Whatever we study in biochemistry we find that water plays an essential role, not only
as H2O but also in its ionic state (H+ and OH-). Life processes also involve to a great
extent, a shift of electrons, which must be accompanied by a flow of proton, H+, to
maintain electoneutrality. The protons possibly move in the structured water surrounding
the protein particles.
Extracts from WHAT IS LIFE? by Erwin Shrödinger First published in 1944
LIVING MATTER EVADES THE DECAY TO EQUILIBRIUM
What is the characteristic feature of life? When is a piece of matter said to be alive?
When it goes on 'doing something', moving, exchanging material with its environment, and so
forth, and that for a much longer period than we would expect an inanimate piece of matter
to 'keep going' under similar circumstances.
When a system that is not alive is isolated or placed in a uniform environment, all motion
usually comes to a standstill very soon as a result of various kinds of friction;
differences of electric or chemical potential are equalized, substances which tend to form
a chemical compound do so, temperature becomes uniform by heat conduction.
After that the whole system fades away into a dead, inert lump of matter.
A permanent state is reached, in which no observable events occur.
The physicist calls this the state of thermodynamical equilibrium, or of 'maximum entropy'.
Practically, a state of this kind is usually reached very rapidly. Theoretically, it is
very often not yet an absolute equilibrium, not yet the true maximum of entropy.
But then the final approach to equilibrium is very slow. It could take anything between
hours, years, centuries,...
To give an example - one in which the approach is still fairly rapid: if a glass filled
with pure water and a second one filled with sugared water are placed together in a
hermetically closed case at constant temperature, it appears at first that nothing happens,
and the impression of complete equilibrium is created.
But after a day or so it is noticed that the pure water, owing to its higher vapour pressure,
slowly evaporates and condenses on the solution. The latter overflows.
Only after the pure water has totally evaporated has the sugar reached its aim of being
equally distributed among all the liquid water available.
These ultimate slow approaches to equilibrium could never be mistaken for life, and we may
disregard them here. I have referred to them in order to clear myself of a charge of
To paraphrase these concepts - Life therefore appears to be a revolt against the rules of
Nature. Life is a paradox …. The most basic rule of inanimate nature is that it tends toward
equilibrium which is at the maximum of entropy (i.e. disorder) and the minimum of free
energy. Life goes against this trend …..the main characteristic of life is that it tends
to decrease its entropy. (builds and maintains structure and order)
It also tends to increase its free energy. Maximum entropy means complete randomness,
disorder. Life is made possible by order structure, a pattern, which is the opposite of
entropy. This pattern is our chief possession, it was developed over billions of years.
The main aim of our individual existence is its conservation and transmission.”
How does the living organism avoid decay?
The obvious answer is: By eating, drinking, breathing and (in the case of plants)
assimilating. The technical term is metabolism.
What then is that precious something contained in our food which keeps us from death?
That is easily answered. Every process, event, happening - call it what you will; in a word,
everything that is going on in Nature means an increase of the entropy of the part of the
world where it is going on. Thus a living organism continually increases its entropy - or,
as you may say, produces positive entropy - and thus tends to approach the dangerous state
of maximum entropy, which is death. It can only keep aloof from it, i.e. alive, by
continually drawing from its environment negative entropy.What an organism feeds upon is
We heterotrophs feed on negative entropy by extracting the energy built into the structure
of organic molecules by the auotrophs, such as plants that use solar energy to build
structure into organic molecules such as sugar i.e. the extremely well-ordered state of
matter in more or less complicated organic compounds, which serve them as foodstuffs.
Plants can still make use of it. Plants use the most powerful supply of ‘negative entropy’
WHAT IS ENTROPY?
Let me first emphasize that it is not a hazy concept or idea, but a measurable physical
quantity just like the length of a rod, the temperature at any point of a body, the heat
of fusion of a given crystal or the specific heat of any given substance.
At the absolute zero point of temperature (roughly- 273°C) the entropy of any substance is
zero. When you bring the substance into any other state by slow, reversible little steps
(even if thereby the substance changes its physical or chemical nature or splits up into
two or more parts of different physical or chemical nature) the entropy increases by an
amount which is computed by dividing every little portion of heat you had to supply in
that procedure by the absolute temperature at which it was supplied - and by summing up
all these small contributions.
To give an example, when you melt a solid, its entropy increases by the amount of the heat
of fusion divided by the temperature at the melting-point.
You see from this, that the unit in which entropy is measured is cal./°C
(just as the calorie is the unit of heat or the centimetre the unit of length).
However it has been pointed out to me that my simple thermodynamical considerations cannot
account for our having to feed on matter 'in the extremely well ordered state of more or
less complicated organic compounds' rather than on charcoal or diamond pulp.
This is correct. But to the lay reader I must explain that a piece of un-burnt coal or
diamond, together with the amount of oxygen needed for its combustion, is also in an
extremely well ordered state, as the physicist understands it. Witness to this: if you
allow the reaction, the burning of the coal, to take place, a great amount of heat is
produced. By giving it off to the surroundings, the system disposes of the very
considerable entropy increase entailed by the reaction, and reaches a state in which it has,
in point of fact, roughly the same entropy as before.
Yet we could not feed on the carbon dioxide that results from the reaction.
And so the energy content of our food does matter.
Energy is needed to replace not only the mechanical energy of our bodily exertions,
but also the heat we continually give off to the environment.
And that we give off heat is not accidental, but essential.
For this is precisely the manner in which we dispose of the surplus entropy we
continually produce in our physical life process.
How does water support Life
The physical and chemical properties of water are the foundation for life.
See Chemical Properties of Water >>
See Physical Properties of Water >>
Water readily dissolves most salts. However, water is a poor solvent for proteins and
lipids and other large organic molecules in living cells.
This means that liquid water can transport nutrient elements to and within living cells
without dissolving and destroying the organic molecules of which cells are made.
Water also transports waste elements away from cells.
Thus, all living cells contain water, with the proportion ranging from 3-5% in
resting seeds to perhaps 95% in very young plant tissues and jellyfish.
This water penetrates the cell protoplasm, but does not dissolve it.
Increased water content leads to increased chemical activity within the cell.
Without water, there would be no life.
Role of water on Planet Water
Only the planet Earth has three states of water on its surface, and it offers a suitable
environment for life to begin, among all nine solar planets. Since all life forms involve
Water is extremely important as a modifier of climate. It stores heat in great quantities,
transports it around the globe, both in ocean currents and in atmospheric vapour,
and helps to retain stored at the earth's surface by reducing its radiative loss to space.
As an effective solvent, and as a physical mass releasing energy as it moves downhill,
water is a major modifier of the earth's surface.
It erodes and breaks down rock, carries materials downstream, and deposits these
eroded mineral particles in depressions where they can combine with organic materials
to form . It can also erode these soils, leaving a greatly altered landscape.
The very nature of our planet's surface is a product of water and its distribution.
Of course, the very ability of water to run downhill and shape the earth's surface is
dependent on a process known as the water cycle or hydrologic cycle.
In this cycle, heat energy from the sun causes liquid water and ice to evaporate or
sublimate and escape to the atmosphere as vapour.
This vapour is then transported within the atmosphere until such time as changing
conditions cause some of it to precipitate or fall back to the earth's surface as
rain, snow, or dew.
This water, once returned to the surface, can resume its downhill movement until it
reaches the oceans or is vaporized once more.
This process of is extremely important as a means of cleansing water of its dissolved
substances, which are left behind when the water evaporates.
Energy from the sun drives this ecosystem, but all the communities shown, the plants on
shore, and those humans who use this ecosystem, are linked by the common element, water.
Anything affecting the quality or availability of this water will have an impact on the
entire ecosystem. However, ecosystems are complex and our understanding of them is
incomplete. Often, We are not able to predict in advance exactly what that effect might be.
Balancing water in bio-systems
Many living organisms live their lives entirely in water. Aquatic living organisms extract
nutrients from water, yet maintaining a balance of electrolyte and nourishment
concentration in their cells. For living things not living in water, they extract water
from their environment by whatever mechanism they can. Cells in their body are surrounded
by body fluid, and all cells maintain constant concentrations of electrolytes, nutrients,
and metabolites. The process of maintaining constant concentrations is called homeostasis.
Certainly, some active transport mechanisms are involved in this balance.
It is no exaggeration to say that all living things are mainly water and all organisms
including ourselves are great sacks of water.
Each cell in your body is composed of 70-90% water, and as a result you are
approximately 65% water overall.
>> See Next: Carbon >>