Photosynthesis and Respiration
can probably balance out the gases
necessary for life even in a small,
sealed glass
container floating in outer space*.
*as long as it is kept from freezing.
Humans are falible.
^l
Biosphere 2
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Biosphere 2 was our attempt to design an ecosystem completely independent of
Earth and live in it.
It failed because the people ran low on breathable oxygen.
This proves that Biosphere 1 (Earth) is a complex system that we cannot yet
duplicate perfectly.
Let's attempt to understand why.
First some background info: Chemystery.
Elements of Life: (Earth, Air, Water)
H - Hydrogen
O - Oxygen
“Organic”
C - Carbon
elements form
N - Nitrogen
covalent bonds.
P - Phosphorus
S - Sulfur
Ca - Calcium
Na - Sodium
K - Potassium
Charged Ions
Cl – Chloride
or salts
Mg – Magnesium
Fe - Iron
and other trace elements...
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Energy for life: (Fire)
Sunshine measured in joules or calories.
The greeks believed all
matter is composed of 4
elements: earth, air,
water and fire.
They weren't too far off,
but the first three
elements are composed
of ~92 chemical
elements from stardust.
The fire element
represents the energy
contained in the bonds
between the elements.
Atoms have two different strategies to
deal with an incomplete set of electrons.
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Atoms may give or take an
electron or two and
become positive (electron
poor) or negative (electron
rich) ions.
Atoms may share
electrons in covalent
bonds.
Polar bonds are covalent
bonds that have some
characteristics of ionic
bonds.
Biochemicals are
composed of covalent
bonds.
What is a Calorie?
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1000 calories = 1 food Calorie
(kilocalorie)
1 calorie = 4.18 joules
A 100 watt light bulb uses 100
joules per second, or ___
Calories per second.
? Calories/ second ?
How long does it take the light bulb to
burn a Calorie (kcal)?
Chemical reactions may store or
release energy.
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Covalent bonds form when two
atoms have a lower energy state
when they are together, rather
when they are apart.
Each type of covalent bond stores
a different amount of energy.
The process by which covalent
bonds form and break is called a
chemical reaction.
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Reactants ---> Products
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Bonds broken ----> Bonds formed
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If there is energy released during a
chemical reaction, it is because the
bonds formed have a lower energy
state than the bonds broken.
Respiration and Photosynthesis are
the basic chemical reactions of life.
Photosynthesis: light from the sun +
CO2 + H2O ----> CH2O + O2
Respiration:
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CH2O + O2 ----> CO2 + H2O
+ cellular energy and/or heat
During photosynthesis plants store energy from the sun in
the bonds of carbohydrates.
Energy stored in the chemical bonds of carbohydrates is
released during respiration and used to do work in living
cells.
Q: How much energy is released
during respiration?
Respiration:
CH2O + O2 ----> CO2 + H2O
+ cellular energy and/or heat
C-H bond: 99 kcal / mole
C=O bond: 180 kcal/mole
O=O bond: 119 kcal/mole
O-H bond: 111 kcal/mole
Breaking bonds requires energy, forming bonds releases energy.
1 mole = 6.02 x 1023 atoms or molecules.
1 mole of hydrogen with an atomic mass of one is equal to one gram.
Q: How long could 1 mole of CH2O
(about 30 grams of sugar, or one softdrink) power our 100 watt light bulb?
Plants are made mostly of air!
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CH2O and O2
CO2, H2O, NO3-,
PO43-, minerals,
And other nutrients
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Plants create
carbohydrates (sugar,
wood) from carbon
dioxide and water.
Carbon dioxide is a
trace gas in air.
This gas is a nutrient
for plants.
Other organic
elements are also
nutrients for plants.
Nutrients feed plants which manufacture the
building blocks of life.
Nutrient
Carbon
dioxide gas
from air
Nitrate in
water and
soil
Phosphates
in water and
soil
(CO2)
(NO3-)
(PO43-)
Cellular
“machine”
Carbohydrates Proteins
(CH2O) and
fats (CnH2n + 2)
DNA, RNA
Cellular
function
Energy
storage
“blueprint”
for making
proteins
Structure,
transport,
locomotion
Plants and animals recycle each others
waste products in the presence of
sunshine.
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Photosynthesis
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Respiration
Animals respire.
Plants photosynthesize
(and respire too).
Sunshine is required to
fuel the plants that feed
the animals.
Animals inhale oxygen
which plants release,
and plants take up
carbon dioxide which
animals exhale.
Ecosystems are living networks in which
the only waste product is low-grade heat.
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Nutrients are constantly
recycled as long as there
is energy from sunshine.
When there is an
accumulation of wastes, an
organism will invade or
evolve to use the excess
waste.
Ecosystems are living networks in which
the only waste product is low-grade heat.
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Nutrients are constantly
recycled as long as there
is energy from sunshine.
When there is an
accumulation of wastes, an
organism will invade or
evolve to use the excess
waste.
The first pollution on Earth was
eventually used by other organisms.
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1 billion years ago, the Earth
was anaerobic (had no oxygen
gas - O2).
Carbohydrates were created
with a primitive photosynthesis
that did not involve oxygen, and
anaerobic life used fermentation
to get energy from sugars.
Cyanobacteria (blue-green
algae) evolved to produce
oxygen, and poisoned
anaerobic life.
Organisms eventually evolved
to use oxygen (aerobic life).
Respiration evolved because it is
very energetically favorable.
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A fire needs three
things: heat (initial
energy input), fuel
and oxygen.
Respiration is very
similar to combustion.
All that must happen
is to harness the “fire”
and use it to drive
mechanisms in the
body and cells.
Photosynthesis evolved once, it has
been copied many, many times.
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~1000X mag.
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All plants contain
chloroplasts, an organelle
which harvests sunlight.
Chloroplasts store energy
from sunshine in the
chemical bonds of
carbohydrates (sugars).
Cyanobacteria are the
ancestors of all
chloroplasts.
Basically, cyanobacterial
cells are living within all
plant cells! This is an
example of symbiosis.
Respiration also evolved sparingly.
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picture of mitochondria
Mitochondria give energy to the
~1000x
host cell in exchange for protection
magnification
and carbohydrates.
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Respiration evolved to use oxygen.
Mitochondria are organelles in
animals (and plants too) that allow
them to respire carbohydrates and
gain cellular energy.
Mitochondria are also called the
“powerhouse” of the cell.
Mitochondria are descended from a
bacterium that evolved to use
oxygen very efficiently.
Eukaryotic Cells provide protection
and carbohydrate to the
mitochondria, while the
mitochondria provide cellular
energy to the eukaryotic cells.
They can afford this arrangement
because there is SO much energy
in oxygen vs. fermentation.
Eventually respiration balanced
photosynthesis.
Hypothetical concentrations
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O2
21 %
CO2
Levels decreased
(however they are
increasing currently)
Time
(after cyanobacteria evolved)
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Equilibrium is the state in which all
processes are in balance and there
is no accumulation of wastes.
Oxygen is maintained at a fairly
stable 21% in our atmosphere, at
higher concentrations, combustion
proceeds more quickly and
consumes oxygen. This is an
example of a negative feedback –
a process that acts to cancel its
own trigger.
Gaia.
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The earth is a
complex system
which sustains the
conditions necessary
for life.
James Lovelock
pioneered the idea in
1970, and growing
evidence supports his
ideas.
Negative and Positive feedbacks can
influence Earth’s climate in important
ways.
Initial addition of carbon dioxide.
Extra heat could cause more
evaporation.
The added water vapor could trap more
heat.
Or could clouds cause the sun’s rays to
be reflected and cool the surface?
What one is the positive and which one
the negative feedback here?
Can we balance photosynthesis and
respiration in a sealed glass jar?
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You will get your very
own ecosystem in a
glass jar.
How long can it
survive on its own?
What might prevent it
from lasting forever?
We can't yet duplicate Gaia.
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So let’s treat her well…