Transcript Energy and Metabolismx

Energy and Metabolism
How living things use energy
Energy Takes Many Forms
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Energy is the ability to make
matter change or move.
Forms of energy include
chemical, mechanical, light,
sound, thermal (heat), and
electrical.
Energy can also exist as
kinetic(causing movement
right now), or potential (stored
for use at a later time).
Energy can change from one
form to another.
Thermodynamics is the study
of energy transformations.
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The first law of
thermodynamics says that
energy is neither created nor
destroyed, it just changes
form.
The second law of
thermodynamics says that
disorder (entropy) in the
universe constantly
increases. Things tend to
become disorganized.
All living things need a
constant supply of energy.
Almost all energy for living
systems comes from the
sun.
Energy Flow Through Living
Systems
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Energy from the sun enters
most living systems by the
process of photosynthesis.
Some bacteria get energy by
the process of
chemosynthesis.
Organisms that harvest
energy either by
photosynthesis or
chemosynthesis are called
autotrophs.
Living things that cannot
harvest energy directly must
eat food to get energy.
These organisms are called
heterotrophs.
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Energy stored in food is
released by the process of
cellular respiration.
The energy in food is stored
in the electrons of C—H
bonds. When these
electrons are transferred to
new bonds, so is the energy!
Chemical reactions that
transfer electrons are called
oxidation-reduction
reactions. Oxidation is the
loss of electrons, and
reduction is the gaining of
electrons.
Energy and Chemical Reactions
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Chemical reactions absorb or
release energy. If the reactants
contain more energy than the
products, energy is released. If
the products contain more
energy than the reactants, then
energy is absorbed.
Energy from chemical reactions
that drives cell activities is called
free energy.
Reactions that release free
energy are called exergonic.
Reactions that absorb free
energy are called endergonic.
Activation energy is the energy
needed to start a chemical
reaction.
Exergonic Reaction
Reactants
Activation Energy
Free
Energy
Released
Endergonic Reaction
Activation
Energy
Products
Free
Energy
Absorbed
Speed of Chemical Reactions
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I.
II.
III.
IV.
In order for living
things to stay alive,
their chemical
reactions must take
place very quickly.
There are four ways to
increase the speed of
a chemical reaction:
Increase the
temperature.
Increase reactant
concentration.
Increase the surface
area of the reactants.
Use a catalyst.
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Cells cannot increase temperature to
speed up their reactions more than a
few degrees, because high
temperatures destroy cell structure.
Cells cannot increase reactant
concentration significantly without
destroying cell structure.
Cells cannot increase the surface
area of their reactants because the
reactants are dissolved in water and
are already individual molecules.
The most efficient way for cells to
make reactions happen fast enough
to maintain life is to use a catalyst.
Enzymes Are Catalysts in Cells
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Any substance that lowers the
activation energy of a reaction
is called a catalyst. In living
systems, enzymes do this.
Like other catalysts, enzymes
are not permanently changed
by the chemical reactions they
catalyze.
The reactant molecule that the
enzyme binds to is called a
substrate. Because of their
shapes, enzymes only bind to
certain substrates.
The part of the enzyme that
binds to the substrate is called
the enzyme’s active site.
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Without enzymes, the chemical
reactions of living things would
happen too slowly to sustain
life.
Enzymes work best at certain
temperatures and certain pH
ranges.
Substrates
Active Site
Enzyme
Energy Flow Through
Ecosystems - Producers
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Autotrophs, which include all
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plants, some protists, and some
bacteria, make their own food from
small inorganic molecules.
 Most producers are photosynthetic,
which means that they use energy 
from the sun to power food
production.
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chemosynthetic. This means that
they use the energy from chemical
bonds in inorganic molecules to
power their food production.
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 These bacteria are found at the
openings of undersea volcanoes 
and form the basis for deep-sea
ecosystems.
In terrestrial ecosystems, plants are
the major producers. In most aquatic
ecosystems protists and
cyanobacteria are the major
producers.
Gross primary productivity
measures how fast producers in an
ecosystem capture energy.
Photosynthetic producers use this
energy for tissue repair, or to make
new organic material by growth or
reproduction.
This new organic material is called
biomass.
The biomass available to other
organisms is called net primary
productivity and measures the health
of an ecosystem.
Comparative Productivity of
Ecosystems
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Net primary productivity varies from one kind of ecosystem to another.
 Although rainforests take up only 5% of the Earth’s surface area, they
account for nearly 30% of the Earth’s net primary productivity from terrestrial
ecosystems.
 Changes in light, precipitation, and temperature are responsible for most of
the differences in productivity among terrestrial ecosystems.
 Changes in light and available nutrients cause productivity differences in
aquatic systems.
Comparative Productivity of Ecosystems
Average net primary
productivity (g/m2/yr)
2000
1500
1000
500
0
Desert
Open Ocean
Temperate Grassland
Lake
Savanna
Estuary
Tropical Rainforest
Energy Flow Through
Ecosystems - Consumers
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All animals, most protists, all fungi,
and many bacteria are
heterotrophs (consumers). They
cannot make their own food, and
so must eat (consume) other
organisms or organic waste.
 Consumers are grouped
according to their main type of
food.
 Herbivores eat producers. Cattle,
deer, grasshoppers, and some
zooplankton in the oceans are
herbivores.
 Carnivores eat other consumers.
Wolves, lions, spiders are
carnivores.
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Omnivores eat both producers and
consumers. Bears and humans are
omnivores.
 Detrivores are consumers that eat
dead organisms or parts of
organisms, or animal wastes. Many
fungi, vultures, and bacteria are
detrivores.
 Decomposers are consumers that
cause decay by breaking down the
large molecules in organic wastes or
dead organisms into small molecules
that can be recycled. Some bacteria,
fungi, and protists are decomposers.
 Decomposers recycle molecules so
new life can grow using those
molecules.
Energy Flow Through
Ecosystems – Energy Flow
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When one organism eats another  Roughly 10 percent of the total
organism, molecules and the
energy consumed in a trophic level is
energy within them are transferred.
available to be passed on to an
This is how energy flows through
organism at the next level of the
the living world.
pyramid.
 One way to study energy flow is to  The other 90 percent of the energy
group organisms into a pyramid
produced or consumed is used to
according to how they get their
carry out life functions or is released
energy.
back to the environment in the form
of heat, and is thus unusable.
Trophic Level
Large
 Because so little energy is available
4
carnivores
for transfer to the next trophic level,
energy pyramids rarely have more
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Small carnivores
than four levels.
 Organisms at lower trophic levels are
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Herbivores
more abundant than those at higher
levels. Higher trophic levels have
Producers
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less available energy and so can
support fewer organisms.