Energy, Life and the Biosphere

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Energy, Life and the Biosphere
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Energy

• Energy exists in many forms, such as heat, light,
  chemical energy, and electrical energy. Energy is
  the ability to bring about change or to do work.

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Energy Conversion

• Energy must be converted from one form to another
  to do work.

 A flashlight converts the chemical energy stored
in batteries into light and heat. Most of the
energy is converted to heat. Only a small
percentage of the original energy in the battery
is converted into light energy.
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Energy and Nutrients

• Organisms store energy in the organic molecules
  from which organisms are made (chemical energy).
• The portion available to do work is called free
  energy.
• How do organisms obtain energy?

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Obtaining Energy

• Autotrophs obtain nutrients and from nonliving
  sources such as the Sun, minerals, and the air.
• Autotrophs use photosynthesis (photoautotroph) or
  chemosynthesis (chemoautotroph) to synthesize
  organic compounds that are stored as chemical
  energy.
• Autotrophs are the producers.

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Obtaining Energy

• Heterotrophs obtain energy and nutrients from
  other organisms.
• Heterotrophs are consumers.
• They may be carnivores, omnivores, herbivores, or
  detritivores.

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Releasing Energy

• Both Autotrophs and Heterotrophs carry out
  chemical reactions that release the free energy
  of organic compounds. This process is known as
  cell respiration.

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Food Webs

• A food web is a description of how energy flows.
• It flows from the environment through producers
  to consumers and then decomposers.

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Food Chains
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Ecosystems

• Abiotic factors are the nonliving components of
  an ecosystem - soil, water, minerals, weather
• Biotic factors are the living components of an
  ecosystem the organisms that live there.
• Both components make up and ecosystem forest,
  prairie, pond.

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Ecosystems
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Ecosystems and the Biosphere

• Within an ecosystem are many habitats- places
  where organisms live- at the top of a tree, in
  the soil, at the bottom of a pond, at the edge of
  the ocean.
• All of the ecosystems in the world make up the
  biosphere.

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Energy Conversions

• First Law of Thermodynamics Energy can be
  changed from one form to another, but it cannot
  be created or destroyed. The total amount of
  energy and matter in the Universe remains
  constant, merely changing from one form to
  another.

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Energy and Entropy

• The Second Law of Thermodynamics states that
  systems tend to change in a way that increases
  the disorder (entropy).
• The world becomes increasingly disordered as free
  energy is released.
• Organisms must remain organized to stay alive-
  the key is an input of energy.

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Energy Flow

• As energy flows through a food web, some of the
  energy is converted to heat, which escapes into
  the surroundings.

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How is Energy Transferred?

• Cells must break and form chemical bonds to
  release chemical energy to do work.
• Chemical reactions take place in a narrow range
  of temperatures.
• Those temperatures are not high enough to supply
  the activation energy (energy needed to start a
  reaction)

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Catalysts

• Catalysts are chemicals that lower the energy
  needed to make a reaction happen.
• Enzymes, special proteins, are catalysts in
  living organisms.

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Enzymes

• Each enzyme catalyzes one or a very few specific
  reactions.
• The structure of an enzyme is what makes it so
  specific.
• Enzymes have active sites that match their
  substrates (starting molecule).

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Enzymes and Substrates
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Induced Fit Model of Enzyme Action

• The change in shape of the active site of an
  enzyme so that it binds more snugly to the
  substrate, induced by entry of the substrate.

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Chemical Reactions

• Metabolism is all of the chemical reactions in a
  cell or organism.
• There are two types
• Synthesis or building up reactions
• Decomposition or breaking down reactions

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Synthesis Reactions
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Decomposition Reactions
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Examples of Biosynthesis Reactions

• Building proteins from amino acids, which then
  build tissues from proteins.
• Photosynthesis builds sugars from CO2 and H20

Biosynthesis reactions consume free energy
because the products are more ordered and contain
more energy than the reactants.
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Decomposition Reactions

• The breakdown of starch into glucose
• The breakdown of proteins into amino acids.

Decomposition reactions release free energy
because the produce simple molecules from complex
molecules.
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The Release of Energy

• Decomposition releases free energy through a
  process called oxidation.
• Oxidation is the removal of electron(s) from a
  molecule.
• The energy released when the bonds are broken and
  rearranged goes through a set of electron
  transfers to become ATP

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ATP

• Adenosine Triphosphate is the energy currency
  of the cell.

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ATP
ATP is the chemical energy that drives the
reactions of the cell.

• Much like a tourist in a foreign country must pay
  a fee to change their money into the currency of
  the land - A cell carries out chemical reactions
  that exchange chemical energy of organic
  compounds (food) for the chemical energy of ATP.
  ATP pays the energy debts inside a cell. The
  fee is the energy that is lost as heat.

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How ATP Cycles

• ATP is an efficient energy transfer molecule
  because when it is involved in a chemical
  reaction, the bond between the 2nd and 3rd
  phosphate groups breaks and releases free energy.
• The released phosphate group takes the free
  energy with it to a molecule that accepts it,
  thus the molecule gains free energy.

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ATP- ADP Cycle

• When the terminal P group is released, the
  molecule becomes ADP adenosine diphosphate.
• ADP is then cycled back to ATP when it gains a P
  group (which happens during cellular
  respiration).
• ATP is re-used by being cycled from ATP to ADP to
  ATP again.

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The ATP ADP Cycle