Splash

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Splash
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Chapter Introduction 1
Transport Systems

• How does this scene demonstrate the relationship
  between life, energy, and the biosphere?

• What is the source of energy that maintains these
  organisms?

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Chapter Introduction 2
Transport Systems

• Biologists agree that the ability to absorb and
  convert energy is a basic characteristic of
  life.

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End of the Introduction
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2.1 Characteristics of Organisms 1
Organisms and Energy
2.1 Characteristics of Organisms

• Living organisms have the following
  characteristics

• Take in and convert materials and energy from the
  environment release wastes
• Have a high degree of chemical organization
  compared to nonliving objects
• Have complex structural organization that is
  responsible for their appearance and activities
• Contain coded instructions (such as DNA) for
  maintaining their organization and activities

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2.1 Characteristics of Organisms 2
Organisms and Energy
2.1 Characteristics of Organisms (cont.)

• Living organisms have the following
  characteristics

• Sense and react to changes in their environment

• Grow and develop during some part of their lives
• Reproduce others like themselves
• Communicate with similar organisms
• Move under their own power

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2.2 Energy and Nutrients 1
Organisms and Energy
2.2 Energy and Nutrients

• Energy, the capacity to do work or to cause
  change, is needed by all living things.

• Organisms store chemical energy in the organic
  molecules from which the organisms are made.

• The portion of this chemical energy that is
  available to do work is called free energy.

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2.2 Energy and Nutrients 2
Organisms and Energy
2.2 Energy and Nutrients (cont.)

• Living cells need a constant source of free
  energy for chemical and mechanical work and for
  transport.

• Heterotrophs are organisms that obtain energy
  and nutrients from other organisms, either
  living or dead.

• Autotrophs are organisms that obtain energy and
  nutrients from nonliving sources such as the Sun,
  minerals, and the air.

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2.2 Energy and Nutrients 3
Organisms and Energy
2.2 Energy and Nutrients (cont.)

• Photoautotrophs are autotrophs that capture
  energy from sunlight and use it to synthesize
  organic compounds from carbon dioxide and water
  in a process called photosynthesis.

• Chemoautotrophs are autotrophs, all of which are
  bacteria, that use chemosynthesis to capture
  energy, which is stored as chemical energy and
  used for cellular work.

• Autotrophs use the organic compounds they make as
  building blocks for maintenance, growth, and
  reproduction.

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2.2 Energy and Nutrients 4
Organisms and Energy
2.2 Energy and Nutrients (cont.)

• Heterotrophs consume autotrophs and other
  heterotrophs as food.

• Autotrophs directly or indirectly supply the
  energy and organic nutrients needed for the
  maintenance, growth, and reproduction of all
  heterotrophs.
• Both autotrophs and heterotrophs carry out
  chemical reactions, known as cell respiration,
  that release the free energy of organic
  compounds.

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2.2 Energy and Nutrients 5
Organisms and Energy
2.2 Energy and Nutrients (cont.)
In the relationship between autotrophs and
heterotrophs, energy passes from autotrophs to
heterotrophs. Oxygen and carbon dioxide cycle
repeatedly between them.
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2.3 Energy and Ecosystems 1
Organisms and Energy
2.3 Energy and Ecosystems

• The need for energy and nutrients links organisms
  in many complex ways.

• Autotrophs, which produce food other organisms
  use, are the producers in a community of living
  organisms, such as a forest or an ocean.

• Heterotrophs consume plants and other organisms
  for food they are the consumers.

• Bacteria, fungi, and other heterotrophs that
  break down and use dead plants and animals for
  food are decomposers.

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2.3 Energy and Ecosystems 2
Organisms and Energy
2.3 Energy and Ecosystems (cont.)

• Producers, consumers, and decomposers form a food
  web in which energy and nutrients flow from the
  environment through the producers to the
  consumers and finally to the decomposers.

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End of Section 1
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2.4 Energy Conversions 1
Energy Flow
2.4 Energy Conversions

• Energy conversions are described by principles
  called the laws of thermodynamics.

• The first law of thermodynamics states that
  energy cannot be created or destroyed, but it can
  change form.

• On a broader scale, the first law is called the
  law of conservation of energy and it states that
  the total energy of the universe is constant.

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2.4 Energy Conversions 2
Energy Flow
2.4 Energy Conversions (cont.)

• The first law of thermodynamics means that
  organisms cannot create their own energy, but
  must obtain it from an outside source.

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2.5 Energy and Entropy 1
Energy Flow
2.5 Energy and Entropy

• The second law of thermodynamics states that
  systems tend to change in a way that increases
  the disorder, or entropy, of the system plus its
  surroundings.

• Because energy tends to spread out into the
  surroundings, the free energy in a system is
  slightly less after each energy conversion than
  before.
• The world becomes increasingly disordered as free
  energy is released.

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2.5 Energy and Entropy 2
Energy Flow
2.5 Energy and Entropy (cont.)

• Organisms must be well organized to remain alive
  and to grow.

• Energy is the key to maintaining organization in
  all living systems.
• In ecosystems, light or chemical energy flows
  from the environment (the Sun or inorganic
  chemicals) to producers to consumers to
  decomposers.

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2.5 Energy and Entropy 3
Energy Flow
2.5 Energy and Entropy (cont.)

• As energy flows through food webs, it eventually
  escapes in the form of heat energy, resulting in
  a one-way flow of energy.

• Living systems overcome the tendency toward
  entropy by constantly obtaining energy from their
  surroundings.
• Organisms stay organized and can function and
  grow only as the entropy of their surroundings
  increases.

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2.5 Energy and Entropy 4
Energy flow in an ecosystem
Click the image to view an animated version.
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End of Section 2
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2.6 Enzymes and Energy 1
Metabolism and Energy Transfer
2.6 Enzymes and Energy

• To release chemical energy to perform work,
  cells must have a way to break and form
  chemical bonds.

• All living cells contain specialized proteins
  called enzymes that lower the activation energy
  required to make a reaction proceed.

• Chemicals, such as enzymes, that lower activation
  energies are called catalysts.

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2.6 Enzymes and Energy 2
Metabolism and Energy Transfer
2.6 Enzymes and Energy (cont.)
Consider the starting molecule, S, and the
product molecule, P, which can be formed from S
through a chemical reaction. To achieve an
activated condition S, S must acquire
considerable energy.
In an enzyme-catalyzed reaction, S combines
temporarily with the enzyme E, forming a complex
ES, in which S requires less energy to form P
(the barrier is lower).
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2.6 Enzymes and Energy 3
Metabolism and Energy Transfer
2.6 Enzymes and Energy (cont.)

• Each type of enzyme catalyzes only one or a few
  specific reactions.

• The specific reaction catalyzed by an enzyme
  depends on a small area of its tertiary structure
  called the active site.

• The close fit of the starting molecule, called
  the substrate, into the active site of the enzyme
  brings the enzyme and substrate close together.

• The resulting interaction lowers the activation
  energy, which allows the chemical reaction from
  substrate to product to proceed.

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2.6 Enzymes and Energy 4
The induced-fit model of enzyme action
Click the image to view an animated version.
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2.7 Chemical Reactions in Organisms 1
Metabolism and Energy Transfer
2.7 Chemical Reactions in Organisms

• Metabolism consists of all the chemical
  activities and changes that take place
  continuously in a cell or an organism.

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2.8 Energy Transfer and ATP 2
Metabolism and Energy Transfer
2.8 Energy Transfer and ATP (cont.)

• ATP is a nucleotide consisting of adenine and
  ribose joined to a chain of three phosphate
  groups.

• Usually when an ATP molecule is involved in a
  chemical reaction, the bond between the second
  and third phosphate groups breaks and free energy
  is released.

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2.8 Energy Transfer and ATP 3
Metabolism and Energy Transfer
2.8 Energy Transfer and ATP (cont.)

• A molecule that accepts the phosphate group from
  ATP gains free energy and is activated it can
  then react usefully with other molecules in the
  cell.

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2.8 Energy Transfer and ATP 5
Metabolism and Energy Transfer
2.8 Energy Transfer and ATP (cont.)

• ATP is continually synthesized and broken down in
  cells, forming a cycle.

• ATP becomes ADP, adenosine diphosphate, when it
  gives up one phosphate group.

• ADP must combine with one phosphate group,
  requiring free energy from the breakdown of
  organic compounds to form ATP.

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End of Section 3
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2.9 Digestion Inside and Outside Cells 2
Digestion
2.9 Digestion Inside and Outside Cells (cont.)

• Digestion consists of two parts

• physicalthe breakdown of large pieces of food
  into smaller ones to increase surface area

• chemicalthe breaking down of complex food
  molecules into simpler ones

In some birds, food is temporarily stored in a
sac called a crop. Farther along the digestive
tract, a specialized part of the stomachthe
gizzardgrinds up food to aid digestion. The
walls of the gizzard are thick and muscular, an
evolutionary adaptation to grinding. Some birds
swallow sand and small pebbles that aid the
grinding action.
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2.9 Digestion Inside and Outside Cells 3
Digestion
2.9 Digestion Inside and Outside Cells (cont.)

• Most animals, including humans, rely on
  extracellular digestiondigestion that takes
  place outside the cells.

• Most animals secrete digestive enzymes into a
  digestive cavity, where chemical digestion yields
  the simpler molecules that are then absorbed by
  the cells.

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2.9 Digestion Inside and Outside Cells 4
Digestion
2.9 Digestion Inside and Outside Cells (cont.)

• Most plants rely on intracellular
  digestiondigestion that takes place inside the
  cells with foods the plant has made itself.

• Single-celled organisms, such as Paramecium, also
  rely on intracellular digestion.

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2.9 Digestion Inside and Outside Cells 5
Digestion
2.9 Digestion Inside and Outside Cells (cont.)

• Many organisms, such as Venus flytraps and bread
  mold produce enzymes that digest food outside the
  organism itself and then absorb the nutrients
  into the cells.

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End of Chapter Presentation