Photosynthesis and Cellular Respiration

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Photosynthesis and Cellular Respiration

• Energy for Life

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Complementary processes

• Photosynthesis is an important part of the carbon
  cycle.
• The processes of photosynthesis and cellular
  respiration are complementary processes, meaning
  they work together to benefit living organisms.

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Plants and animals contribute

• Autotrophs, such as plants, produce glucose using
  the carbon in carbon dioxide.
• Both autotrophs and heterotrophs, such as
  grasshoppers that eat plants, use those
  carbohydrates in cellular respiration.
• Respiration, in turn, produces carbon dioxide.

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Photosynthesis equation

• light
• 6 CO2 6 H2O C6H12O6 6O2
• Photosynthesis combines water, carbon dioxide and
  sunlight to produce glucose and oxygen,
  converting light energy into chemical energy.

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Respiration equation

• 6O2 C6H12O6 6CO2 H2O Energy
• Respiration breaks down glucose and other food
  molecules in the presence of oxygen.

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Energy renewal

• Energy captured from sunlight by photosynthetic
  organisms is used and released in the cellular
  respiration of living things.
• The energy that living things use, must
  continually be renewed through photosynthesis.

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Where does photosynthesis occur?

• In plants and other photosynthetic eukaryotes,
  photosynthesis takes place inside chloroplasts.
• The chloroplasts contain saclike membranes called
  thylakoids.
• Thylakoids are arranged in stacks known as grana.

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Photosystems

• Proteins in the thylakoid organize chlorophyll
  and other pigments into light-collecting units
  called photosystems.

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What are the reactions of photosynthesis?

• Scientists divide the reactions of photosystems
  into two parts Light-dependent reactions and
  light-independent reactions or the Calvin cycle.
• The light-dependent reactions take place within
  the thylakoid membranes.
• They use energy from light to produce ATP and
  NADPH, which are energy carriers.

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Light-dependent reactions

• Photosystem II absorbs light and breaks water
  molecules into energized electrons, hydrogen ions
  (H) and oxygen.
• High-energy electrons move through the electron
  transport chain from photosystem II to
  photosystem I.
• As electrons pass from chlorophyll to NADP, more
  hydrogen ions are pumped across the membrane.
• ATP synthase in the membrane allows H ions to
  pass through it. The enzyme binds ADP and a
  phosphate group to produce ATP.

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Light-dependent reactions
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Light-dependent reactions
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Light-independent reactions

• The light-independent reactions of the Calvin
  Cycle take place in the stroma outside of the
  thylakoid membranes.
• The Calvin Cycle uses ATP and NADPH from the
  light-dependent reactions to produce high-energy
  sugars.

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Light-independent reactions
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What is the visible spectrum of light and why is
it important?

• The visible spectrum of light is the set of
  varying wavelengths of light that are visible to
  our eyes as different colors.
• Sunlight is a mixture of different wavelengths of
  light, even though it appears as white light to
  your eyes.

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The visible spectrum
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Pigments absorb light

• In addition to water and carbon dioxide,
  photosynthesis requires light and chlorophyll, a
  pigment molecule within chloroplasts.
• The two main types are chlorophyll a and
  chlorophyll b.
• Chlorophyll absorbs blue-violet and red light
  very well. Green light is reflected by plant
  leaves, which is what gives them their green
  color.

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Light absorption powers photosynthesis

• Chlorophyll absorbs blue-violet and red light
  very well. Green light is reflected by plant
  leaves, which is what gives them their green
  color.
• The high-energy electrons produced when
  chlorophyll absorbs light make photosynthesis
  work.

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Photosynthesis Review
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Photosynthesis Review
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Photosynthesis Review
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Cellular Respiration
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Living things need energy

• Our bodies have a lot of work to do every day
• Moving muscles,
• Building essential molecules, and
• Transporting substances across cell membranes.

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Where do we get energy?

• Food provides the energy living things need to
  grow and reproduce.
• Food is the source of the material our cells use
  to build new molecules.

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How much energy is present in food?

• Quite a lot!
• One gram of the sugar glucose (C6H12O6) when
  burned in the presence of oxygen, releases 3,811
  calories of heat energy.
• A calorie is the amount of energy needed to raise
  the temperature of 1 gram of water 1 degree
  Celsius.

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What is cellular respiration?

• Cellular respiration is the process that releases
  energy by breaking down glucose and other food
  molecules in the presence of oxygen.

6O2 C6H12O6
6CO2 6H2O Energy
carbon dioxide water energy
oxygen glucose
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Where does cellular respiration take place?

• The beginning pathway of cellular respiration,
  glycolysis, takes place in the cell cytoplasm.
• The two remaining pathwaysthe Krebs Cycle and
  electron transporttake place inside the
  mitochondria of the cell.

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Cellular Respiration Overview

• Glycolysis a glucose molecule is split to
  produce two molecules of pyruvic acid.
• Krebs Cycle pyruvic acid is used to produce
  carbon dioxide, NADH, ATP and FADH2. Sometimes
  called the citric acid cycle because citric acid
  is first formed.
• Electron Transport Chain uses high-energy
  electrons from the Krebs Cycle to convert ADP to
  ATP.

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Glycolysis
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Kreb Cycle
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Kreb Cycle
ATP
NETS 3NADH, 1ATP, 1FADH2, 2CO2
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What happens if oxygen is not available?

• Glycolysis is then followed by a different
  pathway.
• The combined process of this pathway and
  glycolysis is called fermentation.
• Fermentation releases energy from food molecules
  by producing ATP in the absence of oxygen.

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Fermentation
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Cellular Respiration Summary