Photosynthesis

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Photosynthesis

• Energy Life

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Autotrophs

• Plants and some other types of organisms that
  contain chlorophyll are able to use light energy
  from the sun to produce food.

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Autotrophs

• Autotrophs include organisms that make their own
  food
• Autotrophs can use the suns energy directly

Euglena
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Heterotrophs

• Heterotrophs are organisms that can NOT make
  their own food
• Heterotrophs can NOT directly use the suns
  energy

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Energy

• Energy Takes Many Forms such as light, heat,
  electrical, chemical, mechanical
• Energy can be changed from one form to another
• Energy can be stored in chemical bonds then
  released later

Candles release energy as HEAT LIGHT
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ATP Cellular Energy

• Adenosine Triphosphate
• Contains two, high-energy phosphate bonds
• Also contains the nitrogen base adenine a
  ribose sugar

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ADP

• Adenosine Diphosphate
• ATP releases energy, a free phosphate, ADP when
  cells take energy from ATP

One phosphate bond has been removed
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Sugar in ADP ATP

• Called ribose
• Pentose sugar
• Also found on RNA

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Importance of ATP

• Principal Compound Used To Store Energy In Living
  Organisms

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Releasing Energy From ATP

• ATP is constantly being used and remade by cells
• ATP provides all of the energy for cell
  activities
• The high energy phosphate bonds can be BROKEN to
  release energy
• The process of releasing ATPs energy reforming
  the molecule is called phosphorylation

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Releasing Energy From ATP

• Adding A Phosphate Group To ADP stores Energy in
  ATP
• Removing A Phosphate Group From ATP Releases
  Energy forms ADP

Loose
Gain
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Cells Using Biochemical Energy

• Cells Use ATP For
• Active transport
• Movement
• Photosynthesis
• Protein Synthesis
• Cellular respiration
• All other cellular reactions

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More on ATP

• Cells Have Enough ATP To Last For A Few Seconds
• ATP must constantly be made
• ATP Transfers Energy Very Well
• ATP Is NOT Good At Energy Storage

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Glucose

• Glucose is a monosaccharide
• C6H12O6
• One Molecule of glucose Stores 90 Times More
  Chemical Energy Than One Molecule of ATP

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Photosynthesis

• Involves the Use Of light Energy to convert Water
  (H20) and Carbon Dioxide (CO2) into Oxygen (O2)
  and High Energy Carbohydrates (sugars, e.g.
  Glucose) Starches

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Investigating Photosynthesis

• Many Scientists Have Contributed To Understanding
  Photosynthesis
• Early Research Focused On The Overall Process
• Later Researchers Investigated The Detailed
  Chemical Pathways

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The Photosynthesis Equation
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Pigments

• In addition to water, carbon dioxide, and light
  energy, photosynthesis requires Pigments
• Chlorophyll is the primary light-absorbing
  pigment in autotrophs
• Chlorophyll is found inside chloroplasts

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Light and Pigments

• Energy From The Sun Enters Earths Biosphere As
  Photons
• Photon Light Energy Unit
• Light Contains A Mixture Of Wavelengths
• Different Wavelengths Have Different Colors

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Light Pigments

• Different pigments absorb different wavelengths
  of light
• Photons of light excite electrons in the
  plants pigments
• Excited electrons carry the absorbed energy
• Excited electrons move to HIGHER energy levels

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Chlorophyll

• There are 2 main types of chlorophyll molecules
• Chlorophyll a
• Chlorophyll b
• A third type, chlorophyll c, is found in
  dinoflagellates

Magnesium atom at the center of chlorophyll
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Chlorophyll a

• Found in all plants, algae, cyanobacteria
• Makes photosynthesis possible
• Participates directly in the Light Reactions
• Can accept energy from chlorophyll b

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Chlorophyll b

• Chlorophyll b is an accessory pigment
• Chlorophyll b acts indirectly in photosynthesis
  by transferring the light it absorbs to
  chlorophyll a
• Like chlorophyll a, it absorbs red blue light
  and REFLECTS GREEN

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The Biochemical Reactions
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Inside A Chloroplast
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Structure of the Chloroplast

• Double membrane organelle
• Outer membrane smooth
• Inner membrane forms stacks of connected sacs
  called thylakoids
• Thylakoid stack is called the granun
  (grana-plural)
• Gel-like material around grana called stroma

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Function of the Stroma

• Light Independent reactions occur here
• ATP used to make carbohydrates like glucose
• Location of the Calvin Cycle

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Thylakoid membranes

• Light Dependent reactions occur here
• Photosystems are made up of clusters of
  chlorophyll molecules
• Photosystems are embedded in the thylakoid
  membranes
• The two photosystems are
• Photosytem I
• Photosystem II

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Photosynthesis Overview
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Energy Carriers

• Nicotinamide Adenine Dinucleotide Phosphate
  (NADP)
• NADP Reduced Form
• Picks Up 2 high-energy electrons and H from the
  Light Reaction to form NADPH
• NADPH carries energy to be passed on to another
  molecule

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Light Dependent Reactions

• Occurs across the thylakoid membranes
• Uses light energy
• Produce Oxygen from water
• Convert ADP to ATP
• Also convert NADP into the energy carrier NADPH

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Light Dependent Reaction
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Photosystem I

• Discovered First
• Active in the final stage of the Light Dependent
  Reaction
• Made of 300 molecules of Chlorophyll
• Almost completely chlorophyll a

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Photosystem II

• Discovered Second
• Active in the beginning stage Of the Light
  Dependent Reaction
• Contains about equal amounts of chlorophyll a and
  chlorophyll b

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Photosynthesis Begins

• Photosystem II absorbs light energy
• Electrons are energized and passed to the
  Electron Transport Chain
• Lost electrons are replaced from the splitting of
  water into 2H, free electrons, and Oxygen
• 2H pumped across thylakoid membrane

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Photosystem I

• High-energy electrons are moved to Photosystem I
  through the Electron Transport Chain
• Energy is used to transport H from stroma to
  inner thylakoid membrane
• NADP converted to NADPH when it picks up 2
  electrons H

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Phosphorylation

• Enzyme in thylakoid membrane called ATP
  Synthetase
• As H ions passed through thylakoid membrane,
  enzyme binds them to ADP
• Forms ATP for cell

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Light Reaction Summary

• Reactants
• H2O
• Light Energy
• Energy Products
• ATP
• NADPH

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Light Independent Reaction

• ATP NADPH from light reactions used as energy
• Atmospheric C02 is used to make sugars like
  glucose and fructose
• Six-carbon Sugars made during the Calvin Cycle
• Occurs in the stroma

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The Calvin Cycle
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The Calvin Cycle

• Two turns of the Calvin Cycle are required to
  make one molecule of glucose
• 3-CO2 molecules enter the cycle to form several
  intermediate compounds (PGA)
• A 3-carbon molecule called Ribulose Biphosphate
  (RuBP) is used to regenerate the Calvin cycle

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Factors Affecting the Rate of Photosynthesis

• Amount of available water
• Temperature
• Amount of available light energy