Photosynthesis

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Photosynthesis

• Watch this http//youtu.be/g78utcLQrJ4

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CO 7
Chapter 7 Photosynthesis
Name a plant you have seen recently.
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Brainstorm...

• What are some careers or college majors related
  to plants?

U of I - College of Agriculture
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What is a plant anyway?7.1 Photosynthetic
Organisms A. Photosynthesis transforms solar
energy B. Organic molecules built by
photosynthesis provide both the building blocks
and energy for cells.
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Figure 7.1b
C. Plants use the raw materials carbon dioxide
and water D. Chloroplasts carry out
photosynthesis
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Figure 7.1c
E. Chlorophylls and other pigments involved in
absorption of solar energy reside within
thylakoid membranes of chloroplasts
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Figure 7.2
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Quick Check - FIVE OR FEWER 1.  Plant 2.
 Thylakoid 3.  Photosynthesis 4.  Organic
Molecules
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7.2 Plants as Solar Energy ConvertersA. Solar
Radiation - Only 42 of solar radiation that hits
the earths atmosphere reaches surface most is
visible light.
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• B. Photosynthetic Pigments - Pigments found in
  chlorophyll absorb various portions of visible
  light absorption spectrum.
• 1. Two major photosynthetic pigments are
  chlorophyll a and chlorophyll b.2. Both
  chlorophylls absorb violet, blue, and red
  wavelengths best.3.  Most green is reflected
  back this is why leaves appear green.

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4. Carotenoids are yellow-orange pigments which
absorb light in violet, blue, and green
regions.5. When chlorophyll breaks down in fall,
the yellow-orange pigments in leaves show through.
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Fall Foliage Slideshow
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Fall Leaves

• Why do leaves turn orange/red/brown in the fall?
• What are the major pigments which absorb light?
• Why do leaves appear green?

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D. Photosynthetic Reaction 1. In 1930 C. B. van
Niel showed that O2 given off by photosynthesis
comes from water and not from CO2.2. The net
equation reads
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E. Two Sets of Reactions in Photosynthesis1.
Light reactions cannot take place unless light is
present. They are the energy-capturing reactions.
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• b. Chlorophyl within thylakoid membranes absorbs
  solar energy and energizes electrons.
• c. Energized electrons move down the electron
  transport system energy is captures and used for
  ATP production.
• d. Energized electrons are also taken up by
  NADP, becoming NADPH.

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2. Calvin Cycle Reactions a. These reactions take
place in the stroma can occur in either the
light or the dark. b. These are synthesis
reactions that use NADPH and ATP to reduce CO2.
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What you should know by now..

• 1.  The equation for photosynthesis.  Write it!
• 2.  The structure of a chloroplast.  Sketch it!
• 3.  Compare the two stages of photosynthesis and
  their products.  Chart it!
• Things are about to get much more difficult

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7.3 The Light Reactions

• 1.  Two paths operate within the thylakoid
  membrane
•                          noncyclic            
   and                cyclic
•                           straight line        
                in a circle
• 2.  Both paths use ATP, but the noncyclic also
  produces NADPH
• (this is where we pick up electrons!)
• 3.  PHOTOPHOSPHORYLATION ATP production
• (phosphorylation means adding a P to ADP ? ATP)

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1. Light hits photosystem II (yes, II comes
before I)and exites an electron in H20 2.  The
primary electron acceptor passes the electron
down the ETC and generates ATP 3. Light is
required for PSI, but not water, it generates
NADPH
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Something trivial....Photosystem I and
Photosystem II are named based on when they were
discovered, PSI was established first.
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Figure 7.5
We use these electrons to go to the Calvin Cycle
Weve used our electrons here to form ATP
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Indicate which system  (PS1 or PS2 or BOTH)

• ____1.  Splits water
• ____2.  Produces NADPH____3.  Has an electron
  transport chain
• ____4.  Requires light
• ____5.  Utilizes a primary electron acceptor
• ____6.  Occurs in the thylakoid
• ____7.  Requires the input of H20
• ____8.  The cyclic path____9.  Uses chlorophyll
• ____10.  Releases oxygen

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Are you still confused?    This is pretty hard to
visualize, but through the magic of technology,
we can watch these processes as animations

• McGraw Hill Animation
• Forest Biology - The Light Reactions

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7.3   Light Reactions        A.  Two Pathways   
B.  Noncyclic    C.  Cyclic    D.   ATP
Production  --gt  CHEMIOSMOSIS            When
H20 is split, two H remain            These H
are pumped from the stroma into the thylakoid   
         This creates a gradient used to produce
ATP from ADP ATP is the whole point of
Photosystem II and will be used to power the
Light Independent Reactions (Calvin Cycle)
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Figure 7.7
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(No Transcript)
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Chemiosmosis is difficult to visualize.So...
you get to color it!
Yay!  coloring!
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The Calvin Cycle  

• Also called
• The Light Independent Reactions
• The Dark Reactions
• Named after Melvin Calvin, who used a
  radioactive isotope of carbon to trace the
  reactions.

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The Calvin Cycle

• is a series of reactions producing
  carbohydrates.carbon dioxide fixation, carbon
  dioxide reduction, and regeneration of RuBP.

FIXATIONREDUCTIONREGENERATION
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B. Fixation of Carbon Dioxide

• 1. CO2 fixation is the attachment of CO2 to an
  organic compound called RuBP.
• 2. RuBP (ribulose bisphosphate) is a five-carbon
  molecule that combines with carbon dioxide.

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• 3. The enzyme RuBP carboxylase (rubisco) speeds
  this reaction this enzyme comprises 2050 of
  the protein content of chloroplasts, probably
  since it is a slow enzyme.

Calvin Cycle Animation
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C. Reduction of Carbon Dioxide
1. With reduction of carbon dioxide, a
PGA  (3-phosphoglycerate C3) molecule forms.
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D. Regeneration of RuBP

• 1. Every three turns of Calvin cycle, five
  molecules of PGAL are used to re-form three
  molecules of RuBP.
• 2. Every three turns of Calvin cycle, there is
  net gain of one PGAL molecule five PGAL
  regenerate three molecules of RuBP.

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Figure 7.8
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E. The Importance of the Calvin Cycle

• 1. PGAL, the product of the Calvin Cycle can be
  converted into all sorts of other molecules.
• 2. Glucose phosphate is one result of PGAL
  metabolism it is a common energy molecule.

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Figure 7.9
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Factors the Affect Photosynthesis   1. Light
Quality (color)2. Light intensity3. Light
Period4. Carbon Dioxide Availability5. Water
Availability
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• In order for photosynthesis to occur, plants must
  open tiny pores on their leaves called STOMATA.
• Opening these pores can lead to loss of water.

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• Alternative Pathways
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• The Calvin Cycle is the MOST Common Pathway for
  Carbon Fixation. Plant Species that fix Carbon
  EXCLUSIVELY through the Calvin Cycle are known as
  C3 PLANTS. 
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• Plants in hot dry environments have a problem
  with water loss, so they keep their stomata
  partly closed... this results in
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• CO2  deficit (Used in Calvin Cycle), and the
  level of O2 RISES                 (as Light
  reactions Split Water Molecules).

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Figure 7.10
C4 plants and CAM (Crassulacean acid metabolism)
plants use an alternate pathway to FIX carbon
dioxide from the air.
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Figure 7.11
THE CAM PATHWAY - Plants that use the CAM Pathway
open their stomata at night and close during the
day.   At night, CAM Plants take in CO2 and fix
into organic compounds. During the day, CO2 is
released from these Compounds and enters the
Calvin Cycle. Because they have their stomata
open only at night, they grow slow.
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Quick Practice
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Quick Practice
grana
thylakoid
stroma
O2
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Pg 129b
Light H2O
CO2
ADP
NADP
ATP
NADPH
O2
glucose
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A photosystem IIB photosystem I C H20 D
Electron Transport Chain E ATP Synthase
AB ATP AC phospholipids AD light (energy)