A simple review.. Do you remember

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A simple review.. Do you remember?????

• Cellular respiration As you begin
  photosynthesis look for similarities and
  differences in these two energy producing
  reactions
• les mitochondries

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Photosynthesisan overview
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Present knowledge regarding light

• First stage requires light, reduces electron
  carriers, makes ATP from ADP
• In second stage carriers and ATP reduces C in CO2
  and makes glucose Carbon fixation incorporates
  CO2 carbon into glucose in "dark" reaction

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Structure of the Leaf
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Upper epidermis.

• Transparent cells
• Covered in a waxy cuticle which decreases water
  loss

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Palisade layer

• cylindrical cells
• filled with chloroplasts (usually several dozen
  of them)
• Site of photosynthesis
• (arrows point to stomata)

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Stomata

• microscopic pores found on the under side of
  leaves.
• bounded by two half moon shaped guard cells that
  function to vary the width of the pore.

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Spongy Mesophyll layer

• irregular in shape and loosely packed.
• their main function seems to be the temporary
  storage of sugars and amino acids synthesized in
  the palisade layer.

• Google Image Result for http//www.mansfield.osu.e
  du/jbradley/LeafXSNumbered.jpg

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Chloroplast

• Each mesophyll cell has 30 to 40 chloroplasts.

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Overview chloroplast

• http//www.rkm.com.au/imagelibrary/thumbnails/chlo
  roplast-150.jpg

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Chloroplast

• responsible for photosynthesis.
• contains a permeable outer membrane, a less
  permeable inner membrane, a intermembrane space,
  and an inner section called the stroma.
• larger than the mitochondria
• not folded into cristae.
• forms a series of flattened discs, called the
  thylakoids.

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• http//www.mhhe.com/biosci/genbio/tlw2/student/olc
  /graphics/johnson2tlw_s/ch08/others/mi08-04b.dcr

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• The innermost membrane of the chloroplast is
  called the thylakoid membrane.
• The thylakoid membrane is folded upon itself
  forming many disks called grana (singular
  granum).
• The "cytoplasm" of the chloroplast is called the
  stroma

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• Chapter 32 Introduction practice naming
  anatomy and physiology of leaf

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Nature of Sunlight

• The energy of is inversely proportional to the
  wavelength longer wavelengths have less energy
  than do shorter ones.

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• The order of colors is determined by the
  wavelength of light.

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• Light behaves both as a wave and a particle. Wave
  properties of light include the bending of the
  wave path when passing from one material (medium)
  into another (i.e. the prism, rainbows, pencil in
  a glass-of-water, etc.). The particle properties
  are demonstrated by the photoelectric effect.
  Zinc exposed to ultraviolet light becomes
  positively charged because light energy forces
  electrons from the zinc. These electrons can
  create an electrical current.

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Photons

• Although light may be described as a traveling
  wave propagating through space
• we can also discuss its behavior in terms of the
  amount of energy imparted in an interaction with
  some other medium
• In this case, we can imagine a beam of light to
  be composed of
• a stream of small lumps or QUANTA of energy,
  known as PHOTONS
• each photon carries with it a precisely defined
  amount of energy
• this energy depends only on its wavelength or
  frequency
• The energy of a single photon is given, in terms
  of its frequency, f, or wavelength, Atomic
  absorption diagram

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• Pigments absorb light.

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Pigments

• A pigment is any substance that absorbs light.
  The color of the pigment comes from the
  wavelengths of light reflected (in other words,
  those not absorbed).

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Chlorophyll

• Chlorophyll is a complex molecule. Several
  modifications of chlorophyll occur among plants
  and other photosynthetic organisms.

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Chlorophyll a

• All photosynthetic organisms (plants, certain
  protistans, prochlorobacteria, and cyanobacteria)
  have chlorophyll a.

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Map of chlorophyll a
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• Chlorophyll a absorbs its energy from the
  Violet-Blue and Reddish orange-Red wavelengths,
  and little from the intermediate
  (Green-Yellow-Orange) wavelengths.
• Chlorophyll A is the main photosynthetic pigment
  in all organisms except bacteria.

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Accessory pigments

• Accessory pigments absorb energy that chlorophyll
  a does not absorb. Accessory pigments include
  chlorophyll b (also c, d, and e in algae and
  protistans), xanthophylls, and carotenoids (such
  as beta-carotene).

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Compare wavelength absorbed

• 1. Chlorophyll a Light to medium green. Main
  photosynthetic pigment.
• 2. Chlorophyll b Blue-green. Accessory Pigment.
• 3. Carotene Orange. Accessory Pigment.
• 4. Xanthophyll Yellow. Accessory Pigment.

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Action and Absorption Spectrum

• Go to this site to learn more about these.
• Action Absorption Spectra

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Action Spectra

• The use of action spectra has been central to the
  development of our current understanding of
  photosynthesis. An action spectrum is a graph of
  the magnitude of the biological effect observed
  as a function of wavelength. Examples of effects
  measured by action spectra are oxygen evolution

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Action Spectrum
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Absorption Spectrum

• An absorption spectrum the wavelengths at which
  it can absorb light and enter into an excited
  state. The diagram represents the absorption
  spectrum of pure chlorophylls

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• http//academic.kellogg.edu/herbrandsonc/bio111/an
  imations/0053.swf

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Photoexcitation

• When a pigment absorbs a photon, one of the
  molecules electrons is elevated to an orbital
  with more potential energy (this excited state
  unstable).
• Only photons absorbed are those whose energy is
  exactly equal to the energy difference between
  the ground state and the excited state. This
  energy difference varies between pigments.

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Stages of Photosynthesis

• The first process is the Light Dependent Process
  (Light Reactions), requires the direct energy of
  light to make energy carrier molecules that are
  used in the second process.

• Harvesting Light
• Animation Quizzes (go to light independent
  reaction)
• Photosynthesis
• NetLearning - Examples - Flash

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There are two paths which can be taken

• Cyclic electron flow The simpler, involving
  only photosystem 1 and generates only
  ATP Animations
• Non cyclic uses both systems, generates ATP and
  NADPH and oxygen is released.

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Players in Light Reaction

• Photosystems
• The closely packed pigment molecules and the
  reaction center form a unit referred to as an
  antenna complex.

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• Photons of light that are picked up by any of the
  pigment molecules in the antenna pass their
  energy pigment molecules until it is eventually
  passed to a special molecule of chlorophyll a
  called the reaction center.

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Two types of photosystems

• Photosystem I, called PS 700
• Photosystem II, called PS 680
• Both named due to the wavelength they absorb
• Named according to when discovered.

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• The reaction center molecule becomes ionized and
  it loses its electron to an electron acceptor.
  This electron will need to be replaced.
• Water is split

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Details of the Light-Dependent Reactions

• Photosystem II - The antenna is shown as a single
  green circle. Notice that there are two
  photosystems and therefore two antennas. The blue
  circles represent the electron transport system

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• During the light reactions, pigment molecules
  within the P680 antenna absorb a photon of light
  energy. The energy from that molecule is passed
  to neighboring molecules and eventually makes its
  way to the reaction center molecule as previously
  described. When the reaction center molecule
  becomes excited, it loses its electron to an
  electron acceptor. (Redox)

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Photophosphorylation

• The electron transport system is found embedded
  within the thylakoid membrane and functions in
  the production of ATP. The system contains
  membrane-bound electron carriers that pass
  electrons from one to another. As a result of
  gaining an electron (reduction), the first
  carrier of the electron transport system gains
  energy. It uses some of the energy to pump H
  into the thylakoid.

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• ATP is produced from ADP and Pi when hydrogen
  ions pass out of the thylakoid through ATP
  synthase. This method of synthesizing ATP by
  using a H gradient in the thylakoid is called
  photophosphorylation.
• Animations

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One more look

• http//www.fw.vt.edu/dendro/forestbiology/photosyn
  thesis.swf

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Light Independent Reaction

• The products of the light reactions (ATP and
  NADPH) are used to reduce CO2 to carbohydrate in
  the Calvin cycle.

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• The words "CO2 fixation" refer to the attachment
  of CO2 to an organic compound each CO2 binds to
  a 5-carbon ribulose biphosphate (RuBP) molecule.
• Carbon dioxide fixation is catalyzed by RuBP
  carboxylase (rubisco).

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Nest comes the Calvin Cycle

• Calvin cycle
• calvin

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• six carbon dioxide molecules are combined with
  six RuBP molecules to produce six molecules of a
  6-carbon compound.

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• Each of the resulting 6-carbon molecules formed
  by carbon dioxide fixation (above) splits into
  two 3-carbon molecules (phosphoglycerate PGA)
  for a total of 12 PGA molecules

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• The two molecules of PGA are reduced to form PGAL
  (phosphoglyceraldehyde). The PGAL molecules also
  have three carbon atoms each. This reaction
  requires energy from ATP and electrons from NADPH.

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• Two of the PGAL molecules are used to form one
  glucose molecule (C6).  Ten PGAL remain.

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• The remaining 10 PGAL (3 carbons each, total 30
  carbons) can therefore be reassembled into 6 RuBP
  (5 carbons each, total 30 carbons). This
  rearrangement uses 6 ATP.

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• Calvin cycle

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• For each six CO2 molecules that enter the cycle
  one glucose molecule is produced.
• About 30 of the energy available in ATP and
  NADPH is finally present in the glucose produced.

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PhotorespirationAn evolutionary relic?

• Rubisco can accept oxygen in place of carbon
  dioxide (fixation) when levels of oxygen increase
  in the leaf air spaces
• Now lets watch the video which describes what
  happens. (Canadian as it is)

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C 3 and C 4 plants

• Almost all plant life on Earth can be broken into
  two categories based on the way they assimilate
  carbon dioxide into their systems.C3 plants
  include more than 95 percent of the plant species
  on earth. (Trees, for example, are C3
  plants.)C4 plants include such crop plants as
  sugar cane and corn. They are the second most
  prevalent photosynthetic type.

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C4 Plants

• Over 8000 species of angiosperms, scattered among
  18 different families, have developed adaptations
  which minimize the losses to photorespiration.
• They all use a supplementary method of CO2 uptake
  which forms a 4-carbon molecule instead of the
  two 3-carbon molecules of the Calvin cycle. Hence
  these plants are called C4 plants. (Plants that
  have only the Calvin cycle are thus C3 plants.)

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• Please check the following link for discussion of
  C3 and C4 and CAM plants
• Google Image Result for http//fig.cox.miami.edu/
  cmallery/150/phts/c10x19cam.jpg

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• C4 plants are well adapted to (and likely to be
  found in) habitats with
• high daytime temperatures
• intense sunlight.
• Some examples
• crabgrass
• corn (maize)
• sugarcane
• sorghum

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CAM Plants

• At night,
• CAM plants take in CO2 through their open stomata
  (they tend to have reduced numbers of them).
• The CO2 joins with PEP to form the 4-carbon
  oxaloacetic acid.
• This is converted to 4-carbon malic acid that
  accumulates during the night in the central
  vacuole of the cells.

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• In the morning,
• the stomata close (thus conserving moisture as
  well as reducing the inward diffusion of oxygen).
  
• The accumulated malic acid leaves the vacuole and
  is broken down to release CO2.
• The CO2 is taken up into the Calvin (C3) cycle.

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• These adaptations also enable their owners to
  thrive in conditions of
• high daytime temperatures
• intense sunlight
• low soil moisture.

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• Some examples of CAM plants
• cacti
• Bryophyllum
• the pineapple and all epiphytic bromeliads
• sedums
• the "ice plant" that grows in sandy parts of the
  scrub forest biome

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Comparison of Photosynthesis and Respiration
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Review

• Chapter Ten Extended Lecture Outline
• Chapter 10 eLearning Session