Introductory Questions

1
Introductory Questions 8

• Where is the Casparian strip located?
• Why must plants use active transport in order to
  take in ions into the root hair cells?
• Name the two types of cells that make up the
  mesophyll layers in a leaf. What kind of tissue
  (cell types) are they?
• Briefly explain how the stomata open and close.
  Name the ions involved. What color light cause
  the stomata to open?
• Name three factors that can affect transpiration
  in plants.

2
Introductory Questions 10

• Name the three parts that make up a photosystem.
• How does NADPH differ from NADH?
• What does it mean when we FIX carbon? Does this
  happen in the light or dark reactions?
• What is required in order for the light reactions
  to proceed?
• How does non-cyclic photophosphorylation differ
  from cyclic photophosphorylation? Which process
  is more common?

3
Introductory Questions 11

• Name the three phases of the Calvin Cycle. Which
  phases require ATP and how much ATP would be
  needed for producing on glucose molecule?
• 2) What are the substrates that attach to the
  active sites of Rubisco?
• How does a C3 plant differ from a C4 plant? Give
  3 examples of a C3 C4 plant.
• What happens as a result of stomata closing?
• Which type of plant undergoes photorespiration?
  Does photorespiration occur at night or during
  the day? How is photorespiration different from
  cellular respiration seen in the mitochondria?
• How are C4 and CAM plants similar and how are
  they different? Give an example of both.

4
Chapter 10

• Chapter 10
• Photosynthesis
• The conversion of radiant energy into chemical
  energy
• Converting inorganic matter into organic matter

5
Overview of Chapter 10

• Autotrophs vs. Hetertrophs
• Properties and Characteristics of Light
• Chloroplast Structure Function Key Pigments
  Chlorophyll a b, Carotenoids
• Light Reactions (Light Dependent)-Photosystems
• Cyclic vs. Non-cyclic flow of Electrons
• Dark Reactions (Light independent)-Calvin Cycle
• Photorespiration ? Photosynthetic efficiency
• C3, C4, and CAM Metabolic Pathways of Plants

6
Photosynthesis in Nature

• Autotrophs are biotic Producers
• Ex. Photoautotrophs and chemoautotrophs
  obtains organic food without eating other
  organisms
• Heterotrophs are biotic Consumers obtains
  organic food by eating other organisms or their
  by-products (includes decomposers)

7
Properties of Light

• Electromagnetic Radiation
• Possesses properties of a particle and a wave
• Generated when electrons move from a high energy
  state to a lower energy state.
• Small portion of the EM spectrum (pg .157)
• Composed of small packets or quantized amount
  of energy called PHOTONS
• Described by Max Plank and DeBroglie

8
Visible Light

• Wavelength range of 380 nm 760 nm
• Colors include
• R O Y G B I V
• Red Lowest energy, Longest wavelength
• Violet Highest energy, smallest wavelength

9
Properties of Light (Pg. 186)
10
Photons and Electrons

• Photons interact with electrons and move
  electrons to higher energy levels from the
  ground state
• When electrons fall to the lower ground state,
  and light is emitted as it falls. This light is
  called Fluorescence.

11
Leaves The Solar Collectors for Plants

• Considered to be an organ of the plant
• Site for Photosynthesis (lots of chloroplasts)
• Cutin-thin wax layer helps to reduce or control
  water loss
• Other features worth noting
• -Upper Lower epidermis
• -Stomata Guard cells
• -Xylem Phloem (vascular bundle sheaths)
• -Palisade spongy Mesophyll
• -Trichomes
• High surface area Can cause water to be lost
• See a definite trade off

12
Cell Layers Observed in Leaves
13
The Chloroplast and Light (pg. 186)

• The (3) Fates of Light as it interacts with a
  chloroplast.

14
Introductory Questions 9

• How is an autotroph different from a heterotroph?
• Briefly explain what light is and how it is
  generated.
• In plant tissue, where are chloroplasts highly
  concentrated?
• 4) How are chloroplasts similar to mitochondria?
  How are they different?
• 5) How do plants absorb light energy? Name some
  features that allow plants to absorb light. What
  are some differences between chlorophyll a and
  chlorophyll b?
• What did Engelmanns experiment measure? What
  organisms did he use?
• Which reactant does the oxygen produced from
  photosynthesis directly come from?
• Where specifically do the light and dark reaction
  take place within a plant cell?

15
Overview of Chapter 10

• Autotrophs vs. Hetertrophs
• Properties and Characteristics of Light
• Chloroplast Structure Function Key Pigments
  Chlorophyll a b, Carotenoids
• Light Reactions (Light Dependent)-Photosystems
• Cyclic vs. Non-cyclic flow of Electrons
• --------------------------------------------------
  -----------------------------
• Dark Reactions (Light independent)-Calvin Cycle
• Photorespiration ? Photosynthetic efficiency
• C3, C4, and CAM Metabolic Pathways of Plants

16
The Leaf The Site for Photosynthesis
17
Structure of the Chloroplast

• Double membrane
• Has its own DNA
• Internal membrane system called Thylakoids
• Contains protein pigmets ex chlorophyll a

18
Typical Pigments Found in the Thylakoid Membrane

• Chlorophyll a - important in light reactions
• Chlorophyll b - accessory pigment
• - has a yellow/green reflection
• Carotenoids are yellow orange
• Anthocyanins are red pigments
• Fucoxanthin is a brown pigment
• Xanthophylls are typically yellow

19
The Chlorophyll Molecule (Pg. 188)

• Porphyrin ring
• (absorbs light)
• Central Magnesium Atom
• Hydrocarbon tail
• Alternating double single bonds
• Similar to hemoglobin
• History of Discovering Chlorophyll
  http//www.chm.bris.ac.uk/motm/chlorophyll/chlorop
  hyll_h.htm

20
Determining Absorbance of a Pigment (pg. 187)
21
Absorption Action Spectra (pg. 187)
22
Engelmanns Experiment (pg. 187)

• Obtained the first action spectrum in 1883
• Used Spirogyra w/spiral shaped chloroplasts
• Exposed this alga to a color spectrum using a
  prism
• Measured photosynthesis by using certain motile
  bacteria that would be attracted to the oxygen
  released by photosynthesis.
• Control Ensure that the bacteria were not
  attracted to the colors, he conducted the
  experiment without spirogyra. No preference was
  shown by the bacteria.

23
Discovering the Process of Photosynthesis

• For centuries gardeners have asked the perplexing
  question
• Where does the mass of a tree that weighs
  several tons come from when it starts as a
  seedling weighing only a few grams?
• Does it come from
• -Soil
• -air
• -water

24
Experiments conducted probing this Question

• Jan Van Helmont - accounted for the water
  (hydrate) aspect of photosynthesis
• Joseph Priestly accounted for the release of
  oxygen by photosynthesis using a a burning
  candle, glass jar and a mint leaf.
• Jan Ingenhousz same as Priestly except showed
  that light was required.

25
Photosynthesis Equation
26
Photosynthesis-Chemical Equation

• Reactants carbon dioxide water
• Products Glucose and oxygen gas
• Also Light energy, enzymes, pigments

27
Another Perplexing Question about Photosynthesis

• Where does the oxygen released by photosynthesis
  come from directly? Does it come from the carbon
  dioxide or water?
• First challenged by Challenged by C.B. Van Niel
  using photosynthetic bacteria which showed that
  CO2 is not split.
• Isotopic Oxygen (18O) was used to trace and track
  the fate of oxygen.

28
Tracking the Fate of Isotopic Oxygen
29
Photosynthesis an overview

• Redox process
• H2O is split into
• 2e- and 4 H
• The Hs are transferred to CO2 and a sugar is
  produced (CH2O)
• 2 Major steps to Photosynthesis
• Light Reactions (photo)
• -occurs in the thylakoids
• Dark Reactions
• -Also called Carbon fixation
• -occurs in the stroma
• -Involves the Calvin Cycle

30
Photosynthesis an overview
31
A Photosystem

• Light Harvesting Pigments
• Have antennae pigments complexes
• (200-300 pigment molecules)
• Chlorophyll a and chlorophyll b are present
• Chlorophyll a Reaction Center
• Primary Electron Acceptor will receive the
  electron (reduced) and chlorophyll a will be
  oxidized and lose the electron.

32
Structure of a Photosystem

• Light harvesting units of the thylakoid membrane
• Composed mainly of protein and pigment antenna
  complexes
• Antenna pigment molecules are struck by photons
• Energy is passed to reaction centers (redox
  location)
• Excited e- from chlorophyll is trapped by a
  primary e- acceptor

33
Photosystems in the Thylakoid Membrane
34
Mechanical view of Photosynthesis
35
Noncyclic Electron Flow

• Most common light reaction pathway
• Involves (2) Photosystems
• Photosystem II (P680)
• Photosystem I (P700)
• Exhibits A Z scheme or Zig-Zag flow of
  electrons
• Electrons flow in one direction
• ATP and NADPH are produced
• Electrons do not cycle back to the ground state
  to chlorophyll.

36
Photosystems in the Thylakoid Membrane
37
Noncyclic Electron Flow
38
Build up of Hydrogen ions in the thylakoid space
39
Cyclic Flow of Electrons

• Utilizes Photosystem I (P700) only
• Electrons cycle back to chlorophyll
• NADPH is not produced.
• Helps to produce more ATP that is used in the
  Calvin Cycle
• Stimulated by the accumulation of NADPH

40
Cyclic Electron flow

• Alternative cycle when ATP is deficient
• Photosystem I used but not II produces ATP but
  no NADPH
• Why? The Calvin cycle consumes more ATP than
  NADPH.
• Cyclic photophosphorylation
• Review of Light reactions
• http//web.mit.edu/esgbio/www/ps/light.html

41
Cyclic Electron flow
42
Photosynthesis-Light Dark Reactions
43
The Calvin Cycle-C3 pathway

• 3 molecules of CO2 are fixed into
  glyceraldehyde 3-phosphate (G3P)
• 3 Phases
• 1- Carbon fixation
• Each CO2 is attached to RuBP (rubisco enzyme)
• 2- Reduction
• electrons from NADPH reduces to G3P ATP used up
  
• 3- Regeneration
• G3P rearranged to RuBP ATP used cycle
  continues

44
The Calvin Cycle-C3 pathway
45
Calvin Cycle First Phase

• Carbon Fixation
• (1 carbon) (5 carbon) (3 carbon)
• CO2 Ribulose Bisphosphate (RuBP) ?2
  Phosphoglycerate (PGA)
• w/ help of RUBISCO
• (Ribulose Bisphosphate Carboxylase)-most abundant
  protein on earth
• Carbon is converted from an inorganic form into
  an organic form and thereby FIXED.
• A Total of Six carbons must be fixed for one
  glucose molecule or some other hexose.

46
Calvin Cycle Second Phase

• Reduction Phase
• Phosphoglycerate (PGA)
• ? is phosphorylated (use ATP)
• 1,3-bisphosphoglycerate
• ? Redox Rxn w/NADPH
• Glyceraldehyde-3-Phosphate (G3P)
• G3P is a sugar also seen in glycolysis
• For every 3 CO2 ? 6 G3P is produced but only ONE
  can be counted as a gain in carbohydrate and can
  exit the cycle.

47
Calvin Cycle Third Phase

• Regeneration of RUBP
• 5 G3P are phosphorylated ? 3 RuBP
• 3 ATPs are used to do the chemical rearrangement
• RuBP can now accept more CO2 molecules

48
Calvin Cycle - Net Synthesis

• For every G3P molecule produced
• 3 CO2 are brought in
• 9 ATPs are consumed
• 6 NADPH are used
• G3P can then be used by the plant to make
  glucose and other organic compounds
• Website for review of the Calvin Cycle
  http//web.mit.edu/esgbio/www/ps/dark.html

49
To Make a Six Carbon Molecule You need

• 6 CO2 molecules (6 carbons)
• 6 molecules of RuBP (30 carbons)
• (remain in the cycle from TEN G3Ps)
• 18 ATP molecules
• -Produced-
• 12 molecules of PGA (36 carbons)
• 2 molecules of G3P (6 carbons)

50
C3 Metabolic Pathway in Plants

• CO2 enters directly into the Calvin Cycle
• The first organic compound made is a 3 carbon
  molecule called PGA (phosphoglycerate)
• Close their stomata on hot, dry days to conserve
  water.
• Photorespiration occurs typically in these
  plants.
• Examples include Rice, Wheat, and Soybeans.

51
Photorespiration

• Observed in C3 plants when stomata are closed
  during hot, dry days
• CO2 levels ? O2 levels ?
• Rubisco binds with O2 instead of CO2
• Drains the Calvin cycle (? photosynthetic output)
• No ATP is produced
• No food molecules (G3P) are made
• Thought to be an evolutionary relic (Rubiscos
  affintiy for O2 remains)
• Considered to be wasteful and no benefit known
• TWO Adaptations have emerged to minimize
  photorespiration They are observed in the C4 and
  CAM plants

52
C4 Metaboic Pathway in Plants

• CO2 and PEP (phosphoenolpyruvate) combine to
  produce a 4-Carbon compound called
  Oxaloacetate
• Unique anatomy is present w/Bundle Sheath cells
  that are photosynthetic surrounding the veins of
  the leaf.
• Calvin cycle is confined to the chloroplasts
  within the bundle sheath cells.
• PEP carboxylase is used intially instead of
  Rubisco (higher affinity for CO2)
• A high CO2 concentration is maintained for the
  Calvin cycle which minimizes photorespiration.
• CO2 is continually fed into the Calvin cycle from
  the mesophyll cells even when the stomata are
  closed.
• Examples include Corn Sugarcane

53
Cell Layers Observed in Leaves
54
Unique Anatomy of C4 Plants
55
CAM Plants

• CAM Crassulacean Acid Metabolism
• Adapted in arid environments
• Close their stomata during the day and open them
  only at night. (reverse of typical plants)
• Organic compounds made are stored at night in
  their vacuoles when the stomata are open then
  used later during the day.
• Common in succulent plants such as ice plants,
  pineapple and cacti.

56
Comparing CAM and C4 Plants
57
A Review of Photosynthesis
58
Review of Key PointsPhotons ? Food

• Light Reactions ? ATP and NADPH
• Calvin Cycle ? Sugar Fixes CO2
• The sugar produced supplies the plant w/chemical
  energy carbon skeletons needed for other
  cellular parts.
• 50 of the sugar produced is used for cellular
  respiration in the plants mitochondria.
• Typically, plants produce more organic material
  than they need and store it away as starch.

59
Content Breakdown for Test 1

• Topic Questions
• Chapter 20 Origin of the Earth 4
• Chapter 26 Bryophytes Ferns 4
• Chapter 27 Gynosperms Angiosperms 4
• Chapter 35 Lifecycle of Angiosperms Fruit 8
• Chapter 36 Hormonal responses 3
• Chapter 31 Tissues 4
• Chapter 33 Stems 8
• Chapter 34 Roots 10
• Chapter 32 Leaves 8
• Chapter 8 Photosynthesis 12
• Cumulative (1st Semester content) 10

60
Controlling Stomata Activity

• Typically open during the day and closed at night
  (except in CAM plants) for CO2
• Two Guard Cells that surround the opening change
  their shape when H2O enters and leaves.
  (osmotically)
• Yellow pigments are thought be abundant in the
  guard cells which absorb Blue light.
• Uptake of potassium chloride ions OPENS the
  stomata
• (driven by actively transporting H ions out
  of guard cells)
• Decrease in sucrose concentration CLOSES the
  stomata
• Low CO2 stomata open High CO2 Stomata close
• Dehydration
• Circadian rhythms also contribute

61
Transpiration in Plants

• Loss of water by evaporation
• Cuticle helps to reduce this loss (1-3)
• Occurs mostly through open stomata
• Light, higher temperatures, wind, and dry air all
  increase transpiration
• Decreased by high humidity
• Can prevent plants from overheating
• Responsible for water movement in plants (to
  leaves)
• Distributes minerals throughout the plant
• Important part of the hydrologic cycle

62
Review of Key PointsPhotons ? Food

• Light Reactions ? ATP and NADPH
• Calvin Cycle ? Sugar Fixes CO2
• The sugar produced supplies the plant w/chemical
  energy carbon skeletons needed for other
  cellular parts.
• 50 of the sugar produced is used for cellular
  respiration in the plants mitochondria.
• Typically, plants produce more organic material
  than they need and store it away as starch.

63
Stomata Opening and Closing
64
Controlling Stomata Activity

• Typically open during the day and closed at night
  (except in CAM plants) for CO2
• Two Guard Cells that surround the opening change
  their shape when H2O enters and leaves.
  (osmotically)
• Yellow pigments are thought be abundant in the
  guard cells which absorb Blue light.
• Uptake of potassium chloride ions OPENS the
  stomata
• (driven by actively transporting H ions out
  of guard cells)
• Decrease in sucrose concentration CLOSES the
  stomata
• Low CO2 stomata open High CO2 Stomata close
• Dehydration
• Circadian rhythms also contribute

65
Transpiration in Plants

• Loss of water by evaporation
• Cuticle helps to reduce this loss (1-3)
• Occurs mostly through open stomata
• Light, higher temperatures, wind, and dry air all
  increase transpiration
• Decreased by high humidity
• Can prevent plants from overheating
• Responsible for water movement in plants (to
  leaves)
• Distributes minerals throughout the plant
• Important part of the hydrologic cycle

66
Leaf Morphology
67
Leaf Morphology-Chapter 32

• Leaves can be used to identify different species
  of plants.
• (3) Characteristics are used
• Simple vs. Compound Leaves (Pinnate or Palmate)
• Leaf arrangement on the stem
• (alternate, whorled, or opposite)
• Venation Pattern (parallel, branched)