SBI4U - Chapter 3: Photosynthesis

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Oddishii
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SBI4U - Chapter 3: Photosynthesis
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2015-01-21 07:34:53
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  1. What two parts make up chlorophyll? Describe it
    Porphyrin - Mg atom surrounded by hydrocarbon ring with alternating single and double bonds. The electrons in these bonds absorb light energy and begin the photosynthetic process

    Phytol tail - hydrophobic, anchors molecule to membrane
  2. Significance of cyanobacteria?
    One of the firsdt cells to produce oxygn on a large scale and use sunlight in production of organic compounds from water and carbon dioxide
  3. True or false: in plants only leaves can photosynthesize
    true
  4. STRUCTURE AND FUNCTION: CUTICLE
    • Waxy
    • Protect the leaf from excessive absoprtion of light and evaporation of water
  5. STRUCTURE AND FUNCTION: EPIDERMIS
    Transparent, colourless

    Allows light to pass through mesophyll cells
  6. STRUCTURE AND FUNCTION: MESOPHYLL
    Spongy and palisade

    Photosynthetic cells that form the bulk of a leaf
  7. STRUCTURE AND FUNCTION: GUARD CELL
    Bean shaped around stoma

    Photosynthetic epidermal cells of a leaf or stem that GUARDS the size of an opening
  8. STRUCTURE AND FUNCTION: STOMATA
    Microscopic opening

    Openings on surface of leaf that allow the exchange of gas
  9. How much water will the average tree lose through stomata by transpiration?
    200 L
  10. How does transpiration help photosynthesis? (2)
    • Creates transpiration pull that helps move water, minerals, and other substances from roots to leaves
    • Produces an evaporative cooling system that prevents leaves from heating to temperatures that could inhibit or denature enzymes that catalyze the reactions of photosynthesis
  11. When would a leaf close their stomata?
    To maximize CO2 intake and limit water loss, any weather that promotes transpiration like sunny, warm, dry weather, will have guard cells reduce the size of stomata
  12. When guard cells are turgid (swollen), will stomata be open or closed?
    Open
  13. When guard cells are flaccid (limp), will stomata be open or closed?
    Closed
  14. How does the size of a guard cell change?
    When water moves in and out of cell; follows diffusion of potassium ions.

    Basically when K moves into guard cells, water follows, and guard cells swell, stoma open
  15. How does light affect the opening and closing of stomata?
    Sun come out, blue light activates blue receptors, making proton pumps pump protons out of cell = gradient

    Gradient makes K ions move, making water move, making guard cells swell, makinjg stomata open

    Simultaneously, mesophyll cells photosynthesize thus using CO2, making stomata open
  16. STRUCTURE AND FUNCTION: STROMA
    Protein rich semiliquid material

    Synthesis of photosynthesis
  17. STRUCTURE AND FUNCTION: THYLAKOIDS
    Interconnected flattened membrane sacs

    Separate compartment in stroma
  18. STRUCTURE AND FUNCTION: GRANA
    Stack of thylakoids
  19. STRUCTURE AND FUNCTION: LAMELLAE
    Thylakoid connectors

    Contains light-gathering pigment molecules and ETC
  20. Break down photosynthesis into three parts
    • Capture light energy
    • Use energy to make ATP and NADPH
    • Use free energy of ATP and NADPH to synthesize organic compounds from CO2
  21. Why is it wrong to call the Calvin cycle a dark reaction
    Enzymes that catalyze these reactions are activated by light and inactive in dark. Calvin Cycle also requires ATP and NADPH from light reactions
  22. What is a photosystem?
    Clusters of photosynthetic pigments embedded in thylakoid membranes of chloroplasts that absorb light energy. 

    Absorbed light energy goes in ADP, Pi, and NADP+ to make ATP and NADPH. The H shit is from water
  23. What is the difference between action spectrum and the absorption spectrum?
    An action spectrum is a graph illustrating effectiveness of wavelengths promoting photosynthesis; which wavelength is good for a specific pigment

    An absorption spectrum is a graph illustrating the wavelengths of light absorbed by pigments
  24. Differentiate between chlorophyll a and chlorophyll b
    • Chlorophyll A is the main bitch absorbing the energy of light to the carbon fixation reactions of photosynthesis, R group is CH3
    • Chlorophyll B is a side bitch accessory pigment absorbing things chlorophyll A cant, R group is CHO
  25. State other accessory pigments
    • Cartenoids - absorb light that can damage chlorophyll and lose energy as heat, orange
    • Xanthophylls - interspersed in thylakoid membranes, yellow
    • Anthocyanins - in plant cell vacuoles, not chloroplasts, red, violet, and blue
  26. Break down the light reactions into three parts
    • Photoexcitation: absorption of a photon by an electron of chlorophyll
    • Electron transport: transfer of excited electron thru series of membrane bound electron carriers = gradient = reduces an electron acceptor
    • Chemiosmosis: movement of protons through ATPase complexes to drive the phosphorylation of ADP and ATP
  27. STAGE ONE: CAPTURE LIGHT ENERGY
    Occurs in thylakoid membrane 

    Light is absorbed by photosystems -  first by PII then PI
  28. What are photosystems composed of?
    • Antenna complex
    • several hundred pigment molecules
    • absorb photons and transfers to rxn centre

    • Reaction centre
    • chlorophyll a molecule - energy trapped in here is sent to ETC

    Photon -> pigment -> pigment -> pigment -> chlorophyll a -> energy
  29. STAGE TWO: PRODUCING NADPH AND ATP
    Noncyclic electron flow

    TWO THINGS HAPPENING: ATP AND NADPH

    Excited e for PII moves through primary electron acceptor (pheophytin), e carriers (PQ, b6f, PC) and then ETC to replace an electron lost by photosystem I. This occurs twice

    Prior to, Z protein in PII splits water into H and G+ and electrons. One of these electrons are used to replace the missing e in PII. Oxygen is diffused out of cell, leaving protons in thylakoid space. These electrons will pass a proton pump called Q cycle to create an H+ gradient for chemiosmosis to photophosphorylate ADP to ATP. Four H+ per ATP per pair of e

    • e in PI is energized by photon
    • e goes to ferredoxin -> NADP reductase (to reduce to produce NADPH).
  30. What reaction transfers the excited e from chlorophyll to a primary electron acceptor?
    Redox
  31. Why do isolated chlorophyll molecules fluoresce?
    There is no primary electron acceptor to receive the photoexcited electron, so they are the primary light harvesting unit of the chloroplast
  32. List the series of e carriers in noncyclic e flow in order
    Plastoquinone, b6f-complex, and plastocyanin
  33. What is the primary electron acceptor?
    Pheophytin
  34. Which is which: PI, PII, P680, P700?
    • PI - P700
    • PII - P680
  35. What does the Z protein do?
    Z protein in PII splits water into H and G+ and electrons. One of these electrons are used to replace the missing e in PII
  36. Where does Z protein split water?
    Thylakoid lumen
  37. What is Cyclic Electron flow? Why does it occur?
    It is another way to produce energy using only PI. It makes ATP, but not NADPH, so it can be used when NADPH is high

    • Photon ejects e from PI 
    • e -> Fd erredoxin -> Q cycle -> b6f-complex (cytochrome chain) -> PI

    It creates the proton gradient for ATP
  38. True or false: PI is only used in cyclic electron flow
    True
  39. True or false: PII is only used in cyclic electron flow
    False, only PI
  40. True or false: ATP and NADPH is produced in Cyclic Electron Flow
    False; only ATP
  41. True or false: ATP and NADPH is produced in Noncyclic Electron Flow
    True
  42. If NADPH high, will cyclic of noncyclic occur?
    Cyclic
  43. If NADP high, will cyclic of noncyclic occur?
    Noncyclic
  44. STAGE 3: USING NADPH AND ATP TO SYNTHESIZE ORGANIC COMPOUNDS
    let's make some coco in da stroma

    dis all bout da CO2

    CO2 will be synthesized into carbs using energy from NADPH and ATP.

    1) Carbon Fixation

    CO2 is being added to 5-carbon molecule RuBP to make a 6-carbon shit, producing two 3-carbon shit (3 PGA). These reactions are catalyzed by rubisco
  45. Is Stage 3 cyclic or nah?
    ya
  46. Where does each stage of photosynthesis occur?
    • STAGE 1: Thylakoid membrane
    • STAGE 2: Thylakoid lumen
    • STAGE 3: Stroma of chloroplasts
  47. Name the three Calvin Cycle stages
    • Carbon fixation
    • Reduction Reaction
    • RuBP
  48. What percentage of rubisco make up the leaf?
    50%

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