Lecture 8: Photosynthesis II Flashcards

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1
Q

Noncyclic electron transport

A
  1. Electrons are supplied to system from the splitting of H2O by photosystem II, with release of O2, as a by-product. When photosystem II is activated by absorbing photons, electrons are passed along electron transport chain and are eventually donated to photosystem I
  2. Electrons in Photosystem I are “reenergized” by absorption of additional light energy and are passed to NADP+, forming NADPH
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2
Q

Cyclic electron transport

A
  • cyclic flow of electrons through Photosystem I and electron transport chain between PS1 and PS2
  • electrons are not passed to NADP+ but continuously cycled through PS1
  • water is not split
  • O2 is not produced
  • additional ATP is made
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3
Q

Proton accumulation in the thylakoid lumen:

Electrochemical gradient

A
  • “electro” generated by charge on protons
  • “chemical” arises from the acidified lumen resulting from proton build-up
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4
Q

Chemiosmosis

A
  • proton gradient established using the energy released during electron transport to run proton pump and photolysis of H2O
  • Protons flow through channel in ATP synthase complex providing energy to assemble ATP from ADP and Pi known as photophosphorylation
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5
Q

photophosphorylation

A
  • using light to add a phosphate group to something
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6
Q

summarize the events of light-dependent reactions of photosynthesis

A
  • photosynthesis and calvin cycle
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7
Q

carbon fixation

A
  • CO2 taken up from atmosphere and the carbon is incorported
  • Calvin cycle (C3 pathway)
    • most common pathway of carbon fixation, the reduction of carbon dioxide into simple sugars
    • uses energy stored in ATP and NADPH during light-dependent reactions to chemically fix CO2

- ATP and NADPH are used to run the calvin cycle

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8
Q

Light Compensation Point

A
  • the point at which photosynthetic gains match respiratory losses
  • AKA net CO2 exchange is zero
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9
Q

Light Saturation Point

A
  • the point at which you can add more light and you don’t see a big increasee in the photosynthetic rate
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10
Q

Photosynthetically Active Radiation (PAR) or Photosyntheti Photon Flux Density (PPFD)

A
  • measuring the visible light spectrum
  • x-axis
  • PAR - the wavelengths of light that can be used in photosynthesis
  • PPFD - the amount of usable light energy impinging upon a leaf per unit time
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11
Q

A

A
  • Assimilation Rate
  • units: micromoles/m2/s
  • rate at which CO2 is taken up by the leaf AKA CO2 uptake by leaf
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12
Q

Maximum rate of net photosynthesis

A
  • if you go over to the y-axis, at the LSP then this number is your maximum rate of net photosynthesis
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13
Q

Photosyntehtic rates and light environment

A
  • Canopy light levels high in early spring, low in mid-summer, and high again in autumn
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14
Q

Allium tricoccum

A
  • wild leek
  • spring ephemeral
  • aboveground leaves April-May
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15
Q

Viola pubescens

A
  • yellow violet
  • summer-green
  • abovegrund leaves May-September
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16
Q

Tiarella cordifolia

A
  • foam-flower
  • semi-evergreen
  • aboveground leaves mid-May thru mid-November
17
Q

Seasonal shifting of LCP

A
  • Allium - high & consistent LCP
  • Viola - LCP shifts downward from spring to summer
  • *Tiarella *- LCP shifts downward from spring to summer and upwards again in the fall