Lecture 8: Photosynthesis II Flashcards
1
Q
Noncyclic electron transport
A
- 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
- Electrons in Photosystem I are “reenergized” by absorption of additional light energy and are passed to NADP+, forming NADPH
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
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
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
5
Q
photophosphorylation
A
- using light to add a phosphate group to something
6
Q
summarize the events of light-dependent reactions of photosynthesis
A
- photosynthesis and calvin cycle
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
8
Q
Light Compensation Point
A
- the point at which photosynthetic gains match respiratory losses
- AKA net CO2 exchange is zero
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
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
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
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
13
Q
Photosyntehtic rates and light environment
A
- Canopy light levels high in early spring, low in mid-summer, and high again in autumn
14
Q
Allium tricoccum
A
- wild leek
- spring ephemeral
- aboveground leaves April-May
15
Q
Viola pubescens
A
- yellow violet
- summer-green
- abovegrund leaves May-September