Term
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Definition
All organisms require a constant input of energy to offset entropy
Capable of carrying out metabolism from external energy sources to carry out lifes processes (survival, reproduction, etc) |
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Term
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Definition
Heat loss, 2nd law of thermodynamics.
Without constant energy, organisms would fall apart. |
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Term
| What two major metabolic pathways used to acquire energy? |
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Definition
| Respiration and Photosynthesis |
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Term
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Definition
Carried out by heterotrophs (cannot use energy from sun)
Convert chemical energy stored in complex molecules (sugars, carbohydrates, etc) to a form of chemical energy (ATP) that cells can use
Plants can respirate in the dark in the presence of oxygen. |
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Term
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Definition
Carried out by autotrophs
Convert light energy (sun) to chemical energy that is stored in bonds of complex molecules (sugars, carbohydrates, etc)
Light energy trapped by cells of photosynthesis, converted into ATP or NADH, energy then incorporated into the bonds of complex carbohydrates that are produced from the reduction of CO2.
plants, algae, cyanobacteria |
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Term
| Mesophyll cells of leaves |
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Definition
Two types, palisade (top of leaf) and spongy (bottom of leaf)
Most active photosynthetically active tissue
Flat, thin, ideal for gas exchange and trapping light
Contain numerous chloroplasts |
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Term
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Definition
| Contain specialized light-absorbing green pigments called chlorophyll |
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Term
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Definition
Main light trapping pigment
Specifically chlorophyll A (links all photosynthetic organisms together) |
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Definition
Tend to be packed in together
Surface of leaf (exposed to sunlight, loaded with chloroplast containing chlorophyll. |
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Term
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Definition
Suggests that the original photosynthetic pathway that was initially evolved in cyanobacteria has not been modified as it has moved into eukaryotic plants.
Supports the the theory that the chloroplasts seen in higher plants were absorbed by the ancestors of bacteria and not digested. |
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Term
| Photosynthetic pathway involves to broad reactions |
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Definition
| Thylakoid reactions and carbon fixation reactions |
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Term
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Definition
H20 + light energy -> O2 + ATP + NADPH
Slip water using electron transport chain
Transforms light energy in usable energy trapped in ATP and NADPH and H (proton)
Light dependent reactons |
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Term
| (Stroma) Carbon fixation reactions |
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Definition
CO2 + ATP + NADPH -> (CH2O)
Light independent reactions
Take energy in NADPH and ATP and put them into the bonds of carbohydrates
Reduce simple carbon compound (CO2) into a complex carbon compound (carbohydrate)
Bonds of carbohydrate hold energy from sunshine.
Now can be used for plants for their energy needs |
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Term
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Definition
| Liquid matrix inside chloroplast where Calvin Beson cycle carried out when carbohydrates are made from CO2 |
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Term
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Definition
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Term
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Definition
Light (energy source)
Water from soil and terrestrial environments
Water is oxidized becomes an electron donor, proton and electrons remain to carry out processes, release O2.
CO2 from air required for fixation to hold energy trapped by light. CO2 reduced. Overall redox reations |
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Term
| Pollution Event: Advent of O2 |
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Definition
Evolved by cyanobacteria was one of the first big pollution events. Changed atmosphere into oxidizing atmosphere.
Evolved by cyanobacteria. Little free oxygen to oxidizing atmosphere.
Sufficiently well done by cyanobacteria. Without free oxygen to support cell respiration, can't get enough energy out of carbohydrates to support metabolism.
-bacteria and yeast size biggest
Can get 36 ATP out of glucose instead of 2. |
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Term
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Definition
Carbohydrates (eg: sugars) stores chemical energy
Oxygen derived from water, not CO2. (Something that only photosynthetic organisms can do) |
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Term
| Chloroplast in higher plant cell or algae |
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Definition
Double unit membrane bound organelle
Interior has stroma matrix
Within stroma matrix has membranes stacked into structures called grana, each unit of a granum is called thylakoid |
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Term
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Definition
flat sack surrounded by membrane
Sometimes in stacks
Other regions will be single thylakoid connecting two stacks of thylakoids |
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Term
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Definition
Stacks of thylakoids
Membranes called lamelli
Thinner |
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Term
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Definition
| Thin thylakoid stacks joining grana together |
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Term
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Definition
When oxygen is a final product
Light energy converted into chemical energy by two different functional units
Photosystem I and Photosystem II
numbering system is by time discovered and not order they get used. PhotosystemII used first. |
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Term
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Definition
Wave and particle properties of electromagnetic energy
Long wavelengths have low energy
Short wavelengths have high energy
UV energy can damage photosystems
Amounts of energy referred to quanta
Delivered in packets of light called photons |
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Term
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Definition
Visible wavelength of light, 400nm to 700nm
Blue to red for photosynthesis
Photons impact pigments involved
Only a small amount of light that hits the surface of the earth is available to use based on chemistry of pigemnts
5% of light hiting earth is used for photosynthetic process (all life on earth) |
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Term
| Absorption pattern for Chlorophyll A and Chlorophyll B |
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Definition
Absorbs in blue (400-450) and red wavelengths (650-700nm)
Reflects green (500-550)
Chlorophyll B similar, shifted to the right. |
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Term
| Absorption pattern for Beta carotene |
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Definition
| Gives carrots orange colour. One of the pigments that absorb light |
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Term
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Definition
| Pigments work together to carry out general process. |
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Term
| Structure of Chlorophyll A and B |
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Definition
Like phospholipids (superficially).
Has head component that is hydrophillic and polar. Head pointed outward, where light will strike it.
Has a prophyrin-like ring structure with central Mg.
Ring contains some loosely bound electrons
hydrophobic fatty acid tail (anchors membrane in the thylakoid)
absorption maximum blue (430) and red 660nm)
Subtle changes in the functional groups of the head leads to different absorption patterns and pigments. Change methyl to CH0 Chlorophyll A to chlorophyll B (shifts absorption slightly.) |
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Term
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Definition
Beta carotenes can be involved in absorption of light
Accessory pigments
Photo-protective role
Maximum absorption at 400-500 nm
Have anti-oxidant properties to protect again light damage. |
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Term
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Definition
Accessory pigments
Optimal absorption at 500-600nm (pick up some green, reflect red)
Found in cyanobacteria |
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Term
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Definition
| Trap light energy. Main is chlorophyll. |
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Term
| Why are pigments there:Chlorophyll |
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Definition
Absorbs light photons which changes its energy state by altering distribution of electrons
Location of electron changes in the orbital of chlorophyll molecule
absorption of blue light excites chlorophyll molecule to higher energy state than absorption of red light.
Chl (ground state) + photon -> Chl* (excited sate, very unstable)
Electron moved to a higher orbital |
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Term
| Light absorption and chlorophll emmission |
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Definition
in unstable high energy state of, chlorophyll readily gives up energy as heat to surroundings
drops to a lower energy state
Four routs to dissipate energy form lowest excited state in order to return to stable ground state:
1)heat
2)re-emit photon of longer wavelength (fluorescence)
3)energy transfer to another molecule (resonance tranfer)
4)photochemistry (electron transfer) |
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Term
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Definition
Why evapotranspiration important
Leaves need air condition
Not useful to plants |
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Term
| Re-emit photon of longer wavelength (fluorescence) |
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Definition
Light released at lower wavelength, due to lost energy
Not useful to plants |
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Term
| Energy transfer to another molecule (resonance transfer) |
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Definition
Transferred to other pigment molecules
Not direct transfer of electrons, rather a transfer of energy.
One pigment virbates and the rest start vibrating at the same frequency |
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Term
| Photochemistry (electron transfer) |
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Definition
Most important. Transfer of excited electron to a chemical receiver.
Excited electron can then enter electron transport chain
Moved from light energy to chemical energy. |
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Term
| Photochemistry: Chlorophyll |
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Definition
Blue light has more energy than red.
When blue is absorbed, electron goes to highest excited states.
Red light excites electron to lower excitable range.
Either way, chlorophyll is unstable.
Some energy is lost as heat.
Ideally, excited electron goes into electron transport chain
If not an intact photosynthetic pathway, as electron falls back to ground state, it will release photon of light in much lower energy than absorbed (fluorescence) |
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Term
| Key Experiments of Photosynthesis:Joseph Priestley (1771) |
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Definition
Discovered O2 evolution in plants
Ex: A bell jar over a candle will flame out the candle, because all the oxygen will be used.
If plant put in the same bell jar with the candle that has flamed out, the candle can be relit, or if smoldering the flame will burst on, because presumably O2 is made by the plant. |
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Term
| Key Experiments of Photosynthesis: Jan Ingenhauz (1779) |
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Definition
Light essential in plants
Allowed the advent of the crude equation:
6CO2 + 6H2O --(light)--> C6H12O6 + 6O2
Not true reaction, just overall reaction. Requires multiple reactions. |
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Term
| Key Experiments of Photosynthesis: CB van Niel (1920s) |
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Definition
Showed redox reactions involved in photosynthetic pathways especially the light component.
This was crucial in the understanding of mechanisms in the plant |
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Term
| Joseph Priestley (1771) + Jan Ingenhauz (1779) + CB van Niel (1920s) |
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Definition
Reduction of CO2 (most highly oxidized form of carbon) to a fairly reduced C6H12O6 (sugar or starch)
Since these experiments, it has been established that photosynthesis is far more complex. At least 50 intermediate reactions. |
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Term
| Key Experiments of Photosynthesis: TW Engelman (1880s) |
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Definition
Used action spectra of photosynthesis to identify pigments
-helped find 2 distinct photosystems.
Established that wavelengths of light dictate how much photosynthesis can take place.
Grew algae (spiro gira, has spiral shaped chloroplast) in not azenic with bacteria) and looked at them under microscope. Shown spectrum of light on the spiral chloroplast, and looked at growth of aerobic (need oxygen) bacteria.
Found bacteria accumulated in areas of spectrum where blue and red light was. Where most active photosynthesis and oxygen production.
Action spectrum (oxygen production) and absorption spectrum (light induction) should be similar
Hinted to different photosystems: photosynthetic purple and green bacteria (use light) only have photosystem 1 working. Do not trap light to fix carbs. Instead do non cyclic photophosphorilation, the light is used to generate ATP only as supplement to glycolysis. |
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Term
| Key Experiments of Photosynthesis |
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Definition
| Photosynthesis occurs in light harvesting antennas (pigment molecules arranged in an antenna like structure surrounding a reaction center) associated with photochemical centers. |
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Term
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Definition
| Where conversion of light to chemical energy takes place. |
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Term
| How is light energy converted to chemical energy in antenna-reaction center complexes? |
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Definition
Most pigments in pro/eukaryotic cells serve as an antenna complex. Not directly related to transfer of chemical energy, rather are collecting devices. They transfer energy to one of two reaction centers associated with photosystems (either photo 1 or photo 2).
Series of redox reaction converts light energy to chemical energy. |
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Term
| How do plants benefit form division of labor between antenna pigments and reaction center pigment? |
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Definition
Even in bright sunlight, chlorophyll is limited in absorption ability (only absorb a few protons/second)
Therefore, with pigment having it's own action center is inefficient, because most of the time, action center would be idle.
Efficiency: Allows many pigments to be involved in the capture of light then reaction center is funneled the energy and allows the chemical reaction to move forward.
Multiple pigment molecules in the antenna molecule cooperate to collect steady supply of energy and focus energy on the reaction center to keep enzymes active.
Transfer of energy is through RESONANCE TRANSFER. No direct transfer of any matter. Vibrational energy is transferred and that energy is collected in the reaction center. That energy when build up is enough to move an electron into a higher energy orbital. |
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Term
| Basic Concept of Energy Transfer during Photosynthesis |
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Definition
| Light collected by pigment molecules (includes pigments other than chlorophyll) in the antenna complex (where vibrational energy transfer occurs). The collected energy is then moved to the REACTION CENTER (Where electron transfer occurs) |
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Term
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Definition
| Where electron transfer process occurs. Cycle of electron acceptor and donor. |
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Term
| Key Experiments of Photosynthesis: Roy Emerson and William Arnold (1932) |
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Definition
Looking at efficiency of the process converting light to chemical energy.
Showed the cooperation of many pigment molecules to carry out light trapping process in energy conversation during photosynthesis.
Exposed chlorella (alga) to short light flashes (10mircoseconds) of different intensity at 0.1s (least amount of time required for photosynthetic apparatus to recover and accept another photon) intervals.
-to measure amount of photosynthesis, they measure the amount of O2 being released.
Showed that that production of oxygen increases with increase in light intensity.
Curve on graph was a PI (Photosynthesis Intensity) curve (smooth positive curve. Less and less positive as light intensity increased). |
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Term
| Graph: Relationship of Oxygen Production to Flash Energy |
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Definition
-PI curve.
-Smooth positive curve. Less and less positive as light intensity increased
-Linear portion at low intensity
-Flat portion at high intensity
-Therefore, regardless of light intensity, the photosynthetic apparatus cannot be anymore efficient. The apparatus was saturated with light (high light intensity).
@Linear portion of curve: Light limited the production of energy.
@Flat region: Not light limited. Light component saturated, thus more light does not make the apparatus more efficient. Carbon limited section of curve. |
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Term
Key Experiments of Photosynthesis: Roy Emerson and William Arnold (1932)
-Explanation: Amount of Chlorophyll Used |
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Definition
Showed how many pigment molecules needed for oxygen production: 1 O2 molecule produced/2500 chlorophyll molecules
Why: Multiply pigment molecules in light capture.
1) Several hundred chlorophyll molecules associated with each reaction center (PS1 and PS2) for transfer of energy
2) Reaction center has to operate 4 times to generate 1 O2 molecule.
4(e-) + (4H+)--->2H20--->1O2
therefore approx 600chlorophyll/e- |
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Term
Key Experiments of Photosynthesis: Roy Emerson and William Arnold (1932)
-Explanation: Quantum Yield |
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Definition
Quantum Yield: (# of photochemicals produced)/(total number of light quanta absorbed)
Quantum Yield of chloroplast in dim light is approx 0.95
-95% of the quanta absorbed goes into the photosynthetic pathway.
-very efficient process.
Majority of excited chlorophyll |
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Term
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Definition
| Anything made by the plant using light energy, usually measure as the amount of oxygen used. Can also include CO2, etc. |
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Term
| Endergonic Process: Reduction of CO2 to (CH2O) |
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Definition
Very energy intensive process.
Equilibrium Constant = 10^(-500)
-under normal conditions the reaction would not occur (no spontaneous production of glucose).
Energy efficiency = (energy input)/(moles of O2 produced)
-Using red light, energy efficiency @ 27% |
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Term
| Key Experiments of Photosynthesis: Robert Hill (1937) |
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Definition
Demonstrated that reactions involved in the pathway of chemical conversation are redox reactions.
Took isolated chloroplast thylakoids and exposing them to light to see if they could reduce oxidized iron salts.
(Fe3+) + H2O ----> 4(Fe2+) + O2 + 4(H+)
Fe3+ high oxidized compound
H2O as source of electrons.
The iron was reduced by accepting electrons from the water. Very simliar to splitting water molecule to reduce chloroplast after excited stage when it received photon.
Showed O2 evolution occurs separately from CO2 reduction. In fact is occurs before CO2 reduction.
- Shows that O2 comes form H2O not CO2 (light dependent reaction and stroma reaction are two separate processes. |
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Term
| Key Experiments of Photosynthesis: Robert Emerson (1950s) |
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Definition
Looked at energy yields at different wavelengths. Is it consistent through the spectrum for chlorophyll but other pigments involved too.
Demonstrated that about 10 photons required to produce 1 molecule of O2
-Quantum yield for light absorbed constant, usually at around 10% (0.1) until green-greenish yellow (still around 10%, little lower). This is where accessory pigments involved.
until far-red light (Red Drop Effect). |
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Term
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Definition
Around 680 nanometers, efficiency drops dramatically. Wavelength is not efficient for photosynthetic processes.
Curious, because chlorophyll absorbs in the red, and also usually have accessory pigments to bring up efficiency. |
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Term
Key Experiments of Photosynthesis: Robert Emerson (1950s)
-Red and Far red combined. |
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Definition
Played around with red light itself.
If only far red light (700nm): photosynthesis really low.
If just red light (680): same range as far red.
When two wavelengths at the same time, then: maximized photosynthesis (EMERSON ENHANCEMENT EFFECT).
700 and 680 are wavelengths absorbed by the action centers. |
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Term
| Emerson Enhancement Effect |
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Definition
Rate of photosynthesis when red and far red light are given together is greater than the sum of the two rates when given apart.
Key: shows involvement of two photosystems.
-PS2: absorb @ 680
-PS1: absorb @ 700 |
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Term
| Summary of Key Experiments: |
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Definition
Energy Transformation
1)Quantum Yield =(number of photochemical products)/(total number of quanta absorbed)
-saturated at high light intensity (possibility of overloading system)
-in linear range (light limited): approx 8 to 10 quanta yield 1 O2 molecule or 8 photons of light (4 photons in PS1 and 4 in PS2).
2)Quantum efficiency (quantum yield) 95% of photos go into electron pathway. Very efficient.
3) Energy Efficiency(conversion): 27% of photons are captured in chemical energy, rest is lost in heat. |
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Term
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Definition
Semi autonomous organelles (have some of own DNA for specific photosynthesis protein synthesis and make their own organelle division)
-believed to be a bacterium that was originally engulfed.
-has characteristics of typical bacteria cell:
relatively small (5 to 10microm long and 2 to 4microm wide)
one circular chromosome
Arise from preexisting chloroplast or precursor proplastids (through fission) |
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Term
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Definition
| Double external membranes (all energy transfer happens on a different, third set of membranes: thylakoid membranes) |
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Term
Chloroplast: Membranes
1)Outer Membrane |
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Definition
-relatively permeable (sugars, ions)
-contains porins (channels like in bacterial cells)
-involved in ion transport
Not directly related to the photosynthetic light/energy extraction process |
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Term
Chloroplast: Membranes
2)inner membrane |
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Definition
-highly impermeable (maintain strict pH range in the stroma)
-require transporters
-involved in ion transport
Not directly related to the photosynthetic light/energy extraction process |
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Term
Chloroplast: Membranes
3)thylakoid membrane |
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Definition
All energy transfer action occurs here
-site of light reactions (where all the proteins involved in the electron transport chain are organized)
-contains integral proteins (transmembrane proteins that cross the membrane completely. Allows it to be a mechanism for moving protons from the stroma to the lumen)
-contains pigments |
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Term
| Reaction Centers in Membranes |
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Definition
Located in the membrane
Associated with antenna pigment-protein complex
-proteins have unique orientation:
assymmetrical:
animo group (N terminus found in the stroma)
Carboxyl group (C-terminus found in the lumen)
Allow electrons to move down electron chain from high energy to low energy (electron/proton differences)
Pigments associated with proteins to maximize light capture (no covalent bonds, loose associate, hydrophobic forces) |
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Term
| Organization and Structure of 4 Major Protein Complexes |
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Definition
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