where do photosynthesis, light reactions, and sugar making reactions occur?
photosynthesis occurs in chloroplasts, mainly in leaf cells. The light reactions occur along the thylakoid membranes within the chloroplasts, where pigments capture light energy. The sugar-making reactions of the Calvin cycle occur in the stroma, the fluid between the inner membrane of the chloroplast and the thylakoids.
light is absorbed by chlorophyll molecules, exciting their electrons. The energy of excited electrons is then used to join ADP and phosphate to form ATP. NADP+ joins with excited electrons to form NADPH, which temporarily stores the energized electrons. In the process, water is split and oxygen is released.
energy from ATP, electrons from NADPH, and carbon from carbon dioxide are combined to produce sugar molecules.
light energy photosynthesis
light energy indirectly fuels ATP by powering transport of electrons (electron transport chain). The energy released during electron transport drives the movement of protons across a membrane (protein gradient) that fuels the production of ATP.
Peter Mitchell proposed that ATP synthesis is powered by the potential energy stored in a gradient of protons across a membrane; the flow of electrons through an electron transport chain generates a proton gradient that leads to the synthesis of ATP.
Jaganford and Uribe experiment
test chemiosmotic hypothesis by preparing chloroplast memb vesicles 1) grounding up leaves in small fragments 2) from these fragments extract membrane material that formed many tiny spherical vesicles Many of the vesicles were composed of peices of chloroplast membranes. Although not know at the time these vesicles contained the protein ATP synthase found in chloroplasts. 3) scientists prepared a solution of hydrogen ions adjusted ph 4 and the vesicles were placed in it 4) protons slowly crossed the membrane until the solution inside the vesicles was also pH 4 5) the solution outside because pH 8 by reducing proton concentration 6) ADP and inorg phosphate were also introduced and atp produced
true or false? The region of ATP synthase that catalyzes the production of ATP from ADP and inorganic phosphate spans the chloroplast membrane.
The region of ATP synthase that catalyzes ATP production protrudes out of, but does not span, the chloroplast membrane; the region that spans the membrane is an ion channel through which protons can pass.
Chloroplast membrane vesicles are equilibrated in a simple solution of pH 5. The solution is then adjusted to pH 8. Which of the following conclusions can be drawn from these experimental conditions?
ATP will not be produced because there is no ADP and inorganic phosphate in the solution.
Sunlight is a type of energy called radiation, or electromagnetic energy. Electromagnetic energy travels through space in a manner similar to the motion of waves in water.
the wavelengths that our eyes see as different colors--is only a small fraction of the spectrum.
pigments in chloroplast
Different pigments absorb light of different wavelengths. One pigment, chlorophyll a, absorbs mainly blue-violet and red light. This molecule participates directly in the light reactions. Another molecule, chlorophyll b, absorbs mainly blue and orange light. We do not see these absorbed colors when we look at a leaf. Instead, we see the green wavelengths that are reflected back from the leaf or transmitted through it.
light independent reaction
use ATP and NADPH to reduce CO2 from the atmosphere to sugar through set of reactions called Calvin cycle
light dependent reactions
occur in thylakoid membranes that contain an array of proteins and chlorophyl/ other pigments (photosystem) absorbs light and initiates the reactions 1) photosystem 1: excited electrons used to produce nadph 2) photosystem II used to produce ATP
oxygen gas released to environment
absorbs protons of light which bump electrons from chlorophyll molecules to electron acceptors. the chlorophyll molecules are oxidized. photosystem 2 transfers the energized electrons to a molecule called plastoquinone via an electron transport chain. the transfer releases enough energy to transport protons across the thylakoid membrane, a proton gradient forms with a higher concentration inside the thylakoid than outside
Which of the following statements best describes the relationship between the light-dependent and light-independent reactions of photosynthesis?
he light-dependent reactions produce ATP and NADPH, which are then used by the light-independent reactions.
iron containing compound that acts as the primary electron acceptor in photosystem; the passes electron off to a series of proteins to the cytochrome complex
Which of the following reactions ensures that the Calvin cycle can make a continuous supply of glucose?
Regneration of RuBP
_____ releases energy that is used to pump hydrogen ions from the stroma into the thylakoid compartment.
electron transport chain
Energized electrons from ____ enter an electron transport chain and are then used to reduce NADP+.
flow of electrons photosynthesis
Energized electrons from photosystem I are passed down an electron transport chain and added to NADP+ to form NADPH. Meanwhile, energized electrons from photosystem II are passed through another electron transport chain. Their energy is used to pump hydrogen ions (H+) from the stroma into the thylakoid compartment, creating a concentration gradient. Electrons leaving this electron transport chain enter photosystem I, replenishing its lost electrons. Photosystem II replenishes its electrons by splitting water. Hydrogen ions and oxygen are released into the thylakoid compartment. This is where the oxygen gas generated by photosynthesis comes from.
Engelmann was able to determine which wavelengths (colors) of light are most effective at driving photosynthesis with aerotactic bateria (O seeking)
First, Engelmann used a prism to disperse white light from the sun into the colors (wavelengths) of the visible spectrum.
Then, using a microscope, he illuminated a filament of green algae with the visible spectrum. The photosynthetic pigments in the alga absorbed some of the wavelengths of light, using the absorbed energy to drive the reactions of photosynthesis, including oxygen production.
Engelmann used his recently discovered aerotactic bacteria to determine which wavelengths of light caused the alga to photosynthesize most. Because the aerotactic bacteria were attracted to areas of highest oxygen concentration, they congregated around the regions of the alga that photosynthesized the most.
He then counted the bacteria associated with each region of the alga illuminated by the various colors of light.
Engelmann found that some wavelengths of light attracted more bacteria, suggesting that these wavelengths drive more photosynthesis than others.
What assumptions did Engelmann make in order to conclude that red and violet-blue light were more effective than green light in driving photosynthesis? Select the two that apply.
For Engelmann to be able to draw meaningful conclusions from his experiment, he had to assume that the number of bacteria at any location on the slide was proportional to the amount of oxygen produced by the alga at that location. If this were not the case, the distribution of the bacteria around the alga would be of no use in determining the amount of photosynthesis that occurs at each wavelength.
Similarly, it was necessary for Engelmann to assume that the distribution of chloroplasts among the cells in the algal filament was approximately equal. Fewer chloroplasts in one cell compared to another would mean a lower potential for oxygen production at any color.
Which red line shows the same action spectrum corrected for the unequal number of photons emitted across the visible spectrum?
Instead, the sun emits the most photons in the yellow part of the spectrum, with relatively fewer photons emitted in the red and violet-blue parts of the spectrum. Thus, the red and violet-blue regions of Engelmann's action spectrum were measured with fewer photons than in the yellow part of the spectrum.
requires input of energy? 1) Water to P680+
2) P680 to Pq (plastoquinone)
3) Pq to P700+
4) P700 to Fd (ferredoxin)
5) Fd to NADP+
1) no 2) yes 3) no 4) yes 5) no
How many carbon dioxide molecules must be added to RuBP to make a single molecule of glucose?
6 CO2 molecules are required to produce two G3P molecules, which can be combined to make one glucose molecule.
In the Calvin cycle, how many ATP molecules are required to regenerate RuBP from five G3P molecules?
CARBONS IN calvin cycle
To produce 1 molecule of G3P (which contains 3 carbons), the Calvin cycle must take up 3 molecules of CO2 (1 carbon atom each).
The 3 CO2 molecules are added to 3 RuBP molecules (which contain 15 total carbon atoms), next producing 6 molecules of 3-PGA (18 total carbon atoms).
In reducing 3-PGA to G3P (Phase 2), there is no addition or removal of carbon atoms.
At the end of Phase 2, 1 of the 6 G3P molecules is output from the cycle, removing 3 of the 18 carbons.
The remaining 5 G3P molecules (15 total carbon atoms) enter Phase 3, where they are converted to 3 molecules of R5P.
Finally, the R5P is converted to RuBP without the addition or loss of carbon atoms.
input/ output of light reactions
Input: Water, NADP+, ADP, light
Output: O2, NADPH, ATP
Neither: Glucose, CO2, G3P