ch.7 photosynthesis saves the day Flashcards
What is Le Chatelier’s principle?
Le Chatelier’s principle: the idea of being able to force a reaction to reverse if we intervene and take a whole lot of its product made to start making it’s reactant
In glycolysis, the excess products of glycolysis will cause glycolysis to reverse production.
Why doesn’t making energy by photosynthesis completely solve the problem caused by glucose depletion?
The making of energy by photosynthesis doesn’t completely solve the problem caused by glucose depletion because photosynthesis only works when there’s sunlight (during the day). Within seconds of the sun’s disappearance, electron carrier of photosynthesis is shut down and protons will gradually leak into the cell and osmosis will begin to suck in water.
Explain how H2S-splitting photosynthesis simultaneously solves the energy and osmosis crises, at least while the sun shines
Osmosis crisis: electron carrier ejects protons from inside the cell to outside of the cell, which relieves osmotic stress caused by all the other large molecules
Energy crisis: When concentration of protons get too high due to the electron carrier pumping H+ out of the cell, the reverse proton pump will come into play by pumping protons back into the cell, converting ADP back into ATP to solve the energy crisis.
What pathway takes reducing power (NADH,FADH2), ATP and CO2 as its inputs? What is the main product of this pathway? And where does this product go?
The pathway that takes reducing powers as its inputs is reverse Krebs cycle. The main product is pyruvate that will be used in reverse glycolysis.
From last week’s lecture, know how to find two RNA molecules in NAD+.
look for sugar base and phosphate
Please make a sketch for (A) and (B) below. The sketch should show the process in a circle, placed appropriately within the cell. It should include all the inputs into that process and where they come from, as well as all outputs from that process and where they go. Note that these inputs and outputs will not be listed in the question! Thus, you should start practicing right away.
Proton pump solves the osmosis crisis (causes energy crisis).
Input: ATP (from primordial soup)
Output: ADP+Pi (made from proton pump and is used in glycolysis as input)
Please make a sketch for (A) and (B) below. The sketch should show the process in a circle, placed appropriately within the cell. It should include all the inputs into that process and where they come from, as well as all outputs from that process and where they go. Note that these inputs and outputs will not be listed in the question! Thus, you should start practicing right away.
Glycolysis (and fermentation) of glucose from primordial soup solves energy crisis (causes food crisis).
Input: 2ADP+Pi (from proton pump and used in glycolysis), glucose (from primordial soup and used in glycolysis), NAD+ (from fermentation and used in glycolysis)
Output: ATP (from glycolysis and used in proton pump), 2 pyruvate (from glycolysis and used in fermentation), NADH (from glycolysis and used in fermentation)
Be able to use Le Chatelier’s principle to explain how the evolution of photosynthesis alters the functioning of the H+ pump and glycolysis
The evolution of photosynthesis alters the functioning of the H+ pump and glycolysis because it allows their processes to go in reverse using Le Chatelier’s principle, in which we can intervene and reverse a reaction by using its products to make its reactants. So in proton pumps, we would take the H+ ions and push them back through the proton pump to make ATP. For glycolysis, we’d use its products (ATP, NADH, and pyruvate) to make its reactant (glucose).
Draw a sketch of a membrane oriented vertically with “Reducing Power” increasing in the vertical axis (label this) to describe in detail how H2S-splitting photosynthesis solves the osmosis problem. Use the words, chlorophyll, light, photon, electron, H2S, S, H+, electron carrier, reducing power, NADH, inside cell, outside cell, H+ gradient. Explicitly explain how photosynthesis relieves the osmosis problem.
Photons from light hits chlorophyll, which splits H2S into 2H++O+2e-. The 2e-‘s are then moved from the chlorophyll to an e- carrier. After, the e- carrier ejects an H+ ion from the inside of the cell to the outside of the cell, which relieves osmotic pressure inside the cell by creating a lower H+ gradient inside the cell. The e- carrier then delivers the 2e- to NAD+, which reduces it to NADH. The NADH then goes to glycolysis.
Draw a sketch of an entire cell that shows how photosynthesis solves the energy problem. Use the words, electron carrier, NAD+, NADH, H-gradient, original H+ pump, ADP, ATP, Krebs cycle in reverse, carbon fixation.
When the e- carrier takes the e-, it pumps a proton out of the cell, creating a higher H+ gradient out of the cell. This causes the H+ pump to go in reverse to make ATP from ADP that fuels reverse Krebs to make pyruvate using CO2 (carbon fixation). It also fuels reverse glycolysis to make glucose and reduces NADH to NAD+.
Describe how the cell makes food as a dividend of photosynthesis. Sketch the pathways and use the words, proton pump, ATP, electron carrier, reducing power, NADH, carbon fixation, carbohydrate, “reverse Krebs cycle”, glycolysis, and pyruvate in your narrative. Be sure to distinguish the different roles of reducing power and ATP as sources of energy during photosynthesis. Also be sure to make clear whether processes are going in forward or reverse mode (and do not forget arrow heads).
The cell makes food as a result of photosynthesis because when the e- carrier recieves its e- from the chlorophyll (H2S is oxidized to make 2H++O+2e-), it reduces NAD+ to NADH, which has a high reducing power, During the handoff of the e-, protons are ejected from the cell, causing a higher concentration of protons out of the cell. This allows H+ pump to go in reverse to make ATP. CO2 from the atmosphere is then taken in by reverse Krebs to make pyruvate using ATP from the proton pump to make bonds during carbon fixation (carbon fixation= CO2 to pyruvate) and the reducing power of NADH from the e- carrier. Then, reverse glycolysis can occur using the pyruvate to make glucose in the cell that will be stored and used at night, in which pyruvate is reduced to make glucose.
What would happen if a Martian (or a cell biologist!)…
a) darkens the cell, deploys an intracellular mechanism that continuously reduces all NAD+ to NADH, and injects into the cell superabundant pyruvate and ATP. What would happen and why? What chemical(s) would accumulate?.
Given a lot of pyruvate and ATP, we can use Le Chatelier’s principle to know that given the outputs of glycolysis, we can make glycolysis go in reverse to create its reactants. Also, with NAD+ all continuously being reduced to NADH means that there is no NAD+ in the cell. Therefore, with glycolysis going in reverse, NADH can be oxidized to NAD+. Lastly, there will be a lot of glucose building up since it’s the output of glycolysis in reverse as we all ADP+Pi since H+ pump is moving forward due to the huge supply of ATP.
What would happen if a Martian (or a cell biologist!)…
b) darkens the cell, deploys an intracellular mechanism that continuously oxidizes all NADH to
NAD+, and injects into the cell superabundant glucose. What would happen and why? What
chemical(s) would accumulate?
Since you are given a lot of glucose, which is the input of glycolysis, meaning glycolysis is going to occur. Also, with NADH constantly being oxidized, there is only NAD+ in the cell. This also shows that glycolysis is going forward. Lastly, there will be an excess amount of pyruvate since it’s the output of glycolysis.
If Krebs (forward) is being used, then CO2 is accumulating.
Describe with sketches the following:
a. the original function of the proton pump
b. its new function in the sunlight with photosynthesis.
In your two descriptions you must identify every input and where it came from, as well as every output and where it goes. Finally, for each function, identify the most important output, i.e., the primary function.
a: input: ATP (from primordial soup)
output: ADP+Pi (to glycolysis)
ADP+Pi is used to eject H+
b. input: ADP+Pi (from reverse glycolysis)
output: ATP (to reverse Krebs and to reverse glycolysis)
ATP used to make pyruvate and glucose
C. Chlorophyll, electron-carrier protein, and reversed proton pump (Le Chatelier) solves both
osmosis and energy crises in the daylight.
e- carrier solves osmosis crisis and reverse H+ pump solves energy crisis during the day
chlorophyll: e- from H2S
e- carrier: e- from chlorophyll
H+ pump: ATP from H+ pump to reverse Krebs and reverse glycolysis
ADP+Pi from reverse glycolysis
