3. (1.5 pt) MX1 is a novel chemical being considered for use as an herbicide. Wh

Question

3. (1.5 pt) MX1 is a novel chemical being considered for use as an herbicide. When sprayed on plants, it can enter mesophyll cells and accumulates to high levels in the stromal compartment of chloroplasts. Once in the stroma, each MX1 releases a proton (see below). H* Chloroplast stroma Would MX1 be an effective pesticide? Explain your answer by indicating what step(s)s of photosynthesis would be affected by MX1 and how this affectlead you to your answer. 4isatJnclass we discussed a drug called DNP. DNP has been used in the past as a weight loss drug, one that also had significant detrimental sideeftests Assuming that DNP can enter plant cells, would DNP be an effective herbicide? Justify your answer. red blood cells transport oxygen to cells). A common symptom of anemia is tiredness/lack of energy. Explain what the consequences are of anemia on cellular energy production. 6. (1.5 pt) A gardener is concerned that her greenhouse is getting too hot from too much light and seeks to shade her plants with colored translucent plastic sheets, the color of which allows passage of only that wavelength. What color should she use to reduce overall light energy, but still maximize plant growth? Justify your answer.

Explanation / Answer

Question 3:

A lipophilic compound that is slightly acidic and is able to liberate its proton can potentially act as an uncoupler by shuttling protons across a membrane. The transfer of proton across a thylakoid membrane gradient from thylakoid lumen to chloroplast stroma is perhaps responsible for its ability to uncouple the electron transport chain from ATP synthesis. Because a proton shuttle provides an alternative to the route through the ATP synthetase complex, the overall process of ATP synthesis is rendered less efficient.

Since compounds that can act as uncouplers in photosynthesis can perform the same activity in a mitchondria and produce same effect, it can be used as an effective pesticide as well.

Question 4:

DNP is able to carry protons across the membrane of mitochondria and reduce the membrane potential established across the inner mitochondial membrane, and is thus an uncoupler of electron transport chain and oxidative phosphorylation. It can also act the same way in a chloroplast reducing the gradient across a thylakoid membrane and reduce its efficiency of ATP synthesis. Therefore, it can act also as a herbicide.

Question 5:

Production of ATP is coupled to electron transport chain. As electrons are transported across various systems in the mitochondrial membrane, a proton gradient is estabilsed across the membrane and this gradient drives the ATP synthetase to produce ATP from ADP. This enzyme’s activity is therfore tightly linked to the establishment of the proton gradient and therefore the elctron transport. Because oxygen is the final recepient of the electrons, a deficiency of oxygen can slow down the elctron transport chain. This, in turn, slows down the prodcution of ATP. Depleted ATP levels in the cells is a consequence of reduced levels of oxygen. This is why in anemia, where the cells receive less oxygen because hemoglobin is unable to efficiently carry oxygen, we can expect one of the symptoms to be fatigue and tiredness.

Question 6:

Plants have different kinds of chlorophyll pigments. In general, they all absorb light in two ranges of wvelengths: 380 nm to 520 nm and 620 nm to 720 nm. The colours corresponding to these wavelengths are violet, blue, green and red. As long as the filters let in these lights, the photosynthesis of the plants will be unaffected. Infrared radiations (720 nm to 1000nm) of the light are also important for many of plant’s physiological processes and must not be filtered out either.

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