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PLS 002 MT 2
Flashcards to help study for Midterm 2 in PLS 002.
| Question | Answer |
|---|---|
| Why do different isotopes of the same element have similar chemistry? | They are the same element, so despite having different amounts of neutrons, they have the same number of protons, but reactions just might happen at different rates since they have different weights. |
| covalent bonds | nuclei share electrons |
| ionic bonds | interactions between charged molecules |
| hydrogen bonds | interactions between polar molecules |
| What do vertices, intersections, and blank line edges represent in molecular structures? | Carbon atoms |
| Where are the invisible hydrogen bonds in a molecular structure? | Coming out of the intersections |
| What does pressure represent? | energy per volume |
| What does temperature represent? | energy per particle |
| What is the relevance of Gibbs free energy in chemistry? | It's what determines the direction of spontaneous change in a chemical system. |
| Where does most of the energy enter the Calvin cycle? | Between 2 PGA and 2 PGal. |
| What molecule delivers energized electrons into the Calvin cycle? | NADPH |
| Why is Rubisco notable, compared to other proteins? | It's the most abundant protein on Earth, the most abundant protein in leaves, and the biggest reason crops need Nitrogen. |
| What is the ultimate source of the electrons that end up reducing the products of CO2 fixation in the Calvin cycle? | NADPH is an approximate source, but in light reactions, it's water. |
| Suppose the leaf's stomata close, shutting off the supply of CO2 to the Calvin cycle. Would you expect the NADPH concentration to increase or decrease? | The products of the CO2 fixation reaction (PGA) consume NADPH, so if you don't have any of those products, you'd be left with an increased concentration of NADPH. |
| Suppose the leaf's stomata close, shutting off the supply of CO2 to the Calvin cycle. Would you expect the NADP+ concentration to increase or decrease? | This would increase the concentration of NADPH (the reduced-form NADP skeletons of NADP+), so the concentration of NADP+ will decrease. |
| Suppose the leaf's stomata close, shutting off the supply of CO2 to the Calvin cycle. Would you expect the RuBP concentration to increase or decrease? | This would limit carbon dioxide intake, which would decrease the rate of photosynthesis, which would decrease the amount of RuBP that is converted to glucose, which would increase the concentration of RuBP. |
| What is the most quantitatively important reason that plants need water? | to replace water lost via transpiration |
| Where does the negative pressure of water in the xylem originate? | surface tension at the liquid-air interface in cell walls (the small openings where water evaporates and leaves) |
| Which type of transport (diffusion or bulk transport) causes long-distance water movement in the xylem? | bulk flow |
| Which type of transport (diffusion or bulk transport) causes very short-distance water movement in the xylem? | diffusion |
| What initially happens to the water potential in a cell if the concentration of potassium ions (K+) in the cell increases? | The water is diluted with potassium ions, so the water concentration decreases, which means that its chemical potential decreases, and therefore water potential decreases. |
| If the concentration of potassium ions (K+) in a cell increased, would you predict that water would flow into the cell or out of the cell as a result? | Into the cell in order to dilute the water-potassium solution and balance osmotic pressure (water will diffuse, moving from high water concentration to low water concentration). |
| If the concentration of potassium ions (K+) in a cell decreased, would you predict that water would flow into the cell or out of the cell as a result? | Out of the cell in order to increase the potassium concentration in the water-potassium solution and balance osmotic pressure (water will diffuse, moving from high water concentration to low water concentration). |
| What is the functional significance of the Casparian strip in roots? | It forces water (or solution) to cross membranes. |
| What would happen to the pressure in the xylem of a plant if the stomata in its leaves opened, after initially being closed? | It would decrease (become more negative), because you've started the flow that's pulling water through the xylem. There is stronger surface pressure at evaporation sites (because transpiration is faster). |
| What would happen to the pressure in the xylem of a plant if the stomata in its leaves closed, after initially being open? | It would increase (become less negative), because you've stopped the flow that's pulling water through the xylem. There is weaker surface pressure at evaporation sites (because transpiration is slower). |
| What are the consequences of RuBP oxygenation? | In addition to PGA, phosphoglycolate is also produced, which isn't useful to the Calvin cycle, so some or all of the carbon and energy in that molecule is lost. |
| By what percentage does photorespiration reduce net photosynthesis in typical conditions (25 degrees Celsius in a C3 plant)? | About 25% |
| How does temperature influence the rate of photorespiration, and why? | Warming decreases the solubility of both CO2 and O2 (primarily of CO2), which increases the rate of photorespiration. |
| Where is CO2 initially fixed from the atmosphere in C4 plants? | In the mesophyll cells |
| Where is Rubisco located in C4 plants? | In the bundle sheath cells |
| Under what environmental conditions is C4 photosynthesis better than C3 photosynthesis? | warm and sunny |
| True or false: the initial fixation of carbon dioxide from the atmosphere in photosynthesis and the carboxylation of RuBP are separated temporally in C4 plants. | False, the initial fixation of CO2 from the atmosphere in photosynthesis and the carboxylation of RuBP are separated spatially in C4 plants. |
| What are the ultimate electron donor and acceptor in aerobic respiration? | The ultimate donor is carbohydrate and the ultimate acceptor is oxygen. |
| What are the ultimate electron donor and acceptor in photosynthesis? | The ultimate donor is water and the ultimate acceptor is carbon dioxide. |
| How many CO2 molecules are released directly from the TCA cycle for every "turn" of the cycle? | Two |
| Alpha-ketoglutarate (α-KG) is one of the members of the TCA cycle. How many molecules of α-KG are consumed for every glucose molecule that is fully oxidized? | Zero |
| In which phase of aerobic respiration is most of the ATP generated? | In the oxidative phosphorylation phase |
| In which phase of anaerobic respiration is most of the ATP generated? | In the glycolysis phase |
| Where do the electrons end up in anaerobic respiration? | They end up in the last carbon product (ethanol or lactate). |
| Suppose a leaf is synthesizing a lot of fatty acids, which are assembled from acetyl-CoA as a precursor. How would you expect this to affect the amount of NADH produced per molecule of glucose in respiration? | This would decrease the amount of NADH produced per glucose molecule. |
| What are the essential macronutrients for plants? | Sulfur (S), Nitrogen (N), Calcium (Ca), Phosphorous (P), Potassium (K), and Magnesium (Mg). |
| Why don't most mineral nutrients passively diffuse across plant cell membranes? | They are charged and cannot cross the lipid bilayer. |
| What are the three major causes of soil acidity? | Net uptake of positive ions, net uptake of ammonium, and soil respiration |
| How does ammonium uptake affect soil pH? | It decreases soil pH, since this is one of the causes of soil acidity. |
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