Haziq's Photosynthesis (Chapter 10) Concept Review

Haziq’s Photosynthesis (Chapter 10) Concept Review! Answer Key. Don’t look at this until you’ve attempted to answer everything by yourself. 1.) What is a photoautotroph? What is a Heterotroph? Photoautotroph: organisms that produce their own energy through process of photosynthesis Heterotrophs: organisms that cannot produce their own energy, so they consume other organisms for energy. 2.) Gas exchange in plants occurs through pores called the ______. Stomata 3.) What’s one reason that the pores mentioned in number 2 are on the under side of the leaf rather than the top? One reason for doing this is to avoid dehydration. With the pores facing the top side, there is a greater chance of water loss when the pores open for gas exchange. I.e. water gas may escape the pores more readily if they face up. This is a water-conservation mechanism 4.) What are the reactants of Photosynthesis? Carbon Dioxide and Water 5.) What are the products of photosynthesis? Glucose and Oxygen 6.) Oxidation is the _______ of electrons while reduction is the ______ of electrons. Oxidation is the LOSS of electrons, while reduction is the GAIN of electrons 7.) Which has the longer wavelength: Blue vs Red Red 8.) Which has the higher energy: Blue vs Red Blue because it has higher frequency which correlates with higher energy 9.) Why do most plants appear green? Chlorophyll absorbs wavelengths except for those around the green area of the color spectrum. Therefore, chlorophyll appears green. There are lots of chlorophyll in plants, so plants appear green. 10.) Why do leaves change colors during the fall? There is a reduction of chlorophyll in the leaves of plants in the fall. This results in a reduction of green color. The reason the falling leaves are various colors in the fall is because of the leftover pigments (such as carotene). 11.) What color do you think a plant at the bottom of the ocean, where there is not very much light, would be compared to the color of a plant on ground or at the surface of the water. A plant at the bottom of the ocean would likely be a darker color, close to black, compared to a terrestrial plant. This is because at the bottom of the ocean, light is sparse and so the plant will have many different types of pigments to grab all the light it can get its hands on. If the plant is absorbing all the light coming its way, there’s little light left to reflect, so it appears black/dark. 12.) Generally speaking, plants exposed to less light have less pigments to absorb light. True or False? False. Refer to 11 for explanation. 13.)What are three types of energy transfer in photosynthesis? Describe each 1.) Fluorescence – After light excites an electron it drops back to an unexcited state, but not before releasing heat and light 2.) Resonance – After light excites an electron in a given pigment, the energy of the electron is transferred to a neighboring pigment. (this happens until the energy reaches the main reaction center). 3.) Reduction/Oxidation – After reaching the reaction center via resonance between surrounding pigments, this energy results in an electron transfer from the reaction center to some other compound. Such reactions are important because they will ultimately result in the transformation of NADP+ to NADPH at the end of the light reactions. *Look at the slides for a helpful visual* 14.)What are the two main products of the light reactions? The two main products that plants care about that are ATP and NADPH. Both of these are made from the light reactions. A byproduct of the light reactions that other living organisms care about that is produced is oxygen. So, in total, the light reactions product 2 main products and 1 by product. Know all three. 15.)Where do the light reactions occur? Thylakoid Membrane 16.)Where does the Calvin cycle occur? Stroma 17.)What are the three main components/structures in the thylakoid membrane that allow for the light reactions to occur? Photosystem II, Photosystem I, and ATP synthase. The photosystems are a means to transfer electrons and pump hydrogens outside of the thylakoid. This sets up ATP synthase to produce ATP using the electrochemical gradient. Think ATP synthase as a water-wheel: as the protons that were pumped out come back into the thylakoid through ATP synthase, imagine the protons as water and the ATP synthase as the water wheel. The water moves the water wheel and this produces energy – similarly the proton flow moves the ATP synthase and this creates energy in the form of ATP. 18.) Photosystem 2 was the first of the two photosystems to be discovered. True or False. False. Photosystem 1 was the first to be discovered. Though, photosystem 2 acts before photosystem 1. 19.) Plants can produce ATP with only one photosystem if they must. True or False Yes. Some plants only have Photosystem 1. They can still produce ATP – refer to the slide regarding cyclic flow of electrons 20.) What is the ultimate goal of the Calvin cycle? The ultimate goal of the Calvin cycle is to create 2 G3P molecules which are transformed into glucose. The Calvin cycle uses ATP, NADPH, and CO2 to create glucose essentially. 21.) Why did professor Bell refer to Rubisco as “naughty?” Rubisco is an enzyme in the Calvin cycle which is supposed to react with CO2 to result in 2 G3Ps which will give the plant glucose. That’s what the plant wants Rubisco to do. However, Rubisco sometimes is dumb and reacts with O2 instead of CO2 and this process (called photorespiration) wastes energy and produces only 1 (instead of 2) G3Ps alongside byproducts of cellular respiration. 22.)If photosynthesis occurs, but plants do not open their stomata frequently enough, what happens to oxygen levels inside the plant? Does this affect quality of photosynthesis; i.e. does it hinder the glucose production? Oxygen is a byproduct of photosynthesis. So, more photosynthesis = more oxygen in the plant. If the oxygen is not released into the atmosphere frequently enough, it will build up in concentration within the plant. Lots of O2 means that the chances of Rubisco interacting with O2 go up. This leads to photorespiration, which as we discussed, is bad. Photorespiration gives us only 1 G3P instead of 2 for the same amount of energy – so glucose production is hindered. This is why gas exchange through the stomata is important. 23.)Differentiate Photorespiration from photosynthesis Photorespiration = Rubisco interacting with O2 to give half desired and half un-desired products. Specifically, to give 1 G3P along with H2O and CO2. Problem here is that this uses the same amount of energy it would take to produce 2 G3Ps (which is what we want because that will result in glucose) Photosynthesis = what we want to happen in plants. Relating to Rubisco, this implies that Rubisco interacts with CO2 and gives us 2 G3P. 24.)Which plants separate gas exchange and Calvin cycle spatially by having Calvin cycle run in the Bundle-sheath cells? C4 Plants (found in tropical areas) separate gas exchange and the Calvin cycle spatially to prevent Rubisco from screwing around with oxygen. 25.)How many thylakoids are in a chloroplast? There’s anywhere from 10-20 Thylakoids in a stack within a chloroplast. And, there are 10-100 stacks in a chloroplast. Therefore, there are anywhere from 100-2000 thylakoids in a given chloroplast. The more you know… 26.)Which plants separate gas exchange temporally? CAM plants often found in desert areas (hot and dry). They do gas exchange at night and run light reactions and Calvin cycle during the day – this prevents rubisco from getÝng the chance to interact with O2 because the plant stocked up on CO2 and got rid of O2 the night before.