L08 GRQs - 8th GRQS UNC Chapel Hill Bio101 PDF

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8th GRQS UNC Chapel Hill Bio101...

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Phot os ynt hes i s Gui de dRe a di ngQs(Dot he s ebe f or et heMas t e r i ngAs s i gnme nt . ) ( Re adi ng7. 57 . 10 , 37 . 1 9and3 8. 4) Re adi ngobj ec t i ve s  De s c r i bet het wopar t sofphot os ynt he s i sa ndt hei nput sa ndout put sofbot hpa r t s .  Expl a i nwha tki ndofs unl i ghti sus e dbyt hepl a ntandwhys unl i ghti sne c e s s a r y .  Expl a i nphot ophos phor yl a t i oni nt hel i ghtr e ac t i onsofphot os ynt he s i s ,a ndde s c r i behow phot ophos phor yl a t i oni ss i mi l aranddi ffe r e ntf r om t heoxi da t i vephos phor yl a t i oni n a e r obi cr e s pi r a t i on. Before reading 7.5, draw a picture of the chloroplast and its membranes (see figure 7.2). the “anatomy” of the chloroplast is important to the process.

^^^Like mitochondria, chloroplasts also have an inner and outer membrane 1. Describe in words what happens in the light reaction of photosynthesis: Photosynthesis has 2 reactions: the light reaction, and the Calvin cycle **Light reactions: absorb solar energy and convert it to chemical energy, which is stored in both ATP and NADPH. -Light reactions occur in the thylakoids, and their main purpose is to convert light energy to chemical energy and release oxygen. -Inputs = light and water. Outputs = oxygen gas -Water is split which provides a source of electrons and gives off oxygen as a by product -Light energy is absorbed by chlorophyll molecules and built into the thylakoid membranes and this energy is used to drive the transfer of electrons from water to NADP+, reducing it to NADPH….

2. How is the Calvin cycle linked to the light reaction? NADPH from the end of the light reaction temporarily stores electrons and gives “reducing power” to the Calvin cycle. -Calvin cycle: occurs in stroma of the chloroplast, assembles sugar molecules using CO2 and the ATP and NADPH from the light reaction -Inputs: CO2 and ATP from light reaction and NADPH from light reaction -Outputs: sugar and NADP+ (recycled back into light reaction) and ADP + P (recycled back into light reaction) -uses carbon fixation (the incorporation of carbon from CO2 into organic compounds. Carbon fixation in the calvin cycle turns the carbons into sugars) -none of the steps of the calvin cycle require light directly 3. Examine figure 7.5B and describe it aloud. Try to then look away and replicate similar drawing here in pencil. Correct it until you have all the inputs and outputs of both parts. -Inside the chloroplasts both light reactions and the calvin cycle occur. While both are occurring, they recycle the following: Light reactions end up with ATP and NADPH which it gives to the calvin cycle so that the calvin cycle can use that stored energy to power its reaction. The calvin cycle ends up with NADP+ and ADP+P which it gives to the light reaction so that the light reaction can use those to transfer electrons.

4. What kind of visible light do plants NOT absorb well? Why do plants have various pigments in the chloroplast? Plants do NOT absorb green light well. Instead, they reflect it, which is why it is green colored. -Plants have various pigments because different pigments can only absorb certain kinds of light. -Cartenoids are a type of pigment which are various shades of yellow and orange  they are most importantly used for photoprotection (some cartenoids absorb and dissipate excessive light energy that would otherwise damage chlorophyll) 5. Describe what light does in a photosystem by writing a detailed legend for fig 7.7B. In the thylakoid membrane, photosystems are clusters of chlorophyll molecules that contain both a reaction-center complex and many various pigment molecules. The light harvesting complexes are like light gathering antenna and then it is passed like a human wave into the reaction center complex. The reaction center complex has a pair of special chlorophyll a molecules as well as a primary electron acceptor (accepts electrons and becomes reduced). When an electron from a reaction center chlorophyl a is boosted to a higher energy level, it is immediately captured by the primary electron acceptor.

6. Before looking at the details of electron transport and chemiosmosis of module 7.9, describe Figure 7.8—a mechanical analogy. What is the big picture relative to electrons? Figure 7.8 – a protein (aka H+ ion) catalyzes the system by reducing photosystem II (giving it electrons) then the electrons go down the electron transport chain where another proton (H+ ion) causes it to go to photosystem I which then transfers it finally to NADP+ to create NADPH

Electrons flow from _water__ ultimately to _NADP+___, which is reduced to _NADPH______. 7. Just like in aerobic respiration the electrons lose small amounts of energy as they “bounce” from one electron carrier to the next. That released energy is used to do what cellular work? Their released energy is used to pump H+ ions across a membrane. They pump them against their concentration gradient, which creates a high potential energy in the thylakoid space (?) that can then be used to power ATP synthase to make ATP 8. Similar to mitochondria during aerobic respiration, a H+ gradient is generated across membranes (meaning there are more H+ on one side than the other). In the chloroplast, in what compartment do more H+ build up in? _thylakoid space _____. These H+ then flow through what protein? _ATP synthase___ as they follow their concentration gradient (from high to low). What product of the light reaction has just been made as a result of the H+ gradient? ATP!

9. Electrons in photosystem II would eventually be used up if not replaced. Water plays a role in replacing electrons. How? What part of the water molecule is used in the process and what part diffuses away? Water is split in the thylakoid space, and its electrons are passed to photosystem II. The leftover oxygen atom combines with another to form O2, which is released through the plant (where we get our O2) 10. Look at your overview fig 7.5B again. Have you learned all the inputs and outputs of the light dependent reaction yet? Be sure to review. Let’s consider the last output: NADPH. After electrons bounce through the electron transfer chain following photosystem II, they have lost considerable energy. They get re-excited at photosystem I and get passed to another electron transfer chain. What is the terminal electron acceptor in this reaction? _ NADP+_____ What is it called once it is reduced? _NADPH _____. Is it useful to the cell? Why? Yes, it is necessary to power the Calvin cycle, which goes hand in hand with the light reactions -Inputs of light reaction: -H20 -sunlight -NADP+ -ADP + P -Outputs of light reaction: -NADPH -O2 -ATP -NADPH 11. The Calvin cycle takes place where in the chloroplast? _the stroma (the fluid around the thylakoids) ___What is the chemical formula for glucose? __C6H12O6__ So, how many carbons are in the molecule? _ 6_____ Therefore, how many carbon dioxide molecules will be needed from the atmosphere? __6__ 12. Taking carbon from the carbon dioxide in the air (called an inorganic molecule) and attaching the carbon to an organic molecule is called __ carbon fixation___. In the chloroplast, the name of the enzyme that performs this process is called _rubisco____________

For the purpose of intro biology, we want to take away the major points of the Calvin cycle: How many ATP total are needed to make one glucose? _9_______ How many NADPH are needed to convert total to make one glucose? _6_______ How can the chloroplast get more ATP and NADPH? Photosynthesis ? Readings: Section 37.19 and 38.4 13. Look at your finger nail. Think about the protein keratin that makes it up. Keratin is an organic molecule consisting of many carbon atoms. Where did those carbon atoms originally come from? Those carbon atoms originally came from photosynthesis and then were in a primary consumer I ate or a plant I ate. 14. How does photosynthesis remove carbon dioxide from the air? Photosynthesis incorporates CO2 into organic molecules during the Calvin cycle when CO2 binds to RuBP sugar which help from enzyme Rubisco (carbon fixation)

What happens to carbon in the wood of a tree when it is burned? It is released into the atmosphere and is dangerous because too much carbon dioxide in the atmosphere is leading to global warming List things that increase CO2 in the atmosphere.

List things that remove CO2 from the atmosphere.

-burning wood and fossil fuels -photosynthesis (plants) -cellular respiration from animals/decomposers -surface water of ocean -surface water of ocean 15. What is the global consequence for the atmosphere if CO2 output by respiration exceeds its intake by photosynthesis and absorption into the ocean? When we have too much CO2 in the atmosphere and not enough plants to perform photosynthesis and remove CO2, global warming increases 16. What happens to the oceans as they absorb more and more CO2? It affects the ocean’s chemistry. When CO2 dissolves in water, it becomes carbonic acid. The ocean has become increasingly more acidic and this can especially effect organisms with exoskeletons sine they are made of calcium carbonate.

sunlight Light reactions

oxidized

Electron transport chain

Calvin cycle

reduced

NADPH...