Photosynthesis Guided Reading Questions Do these before the Mastering Assignment Reading 7 5 7 10 37 19 and 38 4 Reading objectives Describe the two parts of photosynthesis and the inputs and outputs of both parts Explain what kind of sunlight is used by the plant and why sunlight is necessary Explain photophosphorylation in the light reactions of photosynthesis and describe how photophosphorylation is similar and different from the oxidative phosphorylation in aerobic respiration 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 Inner and outer membranes Granum Thylakoid Thylakoid Space stroma 1 Describe in words what happens in the light reaction of photosynthesis In the thylakoids water is split giving off electrons and O2 Chlorophyll absorbs light energy which drives the transfer of electrons and H from the water to the NADP electron receptor making it NADPH that transfer electrons during cellular respiration So solar energy is converted to chemical energy and stored in ATP and NADPH 2 How is the Calvin cycle linked to the light reaction This is the next stage of photosynthesis that occurs in the chloroplasts and makes sugar using CO2 and products from light reaction 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 H2O Light Reaction NADP ADP ATP NADPH CO2 Calvin Cycle Chloroplast 1 4 What kind of visible light do plants NOT absorb well Why do plants have various pigments in the chloroplast O2 Sugar Green because its reflected They have different pigments to absorb different wavelengths of light 5 Describe what light does in a photosystem by writing a detailed legend for fig 7 7B The photosystem harvests light with its light harvesting receptors then the light bounces from stroma to stroma transferring energy Then it passes the reaction center complex with special chlorophyll molecules and the primary electron acceptor This is the first step of transforming light energy into chemical energy 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 The photon provides energy like a huge mallet to the photosystem II to boost it to a high energy level where it is caught by the primary electron acceptor Like a ramp the electrons loaded on the transport chain to photosystem I On the way down electrons release ATP Another photon then pumps it the a higher energy level where the primary electron acceptor catches it and and throws it in a bucket to produce NADPH This shows how the photosystems and transport chains transform light energy to chemical energy to ATP and NADPH Electrons flow from photosystem II ultimately to Photosystem I 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 It through the thylakoid space and goes against the concentration gradient to drive H back across the membrane through ATP synthase 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 When water is split the O2 diffuses while the H are used in the process of replacing electrons 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 NADPH plays a huge role in transporting electrons 2 11 The Calvin cycle takes place where in the chloroplast The stroma 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 18 How many NADPH are needed to convert total to make one glucose 12 How can the chloroplast get more ATP and NADPH From H2O in thylakoid discs 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 14 How does photosynthesis remove carbon dioxide from the air It absorbs CO2 and incorporates CO2 in the atmosphere it into organic molecules What happens to carbon in the wood of a tree when it is burned A rapid form of decomposition combustion that releases heat and light very quickly This releases carbon atoms in the form of CO2 List things that increase CO2 in the atmosphere Combustion of fossil fuels Transportation Home energy Burning wood fires List things that remove CO2 from the atmosphere More plants CO2 dissolving in water and becoming carbonic acid 15 What is the global consequence for the atmosphere if CO2 output by respiration exceeds its intake by photosynthesis and absorption into the ocean Climate Change 16 What happens to the oceans as they absorb more and more CO2 There have been accelerated decreases in ocean PH that reduces the concentration of carbonate ions that are used by many coral and plankton 3 Light energy Light
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