Biology 1441 1st Edition Exam 2 Study Guide Chapters 7 10 Chapter 10 Photosynthesis Photosynthesis converting solar energy into chemical energy nourishes the whole world Autotroph sustain themselves without eating anything derived from other living creatures producers Heterotrophs obtain their organic material from food consumers Chlorophyll green pigment located within the chloroplasts gives plants their green color Mesophyll interior tissue of leaf where chloroplasts are located Stomata microscopic pores of the leaf where oxygen enters and carbon dioxide leaves the leaf Stroma dense fluid within the chloroplast enclosed by an envelope of 2 membranes Thylakoid interconnected membrane sacs that separate stroma from other compartments location of chlorophyll Redox Reactions in Photosynthesis Chloroplasts split into hydrogen and oxygen Incorporates electrons of hydrogen into sugar molecules Hydrogen is oxidized and CO2 is reduced oxygen is released as a molecular oxygen In photosynthesis electrons increase in potential energy as they move from water to sugar This requires energy sunlight 2 stages of photosynthesis light reaction and Calvin cycle 1 Light reaction converting solar energy into chemical energy a Water is split releasing oxygen as a by product light absorption forms NADP b Photophosphorylation light reactions generating ATP using chemiosmosis to power the addition of a phosphate group to ADP c NAD reduced into NADPH by adding electrons and a H d No sugar is produced 2 Calvin Cycle a Carbon fixation incorporating carbon into inorganic compounds This reduces carbon into carbohydrate by adding electrons with power provided by NADPH acquired from light reactions b Makes sugars with NADPH and ATP produced in light reaction c It is a dark reaction doesn t need sunlight directly d Occurs in stroma Wavelength distance between crests of electromagnetic waves Electromagnetic spectrum entire wavelength of radiation 380 to 750 is most important to life Visible light radiation that can be detected as various colors by the human eye Photons discrete particles that act like objects because they have a fixed amount of energy What is the relationship between wavelength and energy in a photon The shorter the wavelength the greater energy each photon possesses this is an inverse relationship Spectrophometer measures a pigment s ability to absorb many wavelengths of light Absorption spectrum plots a pigment s light absorption versus wavelength Chlorophyll A participates directly in photosynthesis light reactions absorbs blue green colors Reflection bouncing back this is the color we see Transmission light passing through ex A microscope Absorption light used as energy Black objects reflect 0 light and gain heat faster than white objects which reflect all light Refraction bending light Chlorophyll B absorbs olive green colors Carotenoids yellow and orange absorbs violet and blue and green light They broaden the spectrum of colors that can drive photosynthesis Excitation of Chlorophyll II by Light Absorption of a photon boosts an electron to an orbital of higher energy Photons absorbed are those whose energy us exactly equal to the energy difference between the ground and excited states A particular compound absorbs only photons corresponding to specific wavelengths which are unique to each absorption spectrum Photosystem composed of a protein called a protein core complex Reaction center complex 2 chlorophyll A molecules Light harvesting complex pigment molecules bound to proteins Light Harvesting Complex Various pigments that allow a photosystem to absorb a wider range of wavelengths Pigments absorb photons transfer that energy photons from a pigment molecule to pigment molecule then to chlorophyll A molecules in the reaction center Reaction Center Chlorophyll A special molecule environment enabling them to use energy from light to boost electrons to a higher level and transfer them Primary electron acceptor accepts excited electrons from chlorophyll A Light Reactions Step 1 solar powered transfer of an electron from chlorophyll A to primary electron acceptor As soon as chlorophyll electrons excite to a higher energy level primary electron acceptor captures it This is a redox reaction 2 photosystems in light reactions photosystem II P680 and photosystem I P700 Both photosystems use light to generate ATP and NADPH Linear electron flow flow of electrons through the photosystems and other molecular components built in thylakoid membrane occurs in light reactions of photosynthesis What is the strongest oxidizing agent P680 1 Photon of light excites an electron transferring a photon from 1 pigment to another Passes to a P680 chlorophyll A molecule in photosystem II 2 Excited P680 is oxidized into P680 3 Enzyme catalyzes splitting of H20 into 2H and 1oxygen Electrons are supplied one by one to P680 pair Oxygen forms 02 4 Each electron passes from primary electron acceptor to PSII to PSI vis electron transport chain made up of plastoquinane Pq and plastocyanin 5 Exergonic flow of electrons to lower energy provides energy for ATP synthesis Hydrogen ions pass through cytochrome 6 P700 is excited to P700 accepts electrons fro bottom of electron transport chain P700 is the final electron acceptor in 1st electron transport chain 7 Photo excited electrons passed in a series of redox reactions from primary electron acceptor through ferredoxins Fd in 2nd electron transport chain No proton gradient or ATP produced 8 NADP catalyzes transfer of electrons from FD to NADP forming NADPH 2 electrons transferred Cyclic energy flow flow of photo excited electrons which uses photosystem I but not photosystem II Fd P700 No NADPH production no oxygen released but still generates ATP Chemiosmosis in Chloroplasts and Mitochondria Both generate ATP by chemiosmosis but have varying energy sources Mitochondria transfers chemical energy from food to ATP Chloroplasts transform light energy into chemical energy ATP Electron transport chain transforms redox energy to a proton motive force Redox energy drops in free energy from electron transfer The proton motive force establishes a gradient ATP Synthase in membrane phosphorylates ADP Oxidative phosphorylation high energy electrons dropped down electron transport chain are extracted from organic molecules food Photophosphorylation water is the source of electrons light energy drives electrons from water to ETC spatial organization of chemiosmosis differs in the chloroplast