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Week 8
Photosynthesis
| Question | Answer |
|---|---|
| Photosynthesis definition | Biological process where organisms (plants, algae, certain bacteria/protists) use the energy of the sun to convert light energy into energy (glucose) |
| Chlorophyll function | green pigment where leaves get their color from; absorbs light during photosynthesis (primarily red + blue) |
| Photoautotroph meaning | organisms that create their own organic food through photosynthesis (making organic molecules from H2O + CO2) |
| Describe choloplast | double membrane organelles - site of conversion of light to chemical energy in eukaryotes. contain thylakoids (discs where light reac. occurs) stroma (thick fluid where calvin cycle occurs) found in mesophyll tissue |
| General chemical equation of photosynthesis + what type of reaction is it? | 6 H2O + 12 H2O + light energy -> 6 C6H12O6 + 6 H2O |
| Which molecules get reduced + what gets oxidized in photosynthesis? | H2O is oxidized to form O2 + CO2 is reduced to form carbohydrates |
| 2 stages of photosynthesis + where they take place: | The light reactions (occurs in the thylakoids) + the calvin cycle (occurs in the stroma) |
| Light properties | consists of electromagnetic waves (blue-violet has most energy) + discrete particles called photons |
| How does wavelength relate to light | wavelength determines the color of visible light. shorter wavelengths = violet/blue, longer = red |
| What are pigments | substances that absorb light (wavelengths not absorbed are reflected or transmitted + different pigments absorb differernt wavelengths) |
| Why are leaves green? | chlorophyll reflects are transmitts green light (green light is least absorbed) |
| Absorption spectrum | graph plotting a pigments light absorption vs. wavelength. (violet-blue + red light works best for photosynthesis) (for both graphs, more light absorption = more photosynthesis) |
| Action spectrum | graph plotting the rate of photosynthesis vs. wavelength |
| Accessory pigment meaning + examples | allow photosynthetic pigments to absorb a broader range of visible light + protects the photosynthetic electron transport chain from damage (photoprotection) ; ex. chlorophyll b, carotenes, xanthophylls |
| Photosynthetic pigment meaning + example | initiates light reactions by transferring electrons to the primary electron acceptor; ex. chlorophyll a |
| What happens to excited electrons in a plant cell (4 things) (when pigment absorbs light, it goes from ground stae to an excited/unstable state) | emitted in the form of light via fluorescence, given off as heat alone; excites an electron in a nearby pigment inducing resonance; jumps to another molecule (accepted by an e- acceptor) |
| What is the light reaction part of photosynthesis? | harvest sunlight energy and convert it to chemical energy as ATP + NADPH (done by thylakoids in chloroplasts); increases the potential energy of e- by moving them from H2O to NADPH |
| Resonance meaning | transfer of energy (ex. from 1 pigment molecule from another) without transferring the e- itself. very efficient |
| Photosystem definition | ~200-300 chlorophyll/accessory pigment/organic molecules + proteins organize themselves into the complex (photosystem) embedded in the thylakoid membrane; consists of a reaction center complex surrounded by several light harvesting complexes |
| Photosystem location + components | thylakoid membrane; photon strikes pig. molecule in LHC passed via resonance until it reaches chloro. a molecules in RCC. e- molecules excite + are transfered to PE-E/boost 1 e- to higher energy level. first step in light reaction |
| What happens when when a photosystem absorbs a photon of light? | cholorphyll a molecules get excited initiating light dependent reaction, boosting e- to higher e level (to e- acceptor pheophytin) then to ETC |
| photosystem 1 vs. 2 | (2 happens before 1) PS2/P680 splits water to release electrons/protons/O2 + PS1/P700 uses e- to produce NADPH |
| Photosystem 2 events | P680 (reaction center) gets excited, e- transfer to PE-E =P680+. breakdown of H2O ->2H/2e-/O, e- reduce it to P680; H+ into thylakoid space(contibute to proton gradient), O combine to O2; excited e move to PS1 via ETC |
| Photosystem 1 events | light energy from photon transer for P700 via resonance; excites e-; transfer to e- aceptor (ferredoxin); go down ETC but does NOT produce ATP; NADP+ is reduced to NADPH (2 e- required for its reduction and H+ atom removed contributes to H+ gradient) |
| What is the function of water in photosynthesis | provides e- to replace e- lost; H+ protons to power gradient and is a source of O2 (releases it) |
| what is energy released when e- flow though the ETC used for? | it is used to pump protons agaisnt their concentration gradient from stroma into thylakoid lumen; the energy from the gradient is then used to power ATP synthesis (converting ADP to ATP) that ATP + NADPH then goes into Calvin cycle |
| final acceptor in the linear electron flow | NADP+ / NADPH |
| linear vs. cyclic electron flow? | 2 possible routes for e- flow: linear uses both PS's + produces ATP/NADPH; cyclic uses only PS2 and only produces ATP (cyclic e- flow generates surplus ATP satisfying the higher demand of the calvin cycle) |
| How is proton gradient generated? | H+ from water being split by PS2, cytochrome (between PS1 + 2) transport chain using energy to move H+ accross membrane + removal of one H+ from stroma during reduction of NADP+ |
| Cyclic flow of electrons description + use | e- travel in closed loop in PS1, only purpose is to produce ATP for calvin cycle + to protect photosynthetic machinery from damage (from high energy e- when no NADP+ is returned from calvin cycle) |
| Chemiosmosis in photosynthesis + function of ATP synthease | Chemiosmosis in photosynthesis is used to generate ATP using the H+ gradient from stroma into the thylakoid lumen; downhill movement of e- in ETC releases energy |
| Chemiosmosis in photosynthsis vs. in aerobic cellular respiration (source of e-, final e- acceptor + membrane/compartments where proton gradient is generated) | photosynthesis: water in PS2, NADP+, from stroma -> thylakoid space aerobic CR: breakdown of glucose, O2, from mitochondrial matrix ->intermembrane space |
| Products of light reactions in photosynthesis | O2, ATP + NADPH |
| Calvin cycle definition + location | regenerates its starting materal after molecules enter/leave cycle. builds sugar from sugar molecules by using ATP + the reducing power of e- carried by NADPH. 3 CO2 enters and comes out as GP3 (half a glucose); occurs in stroma of chloroplast |
| 3 phases of Calvin cycle | Fixation, reduction + regeneration |
| Fixation phase | CO2 is added to the 5C sugar ribulose, catalyzed by enzyme rubisco (breaks 6C molcule into 2 3C molecules (3-PGA)); for 1 G3P the cycle must fix 3 molecules of CO2 |
| Reduction phase | energy must be increased by C compounds being reduced; 3-PGA is reduced by: ATP used to phosphorylate it + NADPH transfers 2 high energy e- to the phosphorylated compound) for every 6 G3P produced only 1 can be transferred out of choloplast |
| Regeneration phase | RuBP (ribulose) needs to be regenerated; 3 5C RuBP molecu;es are produced from the 5 remaining G3P molecules (ATP is required) |
| Light reaction summary | generate ATP + increase the potential energy of e- by moving them from H2O to NADPH |
| How many CO2, ATP + NADPH are needed to produce 1 molecule of GP3? | 3 CO2, 9 ATP, + 6 NADPH |
| What is rubisco + fuction? | key enzyme that converts CO2 into 3-GPA |
| Fuction of ATP + NADPH in calvin cycle | ATP supplies energy to converts 3-GPA into GP3 + G3P into RuBP, and NADPH provides e- to convert 3-GPA into GP3 |
| Products of calvin cycle | produces 1 G3P per cycle (half a glucose) (sugar) |
| How do light reactions + calvin cycle depend on eachother? | light reactions provide ATP + NADPH for the calvin cycle, and the calvin cycle returns ADP, Pi, and NADP+ needed for light reactions |
| Why are alternate ways of C fixation needed | |
| Relationship between photorespiration, photosynthesis + arid enviroments | |
| Photo respiration defintion | |
| C4 plant definition | |
| CAM plant definition | |
| finish the alternate C fixation flashcards later |
Created by:
every_august
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