C1.3: Photosynthesis Flashcards

Question

Where does the light dependent reaction take place?

Answer 1

In the thylakoids intermembrane space/across thylakoid membrane Thylakoid membrane contain transfer chain -> electron passed along electron carriers in series of redox reactions

Answer 2

PHOTOLYSIS: The splitting of water molecules using light energy (PSII) CHEMIOSMOSIS: Synthesis of ATP using electrochemical gradients produced by H+ protons -> proton gradient across thylakoid membrane when proton pump from chloroplast matrix -> thylakoid space REDUCTION OF NADP: NADP+ accepts electrons (from photophsphorylaiton) and H+ protons => NDPH (PSI) PRODUCTS: Light energy -> chemical energy in the form of ATP and NADPH (reduced NADP) => transferred to light-independent reaction (in stroma) Oxygen -> waste product

Answer 3

Occurs in PSII - reaction center acts as oxidizing agent -> water molecules split Water -> proton + electrons + oxygen (2H₂O → O₂ + 4H⁺ + 4e⁻) - oxygen waste product -> diffused out via stomata - electron -> electron transport chain - proton picked up by NADP -> NADPH Important because it generates electron for: - replacement of electron in PSII - subsequent reactions

Answer 4

3.5 billion years ago: photosynthetic prokaryotes -> photosynthesize -> oxygen in atmosphere Millions years later: algae and plants evolve to photosynthesize 2.2 billions years ago: oxygen concentration reach 2% (great oxidation event) 600 million years ago: multicellular organisms (mostly photosynthetic) -> oxygen concentration to 20% 300 million years ago: peak oxygen concentration in air 35% -> contributed to large size of organisms at the time Current: oxygen level around 21% -> result of human activities Other changes due to photosynthesis: - minerals in ocean oxidized - oxygen in ocean - distinctive rock formations prodcued - led to banded iron formation -> most important source of iron ore - methane and CO2 levels fell => ice age

Answer 5

PSI only, linear Light absorbed by PSI -> passed to primary pigment (P700) -> electron in primary pigment excited -> emitted from chlorophyll (photoactivation) Electron capture by electron acceptor -> electron transported via electron transport chain -> then back to chlorophyll => provide energy to transport H+ from stroma -> thylakoid via proton pump => build up of protons in thylakoid -> drive synthesis of ATP (chemiosmosis)

Answer 6

Both PSI and II, linear electron pathway Light absorbed by PSII -> passed to primary pigment (P680) -> Excited electrons (PSII)-> electron acceptor -> passed down series of electron carriers (ETC) excited electron slowly release energy, used to generate proton gradient (used to produce ATP) -> excited electron fall and picked up by reaction center (PSI) -> pair of electrons (FROM PSI) and H+ (from water) used to produced NADPH -> electron from photolysis used to replace ones lost from PSII -> electrons from PSII replace ones lost in PSI => main products are ATP and NADPH

Answer 7

The term for the overall process of using light energy and electron transport chain to generate ATP from ADP

Answer 8

CHEMIOSMOSIS: the movement of chemicals (protons) down their concentration gradient -> energy released used by ATP synthase PROTON GRADIENT: Electrons passed through ETC -> release energy -> used to pump protons from stroma to thylakoid -> high concentration of protons build up inside thylakoid (create concentration gradient) -> photolysis also contributed to gradient SYNTHESIS OF ATP: Proton gradient powers ATP synthesis -> protons travel down their concentration gradient (thylakoid to stroma) through ATP synthase (membrane protein) -> energy released by movement of proton -> ADP + Pi = ATP (phosphorylation) => this part is CHEMIOSMOSIS

Answer 9

PSI Chlorophyll in reaction center absorb photon of light energy -> electrons in reaction center photoactivated -> passed to protein outside of thylakoid membrane (ferredoxin) -> ferredoxin reduced -> reduced ferredoxin + H+ from from chemiosmosis + NADP+ -> NADPH NADP+ + 2H⁺ + 2e⁻ → NADPH + H+ - now carry pair of electron -> passed to light-independent reaction

Answer 10

Calvin cycle = light independent reaction In stroma -> within double membrane -> protein rich environment with enzymes needed for Calvin cycle 1. Carbon fixation: Enzyme rubisco catalyze fixation of CO2 2. Reduction: Glycerate-3-phosphate reduced to triose phosphate 3. Regeneration: Ribulose biphosphate regenerated from triose phosphate =>CO2 converted to carbs (glucose) => Calvin cycle relies on products from light dependent

Answer 11

Carbon fixation: the process of CO2 being removed from the external environment and becoming part of the plant/fixed CO2 + ribulose biphosphate ruBP (5C) -> unstable 6C compound -> 2 x glycerate-3-phosphate (GP) Catalyzed by enzyme rubisco -> most abundant enzymes on earth -> works slowly -> need high concentrations -> not effective at low CO2

Answer 12

Triose phosphate (TP) and glycerate-3-phosphate (GP) Hexose sugars = 2 x TP Starch = many hexose sugars (many TP) Lipids/triglycerides = fatty acid (TP -> glycolysis -> link reaction pathway -> acetyl coenzyme A -> conjoined) + glycerol (TP) Proteins = certain amino acids from GP

Answer 13

Calvin used Chlorella algae in this glass vessel (lollipop vessel) -> given sufficient light, CO2, hydrogen carbonate -> all had normal C (C-12) At the start of experiment -> carbon replaced with radioactive carbon (C-14) Sample of algae taken at different internvals -> into hot alcohol to stop photosynthesis Carbon compound separated by chromatography Compounds with C-14 identified by autoradiography -> after 5 seconds showed mostly GP -> GP first product (carbon fixation) -> after 30 seconds range of different compounds

Answer 14

Energy from ATP + hydrogen from NADPH used to reduce GP to triose phosphate (3C)

Answer 15

After reduction: 1/6 of TP -> converted into usable product 5/6 of TP -> used to make RuBP (5C) => 5 TP = 3 RuBP Once regenerated -> continue cycle

Answer 16

Products from light dependent (NADPH and ATP) -> used directly in the Calvin cycle to produce carbs => low light intensity -> products produced slower -> limits GP to TP conversion Once NADPH oxidized in Calvin cycle -> NADP+ return to light dependent to accept electrons at end of ETC => high light intensity -> light dependent more quick -> more NADPH + ATP to drive Calvin cycle => but if NADPH not returned -> light dependent restricted CO2 in the form of HCO3 ions -> accept proton from PSII when water splits during photolysis -> important in ETC CO2 also important in carbon fixation => lack of CO2 prevent both processes

C1.3: Photosynthesis Flashcards

(40 cards)