M2d L20-21 Flashcards
Describe the structure of the chloroplast and explain how this structure relates to its function
Chloroplast is a double membrane structure, inside the inner membrane we have stacks of thylakoids, called grana, the space is called stroma, granum is a singular, granum is interconnected by stroma lamellae.
Photosynthetic pigments are embedded into the thylakoid membrane, making it the site of the light-dependent reactions in photosynthesis. The stacked coil shape of the grana gives the chloroplast a high surface area to volume ratio, aiding the efficiency of photosynthesis.
Explain the importance of photosynthesis for planet Earth
Photosynthesis is the way biology can renew the energy that’s used up in foods, limited food on earth, all food like food nutrient molecules they are replenished from light energy from the sun
Carbohydrates that are synthesized are a source of energy and a source of carbon skeletons for lifeforms organisms to use to make other molecules, most contain carbon, plants store carbohydrates in structures such as fruits. Photosynthesis produces O2 in the atmosphere and removes CO2 from the atmosphere
Describe the Calvin cycle and role of RuBisCO
CO2 from the atmosphere enters the stroma when the enzyme RuBisCO joins it with ribulose 1,5-bisphosphate (RuBP) to form 3-phosphoglycerate (PGA)
PGA is then phosphorylated and reduced to a 3C glyceraldehyde 3-phosphate (GAP) Some of the GAP molecules are converted into starch or sucrose. Some GAP is used to regenerate RuBP, to keep the cycle going.
Product output from the cycle is (GAP) a triose (3C) sugar 9 ATP and 6 NADPH used 5 of 6 GAP
molecules produced are used to regenerate ribulose bisphosphate to keep the cycle going
Explain how ATP & NADPH are generated during the light reactions, & describe how they are used in the Calvin cycle.
it requires light as the energy source, H2O is oxidized to O2, driven by light, results in phosphorylation of ADP to form ATP, and reduction of NADP+ to NADPH
Explain the involvement of plastoquinone, the cytochrome b6f complex, plastocyanin, ferredoxin and ferredoxin-NADP+ reductase in photosynthesis
Photosystem II absorbs photons and oxidizes water into 4 H+, 4 electrons and O2. the 4 e- are transferred to Q,e- –> QH2, which diffuses through the thylakoid membrane to its binding site on cytochrome b6f, it accepts the e- for transfer to the soluble protein plastocyanin. As this occurs, cytochrome b6f pumps H+ across the the thylakoid membrane, stroma –> thylakoid lumen (2H+/e-) it also moves 8H+ from the stroma to the thylakoid lumen. e- transfer to FNR reduces NADP+ & decreases [H+] in stroma.
Outline/explain the roles of PS II and PS I in photosynthesis i.e. explain the Z-scheme
Electron transfer goes from left to right. Electrons are raised to an excited state by PS II & PS I light energy capture enabling spontaneous electron transfer between partners of the electron transport chain from lower redox potential (higher energy) to higher redox potential (lower energy)
Explain the role of antenna chlorophyll and reaction centre chlorophyll in the capture of light energy (photons)
they receive a proton and go into a higher energy state, transfer that to the next molecule, and keep going until they reach the reaction center, which transfers e- with an electron acceptor
Write the chemical equation for the photosynthetic reduction of NADP+
2H2O + 2NADP+ –> O2 + 2NADPH + 2H+
Describe the organization and function of the chloroplast electron transport chain in the thylakoid membrane
Electrochemical H+ gradient across the thylakoid membrane drives chloroplast ATP synthase. At saturating light intensity, the chloroplast electron transport chain generates a H+ gradient of ~3.5 pH units, 3000 fold difference [H+], (12 H+ per O2) across the thylakoid membrane
where is chlorophyl embedded?
it is embedded into a protein complex in the thylakoid membrane
talk about the electron transport chain from ATP synthase
The chloroplast ATP synthase will utilize the proton gradient from high concentration in the thylakoid lumen to low concentration in the stroma, works similarly to ETC. the CF1 drives the phosphorylation of ATP: ADP + Pi
Net result is synthesis of NADPH & generation of H+ gradient for ATP synthesis
