BICH 411 1st Edition Lecture 11Outline of Previous LectureI. Photosynthesis OverviewII. Energy transductionIII. PhotosystemsIV. Z schemeV. Cytochrome b6f complexVI. Quantum YieldOutline of Current Lecture I. Cyclic photophosphorylationII. Carbon dioxide fixationIII. Calvin CycleIV. Light activationV. Hatch-Slack PathwayCurrent Lecture**remember that there is a low proton concentration (higher pH) in the stroma, and high proton concentration (lower pH)in the lumen of the thylakoid where the protons are being pumped.**remember plants have mitochondria in addition to chloroplasts, so can also do respiration**more expensive to make ATP in chloroplasts instead of mitochondria – takes 14 subunits in ATPaseThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.cyclic photophosphorylation – bypass of photosystem II, depends only on photosystem I. The electron goes straight from photosystem I to the PQ pool and the cytochrome b6f complex (plastocyanin also involved)Carbon dioxide fixation – Calvin showed that CO2 was combining with Ribulose-1,5,bisphosphate (RuBP, 5 carbon CO2 acceptor) to form 6 carbon molecule. The 6 carbon molecule splits into 3-P-glycerate molecules*Ribulose-1,5-bisphosphate is a primer!! (like oxaloacetate in the TCA cycle)* **know about this acceptor for the test** This is the substrate, and also inhibits Rubisco. Rubisco has to release it before it can be activated (Rubisco activase causes this).**RuBisCO is the enzyme (carboxylase/oxygenase) – activates when carbon dioxide is added to it, has Mg2+ bound to it. *don’t need to know the Ribulose-1,5-bisphosphate mechanism but know that and ene-diol intermediate is involved! Also know that the split occurs between carbons 2 and 3 to form the two 3-P-glycerates. The Calvin cycle3-P-glycerate glucose **Anabolic reaction**-don’t need to know each reaction step but know the net reaction:6 CO2 + 18 ATP + 12 NADPH + 12 H+ + 12 H2O glucose + 18 ADP + 18 Pi + 12 NADP+Light activation-light activates the Calvin cycle enzymes-the light induces the pH change in the chloroplasts, where the enzymes work better at higher pH (in stroma)-the light energy also gives you more reduced ferrodoxin and NADPH, helps move Mg2+ into stroma (very important for rubisco)*figure 21.26 shows how respiration and photosynthesis work together – light regulates on/off switch for carbon fixation. When off, the citric acid cycle is on.-Ribulose-1,5-bisphosphate (RuBP) helps O2 join with RuBP which leads to less RuBP. This resultsin 3-P-glycerate and phosphoglycerate (the latter changes to glyoxylate)Hatch-slack pathway – carries CO2 (via oxaloacetate and malate) to cells where it won’t interferewith Rubisco. Occurs in some grasses and tropical
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