<p>Does anyone know how to explain P700 and P680 in the noncyclic electron flow? Does NADP gain two electrons and becomes reduced to NADPH? </p>
<p>Also, what is the enzyme that attaches RuBp to carbon dioxide during the Calvin cycle in C4 plants? How is the mesophyll structure different from C3 plants? Is there really no difference? </p>
<p>AND…how have prokaryotic organisms evolved from eukaryotic organisms? I suspect it has something to do with organelles being consumed over time</p>
<p>. . bump . .</p>
<p>Just skimmed through my book and found this:</p>
<p>“Phase 1: Carbon fixation. The Calvin cycle incorporates each CO2 molecule by attaching it to a five-carbon sugar named ribulose biphosphate (abbreviated RuBP). The enzyme that catalyzes this first step is RuBP carboxlyase, or rubisco.”</p>
<p>Water is split at Photosystem II (P680) into hydrogen and oxygen. The electrons are sent (one at a time) to Photosystem II (P680). Here sunlight excites these electrons to a high energy state, and they are captured by an electron acceptor, before slowly losing energy and entering Photosystem I (P700). The electron is again excited by sunlight and captured by an electron acceptor. After it loses energy, it is captured by NADP+. Once NADP+ captures 2 electrons, it becomes reduced and is now known as NADPH (its full name is NADPH+H, after all, it has TWO electrons, one from each hydrogen). NADPH later comes into play in the Calvin cycle, where it transfers these electrons to the carbon compound to reduce it.</p>
<p>In C4, the enzyme that first fixes carbon is PEP Carboxylase (NOT Rubisco as in C3 plants). The difference between C4 plants and C3 plants is that in C4 plants, carbon is fixed by PEP Carboxylase into Malate first in the Mesophyll cells (the “Hatch-Slack Pathway”) and then it goes through the Calvin Cycle in the Bundle Sheath cells. In C3 plants it all takes place in the Mesophyll, not the bundle sheath. Thus, in C3 plants the mesophyll layer is much thicker, but in C4 plants the bundle sheath cell layer is thicker.</p>
<p>Also, eukaryotes evolved from prokaryotes, not the other way around. This is called the theory of endosymbiosis (“endosymbiont theory”). A long time ago, early eukaryotes may have endocytosed (engulfed) prokaryotes, but did not digest them. Eventually they formed a symbiotic relationship. This is why organelles like mitochondria and chloroplasts have a double membrane (or even triple in some cases), and their own DNA in the form of a plasmid (circular DNA, just like prokaryotes such as bacteria). Also, mitochondria have their own ribosomes, that are the same size as bacterial/prokaryotic ribosomes.</p>
<p>Campbell is a good book, it has everything you need to know. Just read the entire chapter(s) and you should get all this stuff.</p>
<p>Does anyone know what’s the difference between Campbell 7th edition and 6th edition? (I use the 6th edition)</p>