<p>KEY</p><p>9.4 During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis pp. 172-177</p><p>Directions: as always, answer these reading comprehension questions in your journal. Rephrase the Q's in the A's OR glue this paper in your journal on its own page nearby.</p><p>1. In the electron transport chain (ETC), a) Where do the “starting” electrons come from? From NADH and FADH2, but ultimately… glucose!</p><p> b) What causes electrons to move from one electron carrier to another in the chain? Increased stability as each new carrier gets reduced (accepts e-).</p><p> c) What molecule is the final electron acceptor for the ETC? (It's not considered part of the chain; it "swoops in" at the last moment to whisk away the electrons that have reached the end of the chain.) And what substance forms as a result? Oxygen is the final e- acceptor, and the substance that forms is water.</p><p> d) What substance accumulates between the inner and outer mitochondrial membranes as a result of the moving of electrons along the ETC? Protons, a.k.a. hydrogen ions, a.k.a. H+ ions</p><p>2. Identify the underlined elements of this simile: “The making of ATP in the mitochondria is like the making of a cake; one needs ingredients, energy, and a chef to do the manual labor.” Ingredients: ADPs and phosphates; energy, the H+ gradient; chef, ATP synthase enzyme.</p><p>3. If a eukaryotic cell was unable to get enough oxygen… a) Would its ETC operate? Why or why not? No, e- wouldn't be able to be unloaded at end of the chain. b) Would it be able to make ATP within its mitochondria? No – if ETC doesn't operate, no proton gradient. c) Would the cell be able to have Krebs cycles or perform glycolysis? Why or why not? No Krebs because w/o a running ETC, NADH and FADH2 don't get oxidized. Krebs needs NAD+ and FAD. Glycolysis also needs NAD+, so technically no glycolysis either… but some cells have a trick to enable them to keep running glycolysis in the absence of oxygen. It's called fermentation. Section 9-5 in your text.</p><p>4. Prokaryotic cells have cellular respiration, even though they do not have mitochondria. Where is the ETC of a prokaryotic cell located? Along the plasma membrane. The proton gradient builds up in the prokaryote's cell wall space.</p><p>5. CLEARLY define the five terms below. They are loosely related but you need to understand how they are different! a) chemiosmosis: process in which H+ ions pass through ATP synthase, causing the enzyme to spin; the spinning enzyme synthesizes ATP. b) electron transport: Alternate series of reductions and oxidations as NADH and FADH2 hand off their electrons all the way to – eventually – oxygen, forming water. c) oxidative phosphorylation = ETC + chemiosmosis d) proton motive force = hydrogen ion gradient utilized in chemiosmosis e) substrate level phosphorylation = entirely different way of adding a phosphate group to ADP, forming ATP. Happens at one step in glycolysis or Kreb's. Done by an enzyme. No hydrogen gradient utilized.</p>