BMB 251 1st Edition Lecture 37 Outline of Last Lecture I. Clicker QuestionsII. Glycosylationa. Glycoproteinsb. GlycolipidsIII. Endoplasmic ReticulumIV. Types of Vesiclesa. Coatedb. Transportc. ClathrinV. Rab proteinsVI. SNARE proteinsOutline of Current Lecture VII. Golgia. Cis faceb. Trans faceVIII. Lysosomes IX. MitochondriaX. ChloroplastXI. Cellular Respirationa. Glycolysisb. Citric acid cyclec. Electron transport chainCurrent Lecture- What is the difference between vesicle tethering and vesicle docking?o A docked vesicle has v-SNAREs and a tethered vesicle has t-SNAREs- Golgi: collection of flattened, membrane-enclosed compartments (“cisternae”), which resembledstacked pancakeso Localization near nucleus depends on microtubules being polymerized o Cis face: entry face  Cis Golgi networks (CGN): fused vesicular tubular clusters from ERo Trans face: exit face  trans Golgi network (TGN): proteins and lipids exit hereo Oligosaccharide processing step occurring in Golgi (glycosylation)o **ER  CGN: sorting (phosphorylation of oligosaccharides on lysosomal proteins)  cistcisternae  medial cisternae  trans cisternae  TGN (sorting)  lysosome, secretion,plasma membraneThese 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.o Golgi, unlike ER, contains many sugar nucleotides, which glycosyl-transferase enzymes use to perform glycosylation on proteins and lipidso Mannose on N-linked oligosaccharides in ER are removed, other sugars are then added- Lysosomes: membrane-bound compartments filled with soluble hydrolytic enzymes that control intracellular digestion of macromoleculeso Include proteases, nucleases, glycosidase, lipases, phospholipases, etc. o **All are acid hydrolases which operate best at pH = 5, slightly lower than normal pH o ATP-driven H+ pump in lysosomal membrane maintains low pH o Newly synthesized lysosomal proteins transported to the lumen of ER and then through the Golgi to late endosomes via clathrin-coated transport vesicleso Lysosomal hydrolases contain N-linked oligosaccharides  covalently modified ubiquitin in CGN so that mannose residues are phosphorylated- Mitochondria and chloroplasts contain their own, smaller, circularized DNAo Mitochondria started as anaerobic cyanobacteria, and were engulfed by a eukaryotic celloriginally lacking early mitochondria. o Chloroplast was another prokaryote that was also engulfed by a larger organism and lived in symbiosis, after mitochondria was already presento Many of the genes that are present in mitochondria and chloroplasts are also present in the eukaryotic nuclear DNA as well-there are only a small percentage that are actually unique to the organelleso There is a slight variation of the genetic code in mitochondria; DNA only comes from thematernal genes - Cellular respiration: glucose (food) is oxidized through glycolysis within the cytosol into pyruvate,which is further oxidized within the mitochondrial matrix (via citric acid cycle and the electron transport chain), until they are finally used in oxidative phosphorylation of ATP - The reduction of carbon is unfavorable, and so the sugars from glucose are taken away and used to make a gradient- NADP+ is very good at accepting electron pairs to make NADPH and then giving them up again where energy is needed- Glycolysis: the first step of cellular respiration occurs in the cytoplasm; original food molecule (glucose) is turned into pyruvate (pyruvic acid)o 2 ATP molecules are put into the system to break the original molecule of glucose into fructose1, 6-biphosphate o The 6-carbon molecule is cleaved into two, 3-carbon sugars of pyruvateo Glycolysis produces a net gain of 2 pyruvate, 2 NADH’s (reduced form of NAD+) and 2 ATP molecules (actually creates 4 molecules, but two were used to initially start the reaction)o The pyruvate molecules contain most of the energy from the original glucose molecule, and then moves across the mitochondrial membrane on to the citric acid cycle - Citric acid cycle: occurs within the mitochondrial matrix o Pyruvate molecules are converted into acetyl CoA, and then go through further oxidationo Electrons are removed from acetyl CoA, which reduce more NAD+, along with the other electron carrier FAD+ o This is where glucose metabolism endso The products of this reaction are 3 molecules of NADH, a molecule of FADH2 and one GTP molecule (no ATP actually created here) per pyruvate moleculeo All of the energy is stored in the NADH and FADH2 molecules, which move on to the electron transport chain- Electron Transport Chain (ETC)o The high energy electrons from NADH and FADH2 are then passed to a set of membrane-bound enzymes in the ETCo The high-energy electrons are passed down the chain, and each further protein along has a higher electronegativity, and therefore a higher affinity for the electron than the last protein had. As the electrons move down the chain, they lose energy, which is then given off to drive the proton pump (moves H+ ions across the membrane)o The electron reaches oxygen, which acts as the final electron acceptor, and the maximum amount of free energy is released, which allows more protons to be transported across and a greater increase in the voltage charge building up across the membraneo This charge differential (voltage) from the H+ ions moving across the membrane is then used to drive ATP synthase in phosphorylating ATP oxidatively o A total of (ideally) 38 ATP molecules can be produced per molecule of glucose, most of them via the ETC and oxidative phosphorylation (this many is never actually made though, because a lot of the energy is given off during the process)- Both cellular respiration and photosynthesis use “chemiosmatic coupling”o They both take energy in order to oxidize the carbons in glucose or the photons, respectivelyo They transfer this energy into electrons, which then drive a proton pump in order to create a voltage gradient across the membrane o They both couple this flow down the gradient to produce ATP as a final product- Photosynthesis: use energy (electrons) from water molecules to start the