Zoology101: Animal BiologyLast Lecture Outline Lecture 8 1. Archaea2. Eukaryotic Cells• Animal Cell3. Nuclear Components• Nucleous• Lamina4. Protein sorting/targeting 5. Intro to Endomembrane SystemCurrent Lecture 1. What Happens in the ER• Process of protein 2. What happens in the Golgi?3. Lysosomes4. Cytoskeleton 5. Peroxisomes 6. Mitochondria and chloroplast7. Evolution of Eukaryotic Cell What Happens in the ER• Steps of a protein◦ Secreted proteins enter ER as they are being synthesized by ribosome◦ Protein exists ER in a vesicle ('Bleb')◦ Protein travels through cisternae of Golgi ◦ Protein enters a secretory vesicle that fuses with cell membrane ◦ Protein is secreted from cell• Protein folding: with help of chaperones (proteins that help other proteins fold)• Chemical modification: glycosylation◦ attachment of oligosaccharide (made in rough ER) → glycoprotein• Cleavage: cutting of proteins What happens in the Golgi?• Further modification of proteins and lipids made by ER• Glycosylation, trimming • Sorting station before molecules move to final destinations• Carbohydrate synthesis• Final destinations: Secreted outside the cell (exocytosis), plasma membrane, lysosomeLysosome• Digestive compartment: recycle center of cell• contains hydrolytic enzymes • pH=5; in order to breakdown molecules, more acidic than cystol ◦ How? Proton pump in lysosomal membrane increase H+ concentration◦ Why? Optimal pH for hydrolytic enzymes ◦ Products get transported after digestion◦ lysosomes can fuse with endocytic vesicle (phagocystosis) ◦ Lysosomes can digest materials in cell (autophagy) • Lysosomal storage diseases◦ Pompe's disease. ▪ Defect in enzyme• gylcogen build up in muscle/liver cells → organs destroyed • Proteins localized in ER by cellular zipcode= signal peptide • Soluble protein with signal peptide and no other zipcode-> excreted from cell• Membrane protein with signal peptide and no other zip code → plasma membrane• Proteins that need to stay in ER have signal peptide and another zipcode: ER retention signal • Lysosomal proteins have signal peptide and zip code • What if it doesn't make it to ER?◦ Dentine Dysplesia Type 2: abnormal dentine of primary teeth • Makes it, but doesn't fold properly?◦ Pumps chloride ions across membrane, water flows the Cl- across the membrane when working properly◦ Cystic fibrosisCytoskeleton• Microfilament: subunits called actin (protein) strands and twist, cell division help pinch◦ dynamic: builds and can tear down based on needs of cell• Microtubule: little tubes in cell- protein subunits → tubuline; chromosome movement and vesicle transport◦ 2 proteins in tertiary form to make a quaternary structure and build up◦ Dynamic• Intermediate filament: NOT DYNAMIC , nuclear lamin• All types of cytoskeletal elements involved in structural support of cell• Vesicle transport: microtubules in combination with motor proteins◦ converts energy of ATP into motion◦ highway between endoplasmic reticulum and golgiPeroxisomes • Oxidation: breakdown of molecules • Not part of endomembrane system• cellular macromolecules: fatty acids, toxin breakdown• Breakdown products into products and hydrogen peroxide◦ Hydrogen peroxide is dangerous to the cell; peroxisomal enzyme (catalase) divides hydrogen peroxide into water and oxygenMitochondria and Chloroplast• Not in endomembrane system• Energy conversion• Mitochondria: ◦ sites of cellular respiration◦ food energy → ATP◦ found in all eukaryotes • Chloroplast◦ sites of photosynthesis in plants ◦ solar energy → chemical energy◦ found in plants and some protists ▪ Both: double membrane, DNA is small and circular, Ribosome (prokaryotic), size- typical bacterial cellEvolution of Eukaryotic Cell• How did compartmental organization arise from prokaryotic cells?◦ Specialized folding of prokaryotic plasma membrane → nuclear envelope, golgi, ER◦ Endosymbosis → mitochondria• Support smooth ER◦ endosymbiotic relationship exists in the modern world◦ similarity between bacteria, chloroplast and mitochondria◦ Divide by binary fission◦ single circular chromosome ▪ “prokaryotic
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