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| Question | Answer |
| Protein signal sequence | Direct the protein to a particular destination Physical properties (hydrophobicity and charge) decide the direction |
| Nuclear pores | Meshwork of proteins: small water-soluble molecules can pass the nuclear pore Pore complex proteins Nuclear basket Cytosolic fibrils |
| Hur transporteras större molekyler genom membran porerna? | M.h.a. nuclear import receptor (återanvänds) Nuclear localisation signal recognized by nuclear import receptor • Requires energy (GTP) • Proteinerna är veckade |
| Cargo protein | protein som ska transporteras |
| Transport across membranes by protein translocators | tex mitokondrien, kloroplast mm Proteiner är oveckat förutom till peroxisomen - signal sekvensen binder till import receptor protein (a transmembrane protein) - the receptor brings the protein to the protein translocator in the outer membrane and the protein will start go through the outer membrane - It will then find (by lateral difussion) the translocator protein in inner membrane. When their almost parallell the protein will go through the inner membrane Once inside the protein will be folded by chaperon |
| Water-soluble protein delivery to ER | The proteins enter the ER while being synthesized ER signal sequence on protein binds to SRP (signal-recognition particle) in the cytosol. The SRP also binds to the ribosome. => Protein synthesis slows down SRP binds to SRP receptor in the ER membrane and the ribosome is moved to a protein translocator, which causes the release of SRP and the protein synthesis begins again at the same time as the protein goes through the membrane Signal peptidase then cleaves the signal sequence that will be degraded in the bilayer |
| Transport of transmembrane proteins from cytosol to ER | the protein have a hydrophobic start and stop sequence |
| Vesicle budding | Cargo receptor binds to cargo protein adaptin binds to the cargo receptor and starts to form a vesicle. Dynamin cuts of the membrane. Uncoating of the clathrin coat => naked transport vesicle |
| Vesicle docking to deliver cargo | Rab proteins on the vesicle recognizes tethering proteins on the membrane v-SNARE on vesicle binds to t-SNARE on membrane and bring the vesicle closer to the membrane the cargo protein is delivered and membranes fuse togheter |
| Protein modification in ER | • Disulfide bonds → stabilize structure • Glycosylation → protect to degradation, transport signal, glycocalyx |
| Protein quality control before ER exit | • ER retention signal → proteins stays and functions in ER • Chaperone proteins → prevent exit of misfolded proteins |
| Golgi apparatus | Cis to trans - protein modification - protein sorting |
| Exocytosis | = transport from trans-Golgi to plasma membrane |
| Constitutive (unregulated) exocytosis pathway | • supply of new lipids and proteins to plasma membrane: cell expansion, renewing • secretion: further diffusion to other cells |
| Regulated exocytosis pathway | only in specific type of cells: secretory cells • secretory proteins stored in secretory vesicles • extracellular signal needed |
| Endocytic pathways | • the material is enclosed by plasma membrane → intracellular endocytic vesicle → delivery to endosomes 1. Pinocytosis = cellular drinking, by all cells 2. Phagocytosis = cellular eating, by phagocytic cells like macrophages, neutrophils 3. Receptor-mediated endocytosis = specific uptake to avoid large volumes or unnecessary compounds) |
| Tissue | = assembly of cells 4 types of tissue: muscular, nervous, connective, epithelial |
| Epithelia | = sheet of cells covering an external face or lining an internal body cavity a large variation The cells are polarized: APICAL side: at luminal area (= the inner open space or cavity of a tubular organ) BASAL side: at basal lamina BASAL LAMINA: sheet of collagen and laminin – link to other tissue (The basal lamina is a layer of extracellular matrix secreted by the epithelial cells, on which the epithelium sits.) |
| Types of cell junctions | Classification according to their function: 1. Tight junctions: seal - Composed of occludins and claudins 2. Adherens junctions: attachments Linked to cytoskeleton by: - adherens junctions (between epithelial cells) or - desmosome (between epithelial cells) or - hemidesmosome (between epithelial cell and basal lamina) 3. Gap junctions: communications - passive diffusion of inorganic ions and water-soluble molecules (1kDa) - 6 protein subunits called connexon; 2 connexons form a gap junction - Electrical and metabolic coupling between cells (cardiac muscle cells) |
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