Membrane Traffic 1 and 2
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- Created by: amazingemilyjones
- Created on: 15-04-19 16:23
Membrane Traffic 1 and 2
Membrane Traffic 1 and 2
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Proteins
- Proteins on the membrane - not just plasma membrane
- A lot of receptors/channels are drug targets
Plasma Membrane
Lipids in Cellular Membranes
Lipid Rafts
Lipids are Asymmetrically Organised
Endocytosis
- Internalisation of very important molecules
- Cell uptake of extracellular nutrients
- Iron - transferrin - transferrin receptor
- Fats - LDL via LDL receptor
- Proteins - for degredation, downregulation of oncogenic signals - cancer
- Cell recovery through endocytic recycling - protens and lipids
- Cholesterol homeostasis
- LDL receptor
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Endocytosis
- 1 - macropinocytosis
- 2 - clathrin coated vesicles
- 3 - clathrin independent endocytosis
- 4 - clavaeolae - platform is lipid raft
- 5 - phagocytosis
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Material is taken into cells in clathrin coated ve
Endocytosis and pH
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Lysosome - The Acidic Cell Stomach
Receptor Mediated Endocytosis
- Transferrin binding to transferrin receptor
- Epidermal growth factor (EGF) binding to EGF receptor
- LDL binding to LDL receptor
- benefits to the cell
- endocytic pathway transversed by receptor and ligand
- All these rely on clathrin mediated endocytosis
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Iron
- Anaemia - too low
- Haemochromatosis - too high
Receptor Mediated Endocytosis of Epidermal Growth
Lipid Transportation in Cells - Hyperlipidaemias
- Fats being hydrophobic need specialised transport
- Lipoprotein complexeds (endogenous fats)
- Products of digestion carried by proteins
- Triglycerides --> beta-globulins
- Cholesterol --> beta-globulins and synthesised in the body
- Phospholipids --> alpha-globulins
- Free fatty acids --> albumins
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Plasma Lipids and Lipid Transport
- Insoluble - need to be transported
- for solubility
- for recognition
- Free fatty acids bound to the plasma protein albumin
- Cholesterol, triglycerides and phospholipids are transported as lipoprotein complexes
- Proteins associated with them are called apoproteins
- Major apoproteins - APO E, APO C, APO B
- Proteins associated with them are called apoproteins
- LDL - very important lipoprotein complex
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Receptor Mediated Endocytosis of LDL Receptor
Phagocytosis and Autophagy
- Phagocytosis - cell eating from the outside
- Immune cells - macrophages, neutrophils, dendritic cells
- Autophagy - eating from the inside
- Old and damaged organelles are wrapped in membrane and derived to lysosomes for degradation
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The Secretory Pathway
- Delivery of membrane proteins
- Transferrin receptor
- CFTR
- LDL receptor
- Soluble proteins via exocytosis
- Insulin (hormone), pepsin
- Small molecules via exocytosis
- Neurotransmitters - acetylcholine and noradrenaline
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Proteins travel from endoplasmic reticulum in vesi
Insulin
The first:
- hormone isolated from animal source in a form that could be administered therapeutically to humans
- hormone to have its mechanism of action elucidated
- hormone to have its primary and secondary structure determined
- hormone to be measured using radioimmunoassay
- hormone discovered to be processed as a larger immature form
- hormone to be synthesised using recombinant DNA technology - bacteria E.coli
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Insulin
Membrane Traffic and Disease
- There are many hundreds of diseases associated with membrane traffic
- Examples:
- Cystic fibrosis - indirect
- Traffic of Cystic Fibrosis Transmembrane Conductance Regulator (CFTR)
- Niemann Pick Type (NP-C) - direct
- Defects in transport of lipids to lysosomes
- A lysosomal storage disease
- Cystic fibrosis - indirect
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