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Cell Membrane
Medical Cell Biology
| Term | Definition |
|---|---|
| Components/character of a cell membrane | Phospholipid bilayer, cholesterol, proteins. Asymmetric |
| Membrane lipids | Phosphotidylcholine, phosphotidylserine, phosphotidylethanolamine, phosphotidylinositol, and sphingomyelin |
| Membrane lipids found in the outer leaflet | Phosphotidylcholine and sphingomyelin |
| Membrane lipids found in the inner leaflet | phosphotidylserine, phosphotidylethanolamine, and phosphotidylinositol |
| Which membrane lipid should never be in the outer leafleat | Phosphotidylserien. Unless it is for RBC 120 days break down or for platelet aggregation |
| Glycolipids | Made in the Golgi, carbohydrate that is EXCLUSIVELY attached on the outter leaflet, blood group antigen recognition |
| Cholesterol | Help maintain structural integrity of plasma membrane at extrem temperature. Less cholesterol = more fluidity. More cholesterol = more rigid. |
| Lipid Turnover | Remodelling or repairing damage from endocytosis, exocytosis, oxidative damage, ROS attacking polyunsaturated fatty acids. |
| Phospholipase A2 (PLA2) | Hydrolyzes phospholipids into lysophospholipid (LPL). FA + Coenzyme A = FattyCoA. LPL + FattyCoA = New Phospholipid |
| PLA2 in arachidonic acid hydrolysis | PLA2 hydrolysis phospholipids --> arachidonic acid. 1) Arachidonic acid --> 5-lipoxygenase --> Leukotrienes 2) Arachidonic acid --> cycloxygenase --> PGH2 --> Prostaglandins and thromboxanes |
| What inhibits the COX enzyme? | aspirin |
| Phospholipase C | PLC generates DAG for signal transduction. GPCR can activate PLC which then leads to the production of DAG and IP3 |
| Flippase | ATP dependent. Outer to inner (unity directional) |
| Scramblase | ATP independent. Ca+2 activated. Always flip things from inside to outside. Brings PS on the outer surface |
| What is the consequence of a non functioning Ca+2 ATpase | Cannot pump out excess Ca. Influx of Ca inside cell will stimulate scramblase. Scramblase will bring PS on the outer leaflet |
| Active scramblase + Flippase | minimal PS exposure |
| Active scramblase + deactivated flippase | Exposure of PS on outer surface In case of sickle cell anemia, PS should not be on the outer leaflet. This causes cells to stick together |
| Lipid Raft | Region of cell membrane where lipids and proteins enriched. Decreased membrane cholesterol leads to melting of lipid raft |
| Lipids | Cholesterol, sphingolipids, sphingomyelin and glycolipids |
| Integral Membrane Proteins | Integral membrane proteins don't flip flop. They can either be single pass or multipass |
| Single pass integral membrane protein | Membrane spanning region: hydrophobic. Regions in cytosol and outside cell: hydrophilic. Example glycophorin A |
| Multi-pass integral membrane proteins | Includes transporters, ion channels. Membrane spanning regions may include polar or charged amino acids. Example Band 3 |
| Peripheral Membrane Protein | Associated through ionic interaction with an integral or another peripheral membrane protein |
| Diffusion | Small, hydrophobic or hydrophilic molecules can diffuse through membrane according to their concentration gradient (N2, O2, EtOH, Urea) |
| Osmosis | Water movement (hyperosmotic, hypoosmotic, iso-osmotic) |
| Aquaporins | Used for transport of water, leading cause of cataract in children, Integral membrane proteins, Defects can lead to nephrogenic diabetes insipidus, congenital cataracts in children |
| Donnan Effect | The presence of large molecules on one side balances the greater concentration of a certain ion on the other side. Na+ moves in, water follows, cell burst. |
| How is the Donnan Effect balanced? | Na+/K+ATpase by pumping out 3 Na+ ions and take 2K+ |
| Facilitated Transport | Facilitated transport is required when molecules are too large. |
| GLUT | Facilitated transporter. Used for glucose transport.Pri |
| 2 types of Active Transport | Primary and Secondary Active transport |
| Primary active transport | Movement of molecules across a membrane against its concentration gradient. Need ATP |
| Secondary active transport | Movement of molecule 1 across a membrane using free energy derived from transport of molecules 2 down the electrochemical gradient; co-transport |
| Primary Active Transport | Na/K ATPase. Transport 3 Na+ ions out of cell and 2 K+ ions into cell uses 1 ATP. |
| Ouabain and digitalis | inhibits Na/K ATPase pump. Increases [Na+] and [Ca2+]. Increases contractile activity |
| Symport | Same direction. Example Na/Glucose (or amino acid) symport (SGLT) |
| Antiport | Opposite direction. Example: Na/Ca |
| CFTR defect | Accumulation of Cl- ions outside of cell. Sweat test will show elevated level of Cl- |
Created by:
jsabangan
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