biomembrane april 2014(2)
DESCRIPTION
GEWGEWGEWTRANSCRIPT
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BIOMEMBRANE
Rondang R. Soegianto
2014
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MEMBRANE STRUCTURE
- Bilayer
- Fluid
- Asymmetric
- Dynamic
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Peck Ritter P353 Fig 9.22
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Peck Ritter P354 Fig 9.23
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COMPOSITION
- Lipid Phospholipid Sphingolipid Cholesterol
- Protein Extrinsic (Cytoskeleton) Intrinsic (Transmembrane)
- Carbohydrate Oligosaccharide (Sialic acid)
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Harper’s P469 Fig 43-2
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FUNCTION OF COMPONENTS
Phospholipid- Interaction with membrane protein- Effect on protein conformation- Effect on membrane integrity
Sphingolipid- Myelin sheath in nerves
Cholesterol- Contributes to membrane strength- Prevents sticking together of phsphlpd tails - Controls diffusion of water into cells
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Protein
Intrinsic: - Transport - Enzymes - Receptors
Extrinsic: Cytoskeleton
Protein Membrane density Membrane identity
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Carbohydrate
Located on outer surface
Glycoproteins involved in- Cell-cell interaction- Immune system to distinguish self and non-self cells- Blood group substances (individually different but can be matched)
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TRANSPORT
Simple Diffusion- Small molecules: CO2, O2, H2O, Urea Move from high to low concentration
- Facilitated Diffusion by carrier system Transport along concentration gradient Example: Glucose transporter (Glut)
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- Active Transport Involves carrier protein (Transporter) Requires chemical energy (ATP) Moves particles against conc. gradient Ex.: Na+, K+- ATPase, Ca2+-ATPase Proton pump
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Nature of Transport Process
Uniport: Ca-pump
Cotransport Symport: Glucose absorption from intestinal mucosa needs Na+ Antiport: Na-pump, ATP-ADP translocase Anion exchanger (Band 3 in ery- . throcytes)
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Transport of Macromolecules
Endocytosis Receptor-mediated endocytosis Glut 4 carries glucose into muscle and adipose tissue after insulin binding to its receptor
Exocytosis Ex.: In nerve synapse. Vesicles containing neurotransmitter fuse with membranes and secrete vesicle content into synaptic gap.
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CELL COMMUNICATION
Cells communicate physically thru junctions.
Tight junction: Intestinal mucosa
Gap junctions: Cooperation of neighboring cells
Desmosomes: Spot desmosome Belt desmosome
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Harper’s P479 Fig 43-12
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Harper’s P480 Fig 43-13
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Harper’s P482 Fig 43-16
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Harper’s P485 Fig 43-19
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Peck Ritter P368 Fig 9.34