BISC 307L 1st Edition Lecture 2 Current Lecture Membrane Dynamics Transport across membranes o 1 Direct o 2 Facilitated Diffusion o 3 Osmosis o 4 Ion Channel o 5 Active transport o 6 Exo and Endocytosis o Diffusion is affected by 1 Concentration 2 Distance 3 Temperature 4 C S Area 5 Molecular Size 6 Lipid Solubility Facilitated Diffusion o Glucose Transporter is an example o Simply due to concentration difference passive transport o Bidirectional Transport o Five types 1 GLUT1 Transports glucose mainly but also galactose Used by many cells glycogenolysis 2 GLUT2 transports glucose galactose and fructose high capacity but low affinity insulin and glucose concentration sensing mechanism small intestine liver glucose sensor in pancreatic beta cells 3 GLUT3 Transports mostly glucose but some galactose Main transporter for neurons because have high metabolic rates and need a lot of glucose 4 GLUT4 Transports only glucose Insulin responsive The only one that is inserted in the membranes in response to insulin glucose uptake In skeletal and cardiac muscle adipocytes 5 GLUT5 Fructose transporter Main energy source for sperm
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