Bio 353_ Lecture 2%2F13%2F18 - 2%2F20%2F18.docx - Membrane...

This preview shows page 1 - 3 out of 5 pages.

The preview shows page 1 - 3 out of 5 pages.
Membrane Functions-Boundary and permeability barriers; results in compartments-Working platforms/surface area (e.g ER, thylakoid membranes) -Regulates transport of molecules and ions-Signaling (e.g. detect and transmit electrical and chemical signals) -Cellular growth and motilityPhospholipids: -Major component of animal cell membranes-Most are phosphoglycerides-Two -OH groups of glycerol are linked to fatty acids, the third - OH is linked to a phosphoric acid and to one of a variety of small polar groups-> NOTE- the length fatty acid tails and amount of fatty acid saturation contributes to membrane fluiditySphingolipids (from mythological Sphinx)-Derived from sphingosine, not glycerol like-In mammals play important roles in signal transmission, cell recognition, cell surface protections; also found in fungi (roles in regulation of endocytosis and cytoskeleton) -Often, but not exclusively, found in neural tissues, discovered in brain tissue extracts-Sphingomyelin: a type of sphingolipid found in animal membranes, especially membranous myelin sheath surrounding nerve cell axons; in humans, sphingomyelin is believed to be the only cell membrane phospholipid not derived from glycerol-Several disorders of sphingolipid metabolism, known as sphingolipidoses. For example, Tay-Sachs disease: a genetic disorder caused by insufficient activity of an enzyme that breaks down sphingolipids. The build up of these lipids gradually destroys brain and nerve function; Tay-Sachs disease occurs most frequently in descendants of central and Eastern european Jewish populations (Ashkenazi Jews)->>enzyme replacement therapy is available to treat some forms of sphingolipidoses, other types are generally fatal by age 1 to 5 years oldGlycolipids: (= glycosylated lipids) -Function of glycolipids (and glycoproteins) -Protection: strengthens and protects plasma membrane-Cell recognition: attack pathogens, organ/tissue graft compatibility, fertilization, blood transfusions, tissue grafts and organ transplants, embryonic development Membrane Architecture-Amphipathic phospholipids spontaneously form bilayer in water-The battle between polarity and nonpolarity is resolved for phospholipids by forming a lipid bilayer (= two monolayers)Membrane Biogenesis-Phospholipid synthases bound to the cytosolic monolayer of the smooth ER manufactureand insert new phospholipids into the cytosolic monolayer-Symmetrical growth of bilayer is established by the action of phospholipid translocators (flippases, floppases, scramblesases) that flip phospholipids (cholesterol too) -Occurs primarily at ER, also Golgi and plasma membrane-Glycolipids are NOT flipped-Phospholipids translocators reduce time of phospholipid flipping from days to minutesThe symmetry of Membranes
-

Upload your study docs or become a

Course Hero member to access this document

Upload your study docs or become a

Course Hero member to access this document

End of preview. Want to read all 5 pages?

Upload your study docs or become a

Course Hero member to access this document

Term
Spring
Professor
Banker

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture