BICD 110 Lecture Notes - Lecture 2: Sphingomyelin, Positron Emission Tomography, Broad Peak
28 Jun 2018
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BICD110 Lecture 2 Notes 4/5/18: Membranes. From the basics to cancer detection/treatment
- Cell separated from environment by membranes. Membranes protect from environment
and isolate specific cellular functions from one another. Bring order to the cell
- Membranes are very fluid
oLaser tweezers: can point lasers to pull at part of membrane to bring them apart, but
not break them. The membrane components move quickly to adapt to the distortion of
the layers. Only things that hold membranes together are non-covalent interactions.
Can look at mitosis and pull chromosome off spindle to study
- All biological membranes are:
oMade of lipids and proteins
oHeld together by non-covalent bonds
- Properties of membranes
oBarrier: to isolate processes
Lipids provide barrier and flexibility of barrier
Proteins provide selectivity
oA rigid structure, but flexible and dynamic
- Typical cell’s plasma membrane: 50% lipids and 50% proteins by mass
oMany more lipids (109), because smaller in size
- Bilayers
oEarly theoretical models for membrane structure
oBasic structure of cell membranes: fluid mosaic model
Different parts put together to make a whole. Fluid because
proteins and lipids can move around through the membrane
oSupporting evidence for bilayer
X-ray diffraction: looking at patterns suggested dense
line, less dense line, followed by dense line. Head
groups must be lined up at the top and bottom
Transmission EM (2D): stain polar head groups of phospholipids in plasma
membrane of RBCs with osmium. Looked like railroad tracks (2nm distance, fit with
length of fatty acid tails)
Freeze-fracture EM (3D): membrane split in between
phospholipids
o3 major types of lipids in membranes: all amphipathic
phospholipids (phosphoglycerides): 2 fatty acid tails connected to glycerol, and 3rd
glycerol connected to phosphate head group
cholesterol
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Document Summary
Membranes protect from environment and isolate specific cellular functions from one another. Membranes are very fluid: laser tweezers: can point lasers to pull at part of membrane to bring them apart, but not break them. The membrane components move quickly to adapt to the distortion of the layers. Only things that hold membranes together are non-covalent interactions. Can look at mitosis and pull chromosome off spindle to study. All biological membranes are: made of lipids and proteins, held together by non-covalent bonds. Properties of membranes: barrier: to isolate processes. Proteins provide selectivity: a rigid structure, but flexible and dynamic. Typical cell"s plasma membrane: 50% lipids and 50% proteins by mass: many more lipids (109), because smaller in size. Bilayers: early theoretical models for membrane structure , basic structure of cell membranes: fluid mosaic model. Different parts put together to make a whole. Fluid because proteins and lipids can move around through the membrane: supporting evidence for bilayer.
