Biology 1002B Study Guide - Quiz Guide: Chief Operating Officer, Phosphatidylinositol, Cytoskeleton
Fluid Mosaic Model
-Fluid: Flexible and dynamic.
o Lipid molecules vibrate, flex, spin, moves laterally rapidly
o Keeps membrane dynamic.
• Rarely do the lipids flip from one layer of the bilayer to the other.
o Requires energy. Used to maintain asymmetry of bilayer.
-Mosaic: Variety of components within the membrane.
• Can contain diff. phospholipids, glycolipids, sterols, proteins, etc.
• Phospholipid diversity:
o Different levels of saturation (# and position of DB) in tails
o Different lengths of tails -Different heads
Types of Phospholipids
• Main structure: Polar head: + Hydrocarbon tails
• Amphiphatic with polar (hydrophilic) head and non-polar (hydrophobic) tails
4 Main types:
1. Phosphatidylethanolamine: Has ethanolamine attached to phosphate.
• Confers positive charge and found mostly on outer layer of membrane.
2. Phosphatidylserine: Has serine attached to phosphate.
• Confers more negative charge.
• More common on inside layer.
3. Phosphatidylcholine: Has choline attached to phosphate
• Confers positive charge and found mostly on outer layer.
4. Sphingomyelin:
• Sphingosine(not glycerol) backbone + Phosphocholine head + HC Tail
• Less common. -Diff. # depending on cell types.
Sterols in Membrane:
-Embedded in membrane. -Maintains fluidity but providing buffer to temperature
changes.
Membrane Asymmetry
-Uneven distribution of phospholipids in the two layers
-Outer layer has mostly negatively charged phospholipids. Inside layer→ Positive
-”Flip-flop”: Translocating phospholipids from one layer to another to maintain asymmetry.
-Glycolipids found mostly on outer layer.
Membrane Fluidity
• Temperature:
• Cold: Rigid. Phospholipids more tightly packed.
o Hot: Phospholipids spread out and more fluid.
• Chain length and saturation:
o Less saturation=more dense=less fluid
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Document Summary
Fluid: flexible and dynamic: lipid molecules vibrate, flex, spin, moves laterally rapidly, keeps membrane dynamic, rarely do the lipids flip from one layer of the bilayer to the other, requires energy. Mosaic: variety of components within the membrane: can contain diff. phospholipids, glycolipids, sterols, proteins, etc, phospholipid diversity, different levels of saturation (# and position of db) in tails, different lengths of tails. Types of phospholipids: main structure: polar head: + hydrocarbon tails, amphiphatic with polar (hydrophilic) head and non-polar (hydrophobic) tails. 4 main types: phosphatidylethanolamine: has ethanolamine attached to phosphate, confers positive charge and found mostly on outer layer of membrane. Phosphatidylserine: has serine attached to phosphate: confers more negative charge, more common on inside layer. Phosphatidylcholine: has choline attached to phosphate: confers positive charge and found mostly on outer layer. Sphingomyelin: sphingosine(not glycerol) backbone + phosphocholine head + hc tail, less common. Uneven distribution of phospholipids in the two layers.
