BI111 Lecture Notes - Lecture 14: Amphiphile, Hydrophile, Transmembrane Domain

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2 Dec 2016
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Lecture 14- Bi110
Integral membrane proteins are amphipathic
- Integral: integrated in the membrane
- Transmembrane domain: chains that stretch across the membrane (single or multiple)
- Typically, there are ±20 amino acids to get across
- With the ones of the either less or more, they can have shorter phospholipid making it more or
longer depending on thickness and size
Frye ad Edidi’s Experiet
- Stated isolated cells (cultured from other cells) from mice and human
- Critical part labelled the cells with fluorescent dyes
- Green: Mice Red: Human
- Mixed them together in a certain condition
- Formed a large hybrid cell (half red and half green)
- 40 min 37C found- no longer red or green but an even distribution of both colours
- Applies to all membranes
Membrane Fluid
How fluid?
- More dense the phoslip.b tight pack= less fluid
- Less dense packed =more fluid
- Composition (how they are made)
- Temperature
- Why? Molecules cant pass through
- Maintain functions
- Too fluid loses important molecules
Effect of unsaturated fatty acids on packing of membrane lipids (composition)
- Saturated: Single bonds, denser, less space, straight chains, less fluid, tighter packing
- Unstaturated: double bonds, less dense, more space (in the mono un.s. there is the kink), fluid
becomes higher
- Viscous: not very fluid
- (think of butter: cold hard- warm fluid)
- Sat: if in temp, it will be much more solid in cooler in higher it wont like the temp. and needs
Temperature
- Alter their composition to maintain their fluidity
Sterols:
- Help maintain their fluidity
- It acts as the buffer
- No sterols: too leaky or too solid
- It can maintain in the larger in temperature range
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