Lecture 3 Flashcards
The cell membrane is composed of
a phospholipid bilayer
phospholipid structure
- cylindrical / stackable
- amphipathic
- hydrophilic phosphate head
- hydrophobic fatty acid tails (2/double)
how do phospholipids respond to water
they will spontaneously self assemble into a bilayer because they are amphipathic and cylindrical/stackable
micelle
a circular shape of single tailed phospholipids in the presence of water
because of their cone shape (conical)
how do single tailed phospholipids respond to water
form a micelle because of their conical shape
lateral movement
moving side to side / horizontal translation type of movement
phospholipids have rapid and frequent lateral movement
provides fluidity and flexibility to the membrane
flip/flop movement
when phospholipids will flip so it is on the opposite side of the bilayer
rare to happen spontaneously because of the hydrophobic core
occurs with the help of flippases
flippase
an enzyme that helps phospholipids have flip/flop movement
hydrophobic core
the core of hydrophobic fatty acid tails of phospholipids
prevents polar molecules from crossing
do bonds hold the phospholipid bilayer together?
no, it is only hydrophobic and hydrophilic associations
how does high temperatures affect membrane fluidity
phospholipids have more kinetic energy + move faster
gap between phospholipids increases
↑permeability ↑fluidity ↓integrity
how can cells adapt their cell membrane for high temperatures
- increase hydrocarbon tail length (↑hydrophobicity to more strongly associate/hold together)
- decrease C═C (unsaturated) so the tails are straight and more stackable near each other
- increase cholesterol to increase hydrophobicity and acts as a speed bump
how does low temperatures affect membrane fluidity
gap between phospholipids decreases
↓permeability ↓flexibility
how can cells adapt their cell membrane for low temperatures
- increase C═C (more unsaturated HC chains) -> kink in chains will force a gap between phospholipids
- decrease hydrocarbon tail length (↓hydrophobicity so less associations binding the phospholipids together)
- increase cholesterol (acts as a spacer between phospholipids
Fluid Mosaic Model
a model of the phospholipid bilayer that states the membrane is a fluid structure (phospholipids) with a mosaic of different proteins embedded in or attached to a double bilayer of phospholipids
