Ch 1.5 Membranes Flashcards
What is a defining feature in membranes
-made from amphipathic lipid bilayer and proteins
Why are membranes importent?
3 points
- dynamic cells require them to form, reseal, bud, fuse.
- separation from the surrounding aqueous environment
- lipids are flexible and can interact with other molecules (protein, carbohydrates)
What is the fluid mosaic model?
-cuz membranes are made of phospholipids embedded with proteins
What do lipids do in the membrane
Provide permeability barrier/ fluidity
What do proteins do in the membrane?
- they transport, work as enzyme, receptors etc.
Why are lipids hydrophobic?
- Water molecules will condense around the tails
- when the tails are closer together the water molecules are more free (more disorders so energetically favorable )
What is enthalpy?
- energy
- mesures how strongly bonded the system is
What is entropy?
- randomness
- the freedom of movement
Are bilayers formes more by entropy or enthalpy?
Entropy ( increases freedom of water)
What are the 2 factors that form membranes?
- Increase enthalpy in water (lots free motion)
2. ID-ID between tails ( many of them so stable)
Is the formation of membranes spontaneous?
Yes (- delta G)
What are the 3 types membranes and what are the structure of lipids in them?
- Wedge shape with large head and 1 tail = Micelle: sphere with tails in the center and heads outside
- Cylindrical with smaller head and 2 tails= bilayer: tails in the inside heads outside
- Two tails can also be = liposome: spherical with aqueous inside
What do cells membranes have in them that lab made liposomes don’t?
Membranes have proteins
What’s more fluid saturated or unsaturated?
Unsaturated are packed looser so it’s more fluid.
What properties of lipids dictate the properties of properties membrane?
-Chain length , degree of saturation, head groups
