Chapter 9- Lipid Membranes Flashcards by Ty Nicholas

Lipids ____ in water due to ____

aggregate
hydrophobic interactions

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Lipids aggregate can form:

Micelles
Bilayers
Vesicles

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Single tailed amphiphiles form ____ because of their ______

spheroidal or ellipsoidal micelles
conical shapes

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Amphiphile monomers do not form micelles until they surpass a ______

certain concentration

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Critical micelle concentration (CMC) definition

concentration above which micelles form

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Above CMC =
Below CMC=

mostly monomers
mostly micelles

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CMC is a measure of the strength of _____

amphiphile association

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Low CMC means

strong association (micelle forms at low concentration)

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High CMC means

weak association (micelle forms at high concentration)

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Lipid Properties Influencing CMC

Charge
Aliphatic chain length
unsaturation
ionic strength

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How does charge affect CMC

charge raises CMC because electrostatic repulsion requires a higher concentration to overcome

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How does chain length affect CMC?

the longer the chain, the lower the CMC (association more favorable)

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How does unsaturation affect double bonds?

more double bonds mean higher CMC (more difficult to associate)

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How does ionic strength affect CMC?

higher ionic strength means a lower CMC

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Which lipids tend to form bilayers?

Sphingolipids and glycerophospholipids (due to their cylindrical shape)

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the thickness of the lipid bilayer tails and heads? overall?

~15 A
~60 A

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Membranes can form different fluidity phases like:

solid- ordered
liquid-disordered

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Solid-ordered lipid bilayer characteristics:

straight rigid acyl chains
proteins + lipids fixed in place

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Liquid-disordered lipid bilayer characteristics:

wiggling disorderly acyl chains
proteins and lipids move
typical for unsaturated acyl chains

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The temperature required to induce the liquid-disordered phase is:

phase transition temp

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Unsaturated and short chains make membranes more ____ at lower temp

fluid

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Liquid ordered phase is induced by ____ and is a hybrid of ___

cholesterol
liquid disordered and solid phases

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liquid-ordered phase characteristics

straight acyl chains
proteins and lipids move
much of plasma membrane is like this

Role cholesterol plays in membranes

maintain bilayer in fluid-like state
needed for biological functions

Cholesterol _____ fluidity under the Tm and ______ fluidity over the Tm

increases decreases

types of Lipid bilayer dynamics

1. lateral diffusion 2. transverse diffusion

Lateral diffusion is a very ____ process

fast

What is lateral diffusion?

a lipid moves across the bilayer

how can the rate of lateral diffusion be determined experimentally?

single particle tracking of labeled lipids

Transverse diffusion is an extremely ____ event

rare

What is transverse diffusion?

transfer of lipids across the bilayer

Why is transverse diffusion unfavorable?

polar head must diffuse through the hydrocarbon core

Transverse diffusion is a very ____ process

slow

The extracellular leaflet has an overall ____ charge

neutral

the extracellular leaflet is enriched in

- Sphingomyelin and phosphatidylcholine - glycolipids in the outer leaflet

The cytosolic leaflet is enriched in:

more negative charges present

Bilayer permeability depends partly on ___ but mostly on ____

size hydrophobicity

____ and ____ molecules diffuse across the lipid bilayer

small hydrophobic

Lipid bilayers of highly impermeable to ____ molecules

charged

Transport proteins lower ______ of molecules crossing the bilayer

activation energy

Polar molecules have _____ when crossing the membrane

extremely high energy of activation

Transporter proteins can facilitate ____ across the membrane

facilitate

Types of membrane proteins

1. integral membrane proteins 2. peripheral membrane proteins

Integral membrane proteins reside ____

in the membrane

Peripheral membrane proteins are found ____

attached to the membrane through a covalently attached lipid chain

Since integral proteins reside within the bilayer they are:

- hydrophobic - insoluble in aqueous buffer - need detergents to be solubilized

Residues found in transmembrane domains:

V, M. F, I, and L

transmembrane domains often form ___

alpha helices

How many residues span the hydrophobic core of a transmembrane domain

~20

How can helical transmembrane domains be predicted?

hydropathy plot for protein of interest

Beta barrel membrane protein characteristics

- every other residue interacts with lipids - only 7-9 residues span the hydrophobic core

Peripheral membrane proteins are typically water ____

soluble

Peripheral membrane proteins are associated through:

- electrostatic interactions - H-bonding

Association of peripheral membrane proteins is generally ____ and is often ____

reversible regulated

peripheral membrane proteins can associate through ___ helix which has:

an amphipathic 1 hydrophobic face and 1 polar face

attachment of lipid ____ can alter the properties and localization of proteins

moieties