Biological Membranes

lipid

Membranes are complex _______- based structures that form pliable sheets

it's surroundings

All cell membranes separate the cell from ?

organelles

Eukaryotic cells have various internal membranes that divide the internal space into compartments known as...

1. define boundaries of the cell

2. allow for import and export of selective nutrients and waste

3. retain metabolites and ions within the cell

4. Sense external signal and transmit information into the cell

5. provide compartmentalization within the cell (seperate energy producing reactions from energy consuming ones)

6. produce and transmit nerve signals

7. store energy as a proton gradient

8. support synthesis of ATP

What are the 8 functions of membranes?

1. micelles

2. bilayers

3. liposomes

Lipids will aggregate into structures in water. What are three major structures that are observed?

1. type of lipid

2. concentration

The structure of the lipid formed in water depend on what two traits?

amphipathic

Micelle is formed in the solution of __________ molecules.

fatty acids and sodium dodecyl sulfate

Micelles have larger more polar heads than tails. What are the tails made of?

a few dozen to a few thousand

How many lipid molecules are micelles composed of?

two leaflets of lipid monolayers

The membrane bilayer consists of

phospholipid and sphingolipids

What two molecules will cause the spontaneous organization of a lipid bilayer?

spherical; concentration

Liposomes (vesicles) are small bilayers that will spontaneously seal into a ____________ vesicles in a ______________ dependent manner

These vesicles can be made in vitro and the central aqueous cavity can dissolve drugs or viruses which will allow it to go through the lipid membrane. The vesicle can then fuse with the membrane.

Why are micelles used as artificial carriers?

bimolecular sheets

Is bimolecular sheets or micelles favored in the formation of a lipid bilayer?

no they are asymmetric

Are membranes symmetric?

1. enzymes

2. gates

3. pumps

4. energy transducers

5. receptors

Membrane proteins serve as what 5 things?

Sphingolipids

Cholesterol

Phosphatidylcholine (PC)

What are the three main components of a membrane?

Phosphatidylcholine (PC)

What molecule is in promident amounts in different membrane types?

the amount of Phosphatidylcholine (PC) to cholesterol

The structure and fluidity of a membrane is mainly determined by ...

non-covalent

The interaction between lipids and proteins are

glycerol + two fatty acids + phosphorylated alcohol

What is a phosphoglyceride?

Phosphatidylserine

What is this phosphoglyceride?

Phosphatidylcholine

What is this phosphoglyceride?

Phosphotidylinositol

What is this phosphoglyceride?

Phosphatidylethanolamine

What is this phosphoglyceride?

Sphingosine

What is sphingomyelin derived from?

triacylglycerol (no hydrophilic component)

What are the only neutral lipids?

ether bonds are more resistant to cleavage

What is the significance of ether bonds in lipids?

7

Up to how many sugars can be attached to glycolipids?

Sphingosine

Glycolipids are derived from?

covalently

Are glycolipids covalently bound or non-covalently bound to sugars?

The more fluid a membrane is the more cholesterol it has

the more rigid a membrane is the less cholesterol it has

How does cholesterol related to membrane fluidity?

ridig

when cholesterol is decreased it can cause muscles to become more

integral are firmly associated

peripheral are loosely associated

Describe the association to the membrane between integral proteins and peripheral protein

on the extracellular component

Where are carbohydrates located on the membrane?

yes via chemical treatment by piercing the membrane

Can permeability be increased?

yes - butter is a example of how membranes can undergo phase transitions

Can membranes exist in various phases and undergo phase transition?

ions ( K+, Na+, Cl-)

What molecules would need a channel to get through the membrane?

large uncharged polar molecules

What molecules would need a transporter to get through the membrane?

hydrophobic molecules

small uncharges polar molecules

What molecules can go through the membrane via simple diffusion?

SDS-PAGE electrophoresis

What technique can be used to analyze membrane proteins?

free- energy barrier

What prevents membrane proteins from rotating?

non-GPI linked can be dissociated from the membrane fairly easily during changes in ionic strength

GPI- linked proteins are linked to the membrane during specific regulatory events and can be reversibly removed

What is the difference between a non-GPI linked and GPI- linked peripheral protein?

in the presence of strong detergents

How would integral proteins be removed?

removed by disrupting ionic interactions either with high salt or pH changes

How are peripheral proteins removed?

any lipids

If the protein is purified then it is no longer associated with

amphitropic

GPI - linked proteins are also called

covalent

Amphitropic proteins are attached by what kinds of interactions with lipids/ carbohydrates?

attachment to, or cleavage from lipids

The biological regulation of amphitropic proteins result in

no different proteins for different domains

Are there all the same integral proteins throughout the membrane?

asymmetric ( like the membrane)

Are integral proteins symmetric or asymmetric?

phospholipids

Purified integral proteins still have ____________ attached.

how many times a protein spans the lipid bilayer

What does a hydropathy plot tell you?

~ 20 alpha helices

The transmembrane region consists of how many residues?

anion

___________ channels are formed by several transmembrane alpha- helices

Glycophorin high charge keep the RBC from adhering to the inside of the vessel wall and allow for it to move freely

Explain glycophorin's effect on red blood cells

120 days

What is the life span of RBC's?

outer:

phosphatidylcholine (PC), sphingomyelin (SM)

inner:

phosphatidylethanolamine (PE), phosphoinositol (PI), phosphatidylserine (PS)

What are the components of the outer and inner membrane of RBC's?

bind extracellular matrix proteins to microfilaments of the cytoskeleton via intracellular attachment proteins

What do transmembrane linker proteins do?

diversity that aids in cell to cell interactions and cell-specific properties

The diversity of integrin heterodimers contribute to

extracellular divalent cations

What does the ligand binding to integrin depend on?

integrin to actin microfilaments

Binding sites of cytosolic intergin tail interacts with intracellular attachment proteins to link

secrete less fibronectin and increased migration and proliferation

What does cancer like cell secrete less of and how do they behave differently?

liquid ordered: gel phase- individual molecules do not move around

liquid disordered: fluid phase- individual molecules move around

Depending on the temperature and composition the membrane can be in a gel phase or fluid phase.

What is the difference between the liquid- ordered stage and liquid disordered stage?

fluid- like

Under physiological conditions what phase does the membrane favor?

fatty acid composition and melting point

Membrane fluidity is mainly determined by

more

Membranes that have shorter and more unsaturated fatty acids will be __________ fluid.

decreases

Melting point __________ as double bonds are added.

saturated

At higher temperature cells need longer more ____________ fatty acids.

unsaturated

At lower temperature cells need more ___________ fatty acids