BIOL300: Chapter 11

True or false: we have membranes only on the inside of the cell.

false: we have membranes on both the outside and inside

What are the three things membranes are important for?

1. receiving communication

2. import and export

3. movement

What is a common term for the lipid bilayer that describes its diverse and dynamic structure?

Fluid Mosaic

Does the outer membrane exist on its own?

no, there is a structure of proteins that help stabilize it.

what us the most common phospholipid in the cell membrane?

phosphatidylcholine

what term can we describe to use phospholipids because they have polar and nonpolar regions?

amphipathic

what region of the phospholipids are polar?

their heads

what region of the phospholipids are nonpolar?

their tails

do membranes require energy to aggregate?

no, membranes will aggregate on their own without the presence of energy or enzymes.

hydrophobic

water fearing- uncharged and nonpolar

hydrophilic

water loving- charged and polar

can life exist without the presence of water?

no, all life requires water

phospholipid bilayers spontaneously close in order to make sealed compartments that are

energetically favorable

liposomes

artificial lipid bilayer that can be used for drug and vaccine testing

what are the four types of movements that phospholipids do in the cell membrane?

lateral diffusion, flip flop, flexion, and rotation

lateral diffusion

moving past one-another -> REQUIRES NO ATP OR ENZYME

flip flop

flipping between membrane sides -> REQUIRES ATP AND ENZYMES

what enzyme does aids in flip flop?

flippase

flexion

standing in place while tails are moving -> REQUIRES NO ATP OR ENZYME

rotation

staying in place and spinning -> REQUIRES NO ATP OR ENZYME

What is a lipid raft?

a group of lipids that float together as a unit within a larger sea of lipids (usually perform some sort of cell signaling)

What are the two properties of the hydrocarbon phospholipid tails that affects membrane fluidity and permeability?

length and number of double bonds they contain

longer tails means...

less permeability and fluidity

more double bonds in the phospholipid tails means ....

more permeability and fluidity

cholesterol makes up about how much of the membrane?

20%

Is cholesterol amphipathic?

Yes

What does cholesterol do for the membrane?

- fills spaces between the phospholipids

-stiffens the bilayer in animals at room temp

True or false: the lipid bilayer is symmetrical

False, asymmetrical

Where does new membrane synthesis occur?

the ER

How much os the plasma membrane is proteins?

50%

transmembrane proteins

Integral proteins that span the membrane.

monolayer associated proteins

alpha helix proteins exposed on the surface

Lipid-linked proteins

not actually in the membrane but covalently linked to a lipid on the membrane

protein-attached proteins

These proteins are attached to the membrane only by relatively weak, noncovalent interactions with other membrane proteins.

The backbone of every protein is identical and ...

HIGHLY CHARGED

true or false, proteins decrease cell signaling

false, they make increase signaling and make it faster

What do detergents do?

They break up the lipid bilayer which allows a release of proteins

detergents are amphipathic and...

their hydrophobic ends bind to the cell membrane

what is the cell cortex

a network of proteins that sits under the bilayer to give it shape and support.

what is an example of a cell cortex?

the spectrin network of red blood cells

What are the four ways of restricting protein movement?

1. tethering them to something on the inside of the cell

2. Attach them to the outside of the cell

3. Attach them to other cells

4. Tight junctions- (road blocks)

what are membrane domains?

functionally specialized regions on the cell or organelle surface where you can find certain proteins

The carbohydrate layer of the plasma membrane is also known as the

sugar layer

What are sugar chains called?

oligosaccharides

what are the three main functions of the carbohydrate layer of the membrane?

1. protection

2. energy source in extreme conditions

3. cell-cell recognition and adhesion