Module 9 - 2

Question 1

What are membranes primarily composed of?

Answer 1

Lipids and proteins.

Question 2

What is the role of proteins in membranes?

Answer 2

Reception and other active roles.

Question 3

What is the relationship between membrane activity and protein to lipid ratio?

Answer 3

More active membranes have a higher ratio of protein to lipid.

Question 4

Can the composition of membrane components be dynamic?

Answer 4

Yes, particularly for prokaryotes.

Question 5

What is the fluid mosaic model of membrane structure?

Answer 5

a model describing biological membranes as a fluid bilayer with embedded proteins; The bilayer exhibits both structural and functional asymmetry

Question 6

What causes membranes to be dynamic

Answer 6

the nature of the non-covalent interactions

Question 7

Is lateral movement of proteins and lipids within the membrane slow or rapid?

Answer 7

Rapid.

Question 8

Is movement across the membrane restricted or unrestricted?

Answer 8

restricted

Question 9

What is transbilayer movement require?

Answer 9

A polar head group to pass through the hydrophobic environment

Question 10

Is the uncatalyzed rate of lipid molecule crossing from one sheet to the other fast or slow?

Answer 10

Very slow.

Question 11

What are flippases?

Answer 11

Enzymes that catalyze translocation of lipids from one side of bilayer to the other.

Question 12

Can the lipid composition of the inner and outer sheets of the bilayer be different? What does this allow for?

Answer 12

Yes. It allows for specialization of the membrane faces

Question 13

Why do cells need to maintain appropriate levels of membrane fluidity?

Answer 13

To ensure proper function.

Question 14

Do membranes undergo temperature-dependent phase transitions?

Answer 14

Yes

Question 15

What happens to the membrane below the phase transition temperature?

Answer 15

It becomes too solid.

Question 16

What happens to the membrane above the phase transition temperature?

Answer 16

It becomes too fluid.

Question 17

What happens to the membrane at the phase transition temperature?

Answer 17

The hydrocarbon chains are partially ordered but lateral diffusion is still possible. (Just right)

Question 18

How do cells adjust membrane composition to maintain liquid-ordered state?

Answer 18

Bacteria vary the length and saturation of the hydrocarbon tails of membrane lipids; animals use cholesterol to mediate membrane fluidity

Question 19

Can temperature cause changes to membrane composition?

Answer 19

Yes.

Question 20

Can membrane structure and function be specialized?

Answer 20

Yes.

Question 21

What are the mechanisms to enable specialization in the bilayer?

Answer 21

Composition and distribution of membrane components and specialized membrane regions

Question 22

What are the components of the membrane?

Answer 22

lipid and protiens

Question 23

How are membrane components distributed?

Answer 23

Static and dynamic

Question 24

What are lipid rafts?

Answer 24

Plasma membrane microdomains, rich in cholesterol and sphingolipids, which provide a particularly ordered environment

Question 25

What is the composition of lipid rafts?

Answer 25

Sphingolipids with longer tails that exclude glycerophospholipids

Question 26

What is the function of lipid rafts?

Answer 26

Docking points for lipid-anchored proteins that contain long chain saturated fatty acid anchors and the lipid linked proteins that associated with rafts often serve signaling functions

Question 27

What are the three categories of membrane proteins?

Answer 27

Peripheral (c and d), lipid-anchored (e), and integral membrane proteins (a and b)

Question 28

What are the active roles of membrane proteins?

Answer 28

Receptors and transporters

Question 29

How do peripheral membrane proteins associate with the membrane?

Answer 29

Through electrostatic or hydrogen-bonding interactions

Question 30

Where are the bulk of peripheral membrane proteins located?

Answer 30

In the cytosol or extracellular space

Question 31

What releases peripheral membrane proteins from the membrane?

Answer 31

Changes in pH or ionic strength

Question 32

What are lipid-linked proteins?

Answer 32

Proteins that associate with rafts and contain long-chain saturated fatty acid anchors

Question 33

What are the specialized compositions and functions of membranes?

Answer 33

Varies across species and cell types

Question 34

What are the dynamic changes to membrane composition and/or positioning used for?

Answer 34

To regulate biological events

Question 35

What is an example of dynamic changes to membrane composition?

Answer 35

Movement of phosphatidylserine to outer leaf functions in initiating cell destruction (apoptosis)

Question 36

What are the hydrocarbon tails of sphingolipids like?

Answer 36

Longer and saturated

Question 37

What makes lipid rafts thicker and more ordered than the rest of the membrane?

Answer 37

The stable associations formed by the longer, saturated hydrocarbons of sphingolipids

Question 38

Lipid rafts arise from what original

Answer 38

These spontaneous association of lipid molecules whose hydrocarbon tails are of similar length