Membrane Composition and Structure

Question 1

Membranes are composed of lipids, proteins, and carbohydrate containing molecules. The carbohydrate portions are covalently bound to either ____ or ____

Answer 1

proteins (glycoproteins) or lipids (glycolipids)

Question 2

Compounds soluble in organic solvent are called ___

Answer 2

lipids

Question 3

True or false? the relative amounts of protein and lipid varies from membrane to membrane

Answer 3

true

Question 4

A membrane that has a high protein to lipid ratio would be found where?

Answer 4

mitochondrial inner membrane

Question 5

A membrane that has a low protein to lipid ratio would be found where?

Answer 5

myelin

Question 6

All of the membrane lipids are “amphipathic”. Explain what this means.

Answer 6

one part is hydrophilic: phosphate, amino acid derivatives, and carbohydrate
the other part is hydrophobic: the fatty acid

Question 7

The head group in membrane lipids is ___, while the hydrocarbon tail is ___

Answer 7

polar; nonpolar

Question 8

What is different about the hydrocarbon tails in saturated fatty acids than in unsaturated fatty acids?

Answer 8

saturated: tails are straight
unsaturated: tails have kink

Question 9

Membrane lipids can spontaneously form “____” which are similar to a membrane

Answer 9

liposomes

Question 10

____ proteins require detergents to separate them from the membrane

Answer 10

integral

Question 11

Integral proteins interact extensively with the ____ ___ of the membrane

Answer 11

hydrophobic core

Question 12

Integral proteins usually span the membrane. The membrane spanning domains may also be in the form of ____.

Answer 12

Beta-sheets

Question 13

___ proteins do not require detergents to separate them from the membrane

Answer 13

peripheral

Question 14

Plasma membrane is characterized by the greatest amount of ____

Answer 14

cholesterol

Question 15

Cardiolipin is restricted to ____ membrane

Answer 15

mitochondrial

Question 16

Plasma membrane phospholipids are found randomly in the membrane. True or false?

Answer 16

false; are not found randomly

Question 17

PC and sphingomyelin are located primarily in the ____ ____ of the plasma membrane

Answer 17

outer leaflet

Question 18

___ and ____ are located primarily in the inner leaflet of the plasma membrane

Answer 18

PS; PE

Question 19

Lateral movement of phospholipids is common, but movement from one leaflet to the other occurs only rarely.. There are enzymes that catalyze the movement of lipid from one leaflet to the other. These enzymes are responsible for maintaining the lipid ____ of the plasma membrane

Answer 19

asymmetry

Question 20

The _____ portion of glycolipids extends only into the extracellular space. Therefore these lipids are restricted to the outer leaflet of the plasma membrane

Answer 20

carbohydrate

Question 21

Protein orientation is greatly associated with the ____ of the protein

Answer 21

function

Question 22

True or false? Proteins in membranes may be anchored by interaction with other cellular elements either outside or inside of the cell.

Answer 22

true

Question 23

Various regions of a membrane may be associated with a specialized function. These regions may not only have a specific protein composition, but may have a ____ composition which differs measurably from the rest of the membrane

Answer 23

lipid

Question 24

Bilayer lipids under most physiological conditions can exist in either a _______ phase or in a ___ phase

Answer 24

liquid-crystalline; gel

Question 25

For any given composition of lipids, there is a temperature at which this phase transition occurs, called the ___ temperature

Answer 25

transition

Question 26

The lipid bilayer is ___ permeable to small molecules when in the gel phase

Answer 26

less

Question 27

Unsaturated fatty acids have a ____ melting temperature

Answer 27

lower

Question 28

Increasing the unsaturated fatty acids in phospholipids ____ the membrane fluidity

Answer 28

increases

Question 29

One function of cholesterol appears to be to modulate the ____ of the membrane.

Answer 29

fluidity

Question 30

At temperatures below the Tm, cholesterol ___ the fluidity, and at temperatures above the Tm, it ____ the fluidity

Answer 30

increases, limits

Question 31

Membrane permeability is simple diffusion, non mediated. This means it is restricted to what type of molecules? give examples

Answer 31

hydrophobic molecules or small uncharged, polar molecules | ex: H2O, O2, CO2, Urea

Question 32

A channel protein with a water-filled pore is an example of what type of diffusion?

Answer 32

simple

Question 33

Channel proteins display exquisite ____ in the molecule they allow through the pore

Answer 33

selectivity

Question 34

Describe facilitated diffusion

Answer 34

proteins do not form pores, but interact with the transported molecule and due to some change in the molecule-protein complex, release the molecule on the opposite side of the membrane

Question 35

Mediated transport may be classified as electroneutral or electrogenic. Explain each one.

Answer 35

electroneutral: transport results in no difference in charge electrogenic: transport results in charge difference across membrane

Question 36

The Na+, K+ ATPase is responsible for transporting ___ Na+ out of the cell, as it transports ___ K+ into the cell at the expense of 1 ATP

Answer 36

3; 2