Polvi lec #4

Question 1

What are the three classes of membrane proteins?

Answer 1

integral proteins
Peripheral proteins
lipid anchored proteins

Question 2

How are peripheral membrane proteins associated to the membrane? Are they hydrophobic or hydrophillic, why?

Answer 2

By weak covalent bonds, are mostly hydrophillic as they interact with the aqueous side of the membrane

Question 3

Are peripheral membrane proteins static or dynamic?

Answer 3

dynamic, they can be recruited to/released from the membrane

Question 4

What roles do peripheral membrane proteins have?

Answer 4

Have roles in signal transduction
Mechanical support for the membrane
Anchor for integral membrane proteins
and act as enzymes

Question 5

What is an example of peripheral membrane proteins? What do they do?

Answer 5

red blood cell peripheral membrane proteins, is a network of proteins that give blood cells their shape

Question 6

What is spectrin? Where are they found?

Answer 6

Plays a major role in red blood cells as they connect to membrane proteins to give flexibility and support to the cell, these are found on the cytoplasmic face of the membrane

Question 7

Where are lipid anchored proteins found?

Answer 7

They are found outside of the bilayer on either the extracellular or cytoplasmic side

Question 8

How are lipid anchored proteins attached to the bilayer?

Answer 8

They are covalently linked to a lipid molecule within the bilayer

Question 9

What are GPI-anchored proteins?

Answer 9

These are proteins attached to the membrane by a oligosaccharide that is linked to phosphatidylinsoitol (PI) in the membrane

Question 10

Where do GPI-anchored proteins face?

Answer 10

They face the extracellular space

Question 11

What are GPI proteins roles?

Answer 11

They have roles as receptors (take in incoming info from outside cell) and have roles in cell adhesion

Question 12

What lipid molecule are lipid anchored proteins linked to?

Answer 12

hydrocarbon chains embedded in the lipid bilayer on the cytoplasmic leaflet

Question 13

What roles does the hydrocarbon chains that lipid anchored proteins bind to have?

Answer 13

Has roles in signal transduction

Question 14

Can phospholipids move laterally within the same leaflet?

Answer 14

yes

Question 15

What is transverse diffusion? Why can’t phospholipids do this?

Answer 15

Is when phospholipids flip flop between leaflets, is thermodynamically unfavorable as bilayers are nonpolar in middle so polar head of phospholipid would have to go through that

Question 16

What enzyme can allow phospholipids to flip flop? What role does it have?

Answer 16

enzyme flippase, can play a role in establishing membrane asymmetry

Question 17

What are the six dynamics in which membrane proteins can move and be restricted?

Answer 17

random diffusion
can be immobilized
can move in one direction ( for ex: motor proteins)
Can be restricted by other integral membrane proteins
Can be restricted by membrane skeleton proteins
Can be restrained by extracellular materials

Question 18

What two types of transport is there across a membrane?

Answer 18

Passive and active

Question 19

Explain how membranes are selectively permeable barriers?

Answer 19

They allow some stuff to come through but stop some other stuff to come through

Question 20

What are the characteristics of passive transport?

Answer 20

Doesn’t need energy input from cell and occurs by diffusion

Question 21

What are the three types of passive transport?

Answer 21

through a membrane
through a channel
through a facilitative transporter

Question 22

What are the characteristics of active transport?

Answer 22

Does need energy input, and can move substances against a concentration gradient

Question 23

What are the types of active transport?

Answer 23

are types of pumps

Question 24

What is diffusion?

Answer 24

Is the spontaneous process in which substances move from an area of high conc to one of low until they hit equilibrium

Question 25

What is a concentration gradient?

Answer 25

The diff in the concentration of a substance between two areas

Question 26

What solutes can penetrate and diffuse through the lipid bilayer? Which ones can’t?

Answer 26

Can: Small inorganic solutes, such as O2, CO2, and H2O
* Solutes with high lipid solubility
Can’t: Ions and polar organic solutes (Eg: sugars and amino acids)
Anything too large

Question 27

What is osmosis?

Answer 27

When water moves through membrane from a region of lower solute concentration to a region of higher solute concentration

Question 28

Whats a hypertonic solution?

Answer 28

stuff outside cell more conc

Question 29

What’s a hypotonic solution?

Answer 29

stuff inside cell more conc, water rushes in, bursts

Question 30

What’s an istonic solution?

Answer 30

conc in cell and outside of cell equal

Question 31

What are two ways diffusion can happen through a channel?

Answer 31

Through an aquaporin or though an ion channel

Question 32

How does diffusion happen through an aquaporin?

Answer 32

aquaporins are proteins that facilitate the transport of water and aloo cells to be more permeable to water then just through diffusion

Question 33

What are ion channels?

Answer 33

are transmembrane structures that are highly selective and only allow certain ions to get through, most are gated (they change confirmation to open/close)

Question 34

What are the three types of ion channels in diffusion and their characteristics?

Answer 34

voltage gated- these open and close based on the ionic charge on either side of the membrane
Ligan gated- they open/close based on the binding of the ligand which is usually not the solute passing through the channel
Mechanogated- they open/close base don mechanical forces (for ex stretching)

Question 35

What is the traits and impact of the voltage gated K+ ion channels (what are they most known for playing a role in?)

Answer 35

it transmits electrical impulses along axons, more than 10 mill K+ ions pass per sec, and the channel is highly regulated with diff channels being controlled based on the voltage.

The channel is composed of 4 subunits and each unit has 6 transmembrane domains which sense voltage and open and close based on it