Biological membranes

Question 1

What are membrane functions

Answer 1

1. barrier
2. cellular organization
3. transport
4. signal transduction
5. cell-cell communication

Question 2

membrane lipids are ____which mean they have a hydrophobic and hydrophilic component.

Answer 2

amphipathic

Question 3

What is the hydrophobic and hydrophilic region of glycerophospholipid

Answer 3

diacylgycerol; phosphorylated alcohol

Question 4

What is the hydrophobic and hydrophilic region of sphingomyelin

Answer 4

ceramide; phosphorylcholine

Question 5

what is the hydrophobic and hydrophilic region of glycosphingolipid

Answer 5

ceramide; sugar residues

Question 6

what is the hydrophobic and hydrophilic region of cholesterol

Answer 6

hydrocarbon rings; OH group at carbon 3

Question 7

Inner and outer leaflets of single membranes have different compositions:

Answer 7

One layer exposed to environment and one layer exposed to interior of cell.

Question 8

What gets flipped out to exterior of cell during apoptosis and serves as a signal for phagocytosis

Answer 8

Phosphatidylserine; usually very little on outer leaflet, entirely internal

Question 9

What does flipase do

Answer 9

move PE (phosphatidylehanolamine) and PS (phosphatylserine) from outer to cystolic leaflet

Question 10

What does amount of membrane movement depend on

Answer 10

percentage of unsaturated fatty acids

Question 11

What does floppase do

Answer 11

moves phospholipids from cystolic to outer leaflet (one used by phosphotidylserine)

Question 12

What do scramblase’s do

Answer 12

moves lipids in either direction, toward equilibrium

Question 13

What physical factors affect fluidity of membrane

Answer 13

1. temperature
2. pressure
3. membrane potential

Question 14

what chemical factors affect fluidity of membrane

Answer 14

1. head group of phospholipid
2. FA chain length
3. FA unsaturation
4. cholesterol

Question 15

what indirect factors affect fluidity of membrane

Answer 15

1. hormones
2. adaptation to stress
3. cell cycle
4. cell differentiation

Question 16

Unsaturated has more fluidity bc:

Answer 16

they cannot pack as tightly as saturated

Question 17

% of saturated fats affects melting temp bc:

Answer 17

more long chain saturated fats inc melting temp due to packing

Question 18

Lateral diffusion of cell-surface proteins is very fast:

Answer 18

1. virus induced fusion

2. mixture of labeled proteins from the membranes in heterokaryon (hybrid cell)

Question 19

Flourescence recovery after photobleaching is a techniqe to monitor lateral diffusion of lipids and proteins in membranes. How does it work?

Answer 19

1. Shine light on it –> bleaches out flourescence
2. Fourescence intensity goes very down
3. Wait and it starts to recover as other still labeled monomers come to that region
   - This shows that there is a lot of movement within our membranes.

Question 20

What is the fluid mosaic model

Answer 20

lipid bilayer composed of phospholipids and sphingolipids. There are peripheral proteins, integral proteins, glycolipids

Question 21

what are the membrane proteins

Answer 21

1. peripheral
2. amphitropic
3. integral
4. lipid (GPI) -linked

Question 22

What are amphitropic proteins

Answer 22

proteins that bind loosely to suruface of lipid bilayer and can be released.

Question 23

what is a glycophorin

Answer 23

a well characterized membrane protein of RBC’s.

1. Hydrophobic domain
2. Hydrophillic domain (intracellular)
3. Membrane spanning (hydrophobic)

Question 24

what are integral proteins

Answer 24

All have an alpha helical, hydrophobic region of aa that will be the membrane spanning portion.

Question 25

what are lipid rafts

Answer 25

stable microdomains of cholesterol and sphingolipids that can form on either the inner or outer leaflet that serve as sites for lipid -linked protein attachment

Question 26

What is a caveolin

Answer 26

protein dimers that are lipid-linked to the cell membrane, they produce invaginations in the cell membrane

Question 27

what processes cause membrane fusion

Answer 27

1. building of vesicles from golgi complexes 2. exocytosis 3. endocytosis 4. viral infection 5. fusion of sperm and egg

Question 28

what is exocytosis

Answer 28

membrane fusion and nuerotransmitter release

Question 29

what proteins does exocytosis use

Answer 29

SNARE's and SNAP25; form zipped up component and keeps pulling it toward fusion until you get an opening for contents of vesicles to be released.

Question 30

what is endocytosis

Answer 30

1. phagocytosis of particulate matter 2. pinocytosis take up extracellular fluid 3. receptor mediated endocytosis

Question 31

What is receptor mediated endocytosis

Answer 31

LDL receptors bind to LDL particles that cause them to be endocytosed.

Question 32

What is familial hypercholesterolemia

Answer 32

People who have defective LDL receptors accumulate high levels of LDL in their blood that cause them to have heart attacks and atherosclerasis

Question 33

What are the 2 types of active transport

Answer 33

1. Primary active transport: Directly use ATP hydrolysis to move things in and out 2. Secondary active transport: Use ATP hydrolysis to create a conc. gradient that is used to symport other things in and out

Question 34

Lipid bilayer is not a barrier for :

Answer 34

1. gases (oxygen, CO2) 2. ethanol (polar molecules and small uncharged) 3. water

Question 35

what can't cross lipid bilayer

Answer 35

1. large molecules - glucose 2. ions 3. polar charged molecules - aa, nucleotides, sugar phosphates

Question 36

What is solute movement across membranes like

Answer 36

movement of charged solutes will depend on a combination of chemical and electrical gradients: electrochemical potential

Question 37

Transporter reduces delta G of _____

Answer 37

diffusion; makes it more efficient to get it in and out

Question 38

What are the 6 major types of membrane transport

Answer 38

1. Simple diffusion: nonpolar compounds only, down conc gradient (high to low) 2. Fascilitated diffusion: uses protein; from high to low 3. Primary active transport: against electrochemical gradient 4. Secondary active transport: 5. ion channels: 6. ionophores:

Question 39

What are general classes of transporters

Answer 39

1. uniporters: carry 1 molecule back and forth 2. symporter: take 2 molecules in same direction 3. antiport: taking one in and one out at the same time

Question 40

what is the driving force in Simple diffusion

Answer 40

entropy

Question 41

what is hypertonic

Answer 41

high salt solution than intracellularly so water diffuses out and cell shrivels

Question 42

what is isotonic

Answer 42

salt conc is same inside and out. cell is in equilibrium

Question 43

what is hypotonic

Answer 43

higher salt conc inside than outside, so water goes inside cell to make equal conc. cells swell

Question 44

What is a good ex of fasciliated diffusion

Answer 44

1. chloride bicarbonate exchanger. it uses an antiporter | 2. GLUT1 Transporter

Question 45

What are three types of Primary active transporters

Answer 45

1. P type: Na/K ATPase, SERCA calcium pumps 2. F type: uses proton gradient; ex is mitochondrial ATP synthase 3. ABC Type: dimer with 2 ATPase. Ex: CFTR

Question 46

How does Na/K+ ATPase work

Answer 46

Sets up membrane potential. Makes it more negative on the inside and more positive on outside. Ships 3 Na out and 2 K+ in. Low sodium inside, high potassium

Question 47

What are ion channels

Answer 47

1. Resting is always open 2. Voltage gated: responds to change in membrane potential 3. Ligand gated: responds to extracellular neurotransmitter 4. signal gated: responds to int cellular signal transduction events.

Question 48

How do voltage gated K+ channels work

Answer 48

Contain R residues that are pulled toward - charged cytosol. When membrane depolarizes, pull is lessened, conformation changes, pore opens.

Question 49

what are ionophores

Answer 49

masks charge and shuttle ions across membrane.