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Flashcards in Biological membranes Deck (49):

What are membrane functions

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


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



What is the hydrophobic and hydrophilic region of glycerophospholipid

diacylgycerol; phosphorylated alcohol


What is the hydrophobic and hydrophilic region of sphingomyelin

ceramide; phosphorylcholine


what is the hydrophobic and hydrophilic region of glycosphingolipid

ceramide; sugar residues


what is the hydrophobic and hydrophilic region of cholesterol

hydrocarbon rings; OH group at carbon 3


Inner and outer leaflets of single membranes have different compositions:

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


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

Phosphatidylserine; usually very little on outer leaflet, entirely internal


What does flipase do

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


What does amount of membrane movement depend on

percentage of unsaturated fatty acids


What does floppase do

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


What do scramblase's do

moves lipids in either direction, toward equilibrium


What physical factors affect fluidity of membrane

1. temperature
2. pressure
3. membrane potential


what chemical factors affect fluidity of membrane

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


what indirect factors affect fluidity of membrane

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


Unsaturated has more fluidity bc:

they cannot pack as tightly as saturated


% of saturated fats affects melting temp bc:

more long chain saturated fats inc melting temp due to packing


Lateral diffusion of cell-surface proteins is very fast:

1. virus induced fusion
2. mixture of labeled proteins from the membranes in heterokaryon (hybrid cell)


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

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.


What is the fluid mosaic model

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


what are the membrane proteins

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


What are amphitropic proteins

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


what is a glycophorin

a well characterized membrane protein of RBC's.
1. Hydrophobic domain
2. Hydrophillic domain (intracellular)
3. Membrane spanning (hydrophobic)


what are integral proteins

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


what are lipid rafts

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


What is a caveolin

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


what processes cause membrane fusion

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


what is exocytosis

membrane fusion and nuerotransmitter release


what proteins does exocytosis use

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.


what is endocytosis

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


What is receptor mediated endocytosis

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


What is familial hypercholesterolemia

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


What are the 2 types of active transport

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


Lipid bilayer is not a barrier for :

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


what can't cross lipid bilayer

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


What is solute movement across membranes like

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


Transporter reduces delta G of _____

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


What are the 6 major types of membrane transport

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:


What are general classes of transporters

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


what is the driving force in Simple diffusion



what is hypertonic

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


what is isotonic

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


what is hypotonic

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


What is a good ex of fasciliated diffusion

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


What are three types of Primary active transporters

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


How does Na/K+ ATPase work

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


What are ion channels

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.


How do voltage gated K+ channels work

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


what are ionophores

masks charge and shuttle ions across membrane.