Chapter 11 Membranes Flashcards
What kind of structure is the biological membrane?
sheet like, few molecules thick, and self sealing
What does the biological membrane contain?
Contain amphipathic lipids, proteins and carbohydrates. Non-covalent Interactions (van deer walls which attract the nonpolar tails together)
_______ carry out most of the specific functions on the biological membrane.
Proteins
What are the membrane proteins functions contain?
receptors, enzymes, ion channels, calcium pumps
What are the carbohydrates on the membrane important for?
(attached to lipids = glycolipids, or to
proteins = glycoproteins) - important in communication/recognition
This is also the function of the post-translational modification (review assignment sheet)
What is the hydrophobic effect?
major driving force of the lipid bilayer
for example: mixing lipids and oils into water
______ and _______ form a lipid bilayer.
phospholipids and glycolipids
Membranes are _______ in that the outer surface is always different from the inner surface.
asymmetric (asymmetric arrangement)
Is the biological membrane polarized or unpolarized?
polarized: inside is negative (-60mV). Plays a role in transport, energy conversion and excitability.
- -Inside of axon is (-) and the ECF is (+)
What are the two types of diffusion in lipids?
Lateral and Transverse diffusion
Define lateral diffusion
rapid change of solid to liquid state
Define transverse (flip-flopping) diffusion
very slow (rare) change of solid to liquid state
How did they proof lateral diffusion existed?
They let bleach sit on a sample with lots of lipids and did a fluorescent recovery (FRAP) and found there was movement b/w lipids
What is the The Fluid Mosaic Model?
it describes the lipid bilayer of vesicles as a dynamic, liquid-like environment that allows the free motion of non-polar molecules throughout its structure.
(Proposed by Singer and Nicolson in 1972)
What are liposomes?
they are aqueous compartments enclosed by a lipid bilayer
What are the function of liposomes (lipid vesicles)?
they deliver chemicals/drugs/DNA to specific tissues
What is so special about liposomes?
They have an inner and outer aqueous compartment which helps in delivering chemicals to tissues. The aqueous compartments are enclosed by a lipid membrane
What is the function of the homing peptides on the outside of liposomes?
they help target what organ to go to
_____ have a harder time getting through the membrane when attached to H2O. They have to release the H2O as they go through the ______ to get through the membranes.
Charged ions (Na, K, Cl) channels
H2O is special when going through membranes because it goes through by ________.
simple diffusion
When you have saturated fatty acids, more viscous (tightly packed), does the fluidity increase or decrease?
Decrease
When you have unsaturated (kinked) fatty acids, does the fluidity increase or decrease?
Increase
In saturated fatty acids (no double bonds), what does the melting temp and fluidity do? Increase or decrease?
Melting temp INC
Fluidity DEC
In unsaturated fatty acids (double bonds present), what does the melting temp and fluidity do? Increase or decrease?
Melting temp DEC
Fluidity INC
Solid like means long chain fatty acids OR short chain fatty acids and saturated OR unsaturated fatty acids?
long chains of fatty acids
saturated (more compact)
Fluid like means long chain fatty acids OR short chain fatty acids and saturated OR unsaturated fatty acids?
short chains of fatty acids
unsaturated (less compact)
What are the 4 factors that determine solid like and fluid like?
Temperature, chain length, saturation vs. unsaturated, cholestrol
As the temperature increases, is that solid like or fluid like?
fluid like
As the temperature decreases, is that solid like or fluid like?
solid like
Longer chain of carbons, then its more compact, which means more ______ like.
solid
Unsaturated fatty acid means more kinks, which ______ fluidity
increase
__________ disrupts the tight packing of the fatty acid chains, therefore it is more ______ like.
Cholesterol, fluid
While membrane _______ establish a permeability barrier, membrane ______ allow transport of molecules and information across the membrane.
lipids
proteins
the more proteins, the MORE ______ are being transferred
molecules and ions
Integral Membrane Protein is embedded where?
in the membrane
Peripheral Membrane Protein is located where?
NOT embedded in the membrane, attached to extracellular surface
How are peripheral proteins attached to the surfaces of membranes (EC surfaces)?
Through being bound to head groups of lipids by electrostatic and hydrogen-bond, bound to integral membrane protein, or post-translationally modified to contain a fatty acid chain.
For one example of a peripheral membrane protein, the polimitate attaches to the ______ in the membrane.
cytseine
In an integral membrane protein, what would be the properties of the amino acids in the protein?
most of them are hydrophobic amino acids because they are embedded in the membranes away from the ECF
in porin, there is a barrel that allows the entry of charged ions and it has _______ amino acids on the inside
hydrophilic
Any protein that gets halfway or a quarter of the way through a membrane is classified as a _________
Intergral membrane protein
In the formation of prostaglandin H2 from arachidonate by prostaglandin H2 synthase, how many steps are needed for the final product?
2
____________ +___________ =
Prostaglandin H2 synthase
Cyclooxygenase + Peroxidase
What does the formation of prostaglandin H2 do?
Promotes inflammation & modulates gastric acid secretion. It produces fever.
How does ASA work?
-Aspirin inhibits cyclooxygenase activity by obstructing the channel which causes a conformational change with the protein and the arachidonic cant bind
What is the criteria for a molecule being able to pass through a membrane through simple diffusion?
- The concentration of the molecule is higher on one side of the membrane than the other.
- The molecule is lipophilic or soluble in nonpolar solutions.
Polar molecules can diffuse across a membrane down their concentration gradient only with the assistance of a particular protein called a channel. Such movement is called ______ or _______.
facilitated diffusion or passive transport
Movement of molecules against a concentration gradient requires a source of energy and is called________.
Active tranport
What are the factors that determine simple diffusion across a membrane?
no assistance needed and molecules that dissolve in lipid.
Ex: Lipophilic molecule such as steroid
What are the factors that determine Passive Transport/Facilitated Diffusion across a membrane?
-Rate of diffusion enhanced by carrier or channel (integral
membrane protein) and Rapid diffusion “down a concentration gradient
-Energy comes from the molecule itself
EX: sodium ions
What are the two types of active transport?
Primary and secondary
What is primary active transport?
transport of solute against its concentration gradient, where ATP required
What is secondary active transport?
ATP required; flow of one molecule promotes flow of another molecule (Antiporters vs symporters)
As the solute increases, the rate of transport ______
Increases
Functions of the Na+-K+ Pump (Na+-K+ ATPase)
- Controls cell volume
- Promotes electrical excitability
- Drives transport of sugars and Amino acids
What does Na+-K+ Pump pump? and where is the ATP located to drive the pump?
Pumps 3 Na+ out & 2 K+ into cell. ATP inside to drive the pump
Why are channels called P-type ATPases?
because the channel is phosphorylated and changes conformation
Examples of primary active transport
Na+-K+ ATPase
Ca2+ ATPase
H+-K+ pump
Examples of secondary active transport
Na+ -glucose symporter
Na+- Ca2+ Exchanger
In order for secondary active transport to work, it has to be what?
Coupled with a primary active transport
What is an antiporter secondary transport system?
the two substrates flow in opposite directions (ex: Na+ Ca+ channel)
What is a symporter secondary transport system?
the two substrates flow in the same direction (ex: Na+ glucose channel)
What are the 3 voltage gated cahnnels?
Na, K, and Ca
How does the selectivity filter work?
-Ion path begins (on inner surface) as wide, water-filled channel, so cations can enter with hydration sphere intact.
Partway through membrane, channel narrows, so waters of hydration have to come off.
-Carbonyl O atoms from protein backbone in selectivity filter region replace water molecules, binding to K+, with a series of perfect coordination shells through which K+ can move.
-Na+ ions can’t interact favorably with the filter (they’re too small) and they don’t release the water as easily as K+.
What is Digitalis’s function?
inhibits the Na+-K+ pump
- increases Na+ inside of the heart and decreases K+ in the heart.
- increase in intracellular Na+ slows down the expulsion of Ca2+.
- increase in Ca2+ enhances contraction of the heart
Digitalis information
in heart disease the patients need the Ca+ in the cells so the digitalis is a drug that blocks the Na+ K+ pathway so more na+ is on the inside which then blocks the secondary AT and more Ca+ is stored on the inside
—The INC of Ca+ enhances the contraction of the heart
MultiDrug-Resistance (MDR) Proteins or
P-glycoprotein are over expressed in what?
tumors, drugs like chemo cant enter the cell because the cell uses the ATP to spit the drug out
- This is because the tumors build a resistance to the drugs
- 4 domains: 2 membrane spanning domain and 2 ATP-binding domain (ATP-binding cassettes-ABC).
- ABC transporters
Where is the defect in this disease Harlequin Ichthyosis?
defect in ABC transporter for lipids in keratinocytes
