Membranes (mini-test) Flashcards
T/F: lipids form membranes
true
Membranes have ________ and _________
lipids, proteins
What classes of lipids are on/in membranes?
class 2, 3, and 4 (all besides class 1 which is triglycerides)
more specifically:
-phospholipids
-glycosphingolipids
-sphingolipids (and sphingomyelins)
-cholesterol (animal cells only)
What is the most abundant class in regards to membranes?
class 2- phospholipids
The polar head groups of membranes face outward and ____________ with water. Lipid fatty acid chains face inward and interact via ____________ interactions
hydrogen bond, hydrophobic
Where are glycolipids found on membrane? What is the general structure?
-glycolipids are the least common of all the membrane lipids
-they are always found in the outer leaflet of plasma membrane
-general structure has 2 parts:
1) 2 long hydrocarbon chains that are hydrophobic
2) carbohydrate component that is 1+ sugars and is hydrophilic
Where is cholesterol found on membrane?
both leaflets of the bilayer, but only in animal cells
Are there cholesterol esters on cell membrane?
no
cytoskeleton is an example of a __________
peripheral protein
What are the 2 types of membrane proteins?
1) integral (intrinsic) proteins
2) peripheral (extrinsic) proteins
Which membrane proteins can penetrate the phospholipid bilayer?
integral proteins
Can integral proteins be removed from membrane?
only if the membrane is disrupted
What are the 2 types of integral proteins?
1) single pass proteins like transporters
2) multi-pass, penetrates multiple spots of bilayer
Integral proteins are covalently linked to….
membrane phospholipids or glycolipids
Most integral proteins are __________
glycoproteins
What are the functions of the integral proteins?
receptors transport
Which membrane proteins do not penetrate membrane and are not covalently linked to any membrane components but are still associated with membrane?
peripheral proteins (note: they do form ionic links, NOT covalent)
Can peripheral proteins be removed from the membrane?
yes, can be dissociated from membrane by salt or pH
note: this will NOT disrupt the membrane integrity
T/F: peripheral proteins are located on both extracellular and intracellular sides of the membrane
true
What are the functions of peripheral proteins?
-enzyme activity
-signal transduction
-cytoskeletal proteins
Membranes are fluid not static, with the consistency of vegetable oil. The nature of lipids (_____________________) dictates fluidity and melting temp
length and degree of saturation
Do double bonds increase or decrease membrane fluidity?
increases fluidity
Does low temp increase or decrease membrane fluidity?
decreases fluidity
Does high temp increase or decrease membrane fluidity?
increases fluidity
How does cholesterol affect membrane fluidity in low temp?
cholesterol stabilizes cell membrane by not allowing close packing of FAs, which increases membrane fluidity
How does cholesterol affect membrane fluidity in high temp?
cholesterol has a melting temp of 298 degrees F, so because of this cholesterol can decrease the fluidity in high temp
Do saturated membranes have high or low melting temp?
high melting temp
(unsaturated= lower melting temp)
Do longer membranes have a high or low melting temp?
high melting temp
note:
-short chain FAs have lower melting temp
-also, longer chain decreases membrane fluidity
Do saturated membranes have more or less fluidity than unsaturated membranes?
less fluidity than unsaturated membranes
Cholesterol is a bulky rigid molecule that can change the fluidity of membranes. Cholesterol in membranes ___________ fluidity because it is rigid. Cholesterol prevents crystallization (making membrane solid) of FA side chains by fitting between them. Therefore, it __________ fluidity by disrupting the close packing of FA chains
decreases, increases
Lipids and proteins can move within membrane. How?
option 1: laterally switch from side to side
option 2: can flip with the help of flippase (but this is rare)
note: flippase helps establish phospholipid asymmetry
Are membranes symmetrical?
no
What is the main purpose of a membrane?
selective permeability
What are the 2 types of passive transport?
simple diffusion and facilitated diffusion
What is simple diffusion?
-goes from high to low conc.
-requires NO energy
-does not require transporter
-molecules that can simply diffuse/freely= water, oxygen, carbon dioxide, FAs, glycerol, 2-MG, etc
What is facilitated diffusion?
-goes from high to low conc.
-requires NO energy
-does require transporter
-ex: GLUT1 or GLUT2
What is active transport? What are the 2 types?
-goes against the conc gradient (from low to high conc.)
-faster than passive diffusion
-requires energy
-uses a transporter
2 types:
1) primary active transport
-uses ATP directly
-ex: sodium potassium pump
2) secondary active transport
-ATP is not seen, but energy is still being used
-ex: sodium glucose cotransporter (energy comes from the sodium)
What are the 3 types of transporters?
-uniport
-symport
-antiport
What is a uniport?
-facilitated diffusion transporter
-one molecule moves in one direction
-ex: GLUT1
What are the 2 cotransporters?
symport and antiport
What is a symport?
-its a cotransporter that moves 2 molecules in the same direction
-uses energy, so its active transport
-ex: sodium glucose cotransporter
What is an antiport?
-its a cotransporter that moves 2 molecules in opposite directions
-it uses energy, so its active transport
-ex: sodium potassium pump
What is the difference between endocytosis and exocytosis?
facilitated diffusion requires ____________
carrier proteins
T/F: facilitated diffusion occurs in either direction depending on conc. gradient
true
How is fructose transported through membrane?
GLUT5
T/F: eicosanoids are derived from membranes
true
What does eicosa mean?
20 (carbons)
Are eicosanoids essential?
no they’re synthesized as needed
Do eicosanoids come from cholesterol?
no
Where do ecosinoids come from?
FAs from phospholipids with 20 carbons
eicosanoids are derived from FAs that make up the cell membrane and nuclear membrane
Which molecules have FAs?
-triglyceride, diglyceride, monoglyceride
-phospholipid
-sphingolipid
-cholesterol ester
Eicosanoids are signaling molecules made by oxidation of 20 carbon _____________
poly-unsaturated fatty acids (which are either omega 3 or 6)
Are eicosanoids stored in cells?
NO
Which eicosanoids are inflammatory?
omega 6 eicosanoids
Which eicosanoids are anti-inflammatory?
omega 3 eicosanoids (cold water fish is best for this)
Which enzyme needs to be activated to make eicosanoids?
phospholipase A2
-it catalyzes an ester hydrolysis of phospholipid and cuts the 2nd FA attached to the glycerol, which frees a 20C FA
What are the precursors for eicosanoids?
-arachodonic acid which comes from linoleic acid
-eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA) which comes from alpha linolenic acid
so, arachodonic acid and EPA/DHA are the direct precursors
linoleic acid and alpha linolenic acid are the indirect precursors
Which FA is 20:4?
arachodonic acid
Is arachodonic acid an omega 3 or 6?
omega 6
arachodonic acid comes from….
linoleic acid
What food sources have EPA and DHA?
fish oil and baby formula
Which FA is 20:5?
EPA
Is EPA an omega 3 or 6?
omega 3
Which FA is 22:6?
DHA
Is DHA an omega 3 or 6?
omega 3
EPA/DHA comes from….
alpha linolenic acid
Eicosanoids are derived from either ______ or ________ FAs
omega 3, omega 6
All mammalian cells synthesize eicosanoids, expect….
RBC bc their cell membrane is vulnerable
Where do endocrine signaling molecules go?
to the blood
Eicosanoids act on the cells that produce them. This is called….
autocrine signaling (local signaling)
Eicosanoids act on neighboring cells. This is called…
paracrine signaling (local signaling)
What are 3 examples of eicosanoids?
-prostaglandins (PG)
-thromboxanes (TX)
-leukotrienes (LT)
Where do prostaglandins come from and what is their function?
-come from prostate gland and other tissues
-causes blood vessels to constrict and causes redness
Where do thromboxanes come from and what is their function?
come from platelets/thrombocytes and help blood clot
Where do leukotrienes come from and what is their function?
come from leukocytes and they secrete more cytokines during inflammatory response
If arachidonic acid comes in contact with lipoxygenases, what does it form?
omega 6 leukotreines
If arachidonic acid comes in contact with cyclooxygenases like COX1 and 2, what does it form?
omega 6 prostaglandin and thromboxane
If EPA/DHA comes in contact with lipoxygenases, what does it form?
omega 3 leukotrienes
If EPA/DHA comes in contact with cyclooxygenases like COX1 and 2, what does it form?
omega 3 prostaglandin and thromboxane
What do cyclooxygenases like COX1 and 2 do?
oxidizes FAs
Which medication is an irreversible inhibitor to COX1/2?
aspirin! It reduces synthesis of prostaglandin and thromboxane
Where does arachodonic acid usually reside?
C2 position of membrane phospholipids
What is the rate limiting enzyme in prostaglandin and thromboxane synthesis?
cyclooxygenase (COX)
