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Membranes (mini-test) Flashcards

1
Q

T/F: lipids form membranes

A

true

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2
Q

Membranes have ________ and _________

A

lipids, proteins

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3
Q

What classes of lipids are on/in membranes?

A

class 2, 3, and 4 (all besides class 1 which is triglycerides)

more specifically:
-phospholipids
-glycosphingolipids
-sphingolipids (and sphingomyelins)
-cholesterol (animal cells only)

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4
Q

What is the most abundant class in regards to membranes?

A

class 2- phospholipids

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5
Q

The polar head groups of membranes face outward and ____________ with water. Lipid fatty acid chains face inward and interact via ____________ interactions

A

hydrogen bond, hydrophobic

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6
Q

Where are glycolipids found on membrane? What is the general structure?

A

-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

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7
Q

Where is cholesterol found on membrane?

A

both leaflets of the bilayer, but only in animal cells

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8
Q

Are there cholesterol esters on cell membrane?

A

no

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9
Q

cytoskeleton is an example of a __________

A

peripheral protein

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10
Q

What are the 2 types of membrane proteins?

A

1) integral (intrinsic) proteins
2) peripheral (extrinsic) proteins

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11
Q

Which membrane proteins can penetrate the phospholipid bilayer?

A

integral proteins

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12
Q

Can integral proteins be removed from membrane?

A

only if the membrane is disrupted

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13
Q

What are the 2 types of integral proteins?

A

1) single pass proteins like transporters
2) multi-pass, penetrates multiple spots of bilayer

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14
Q

Integral proteins are covalently linked to….

A

membrane phospholipids or glycolipids

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15
Q

Most integral proteins are __________

A

glycoproteins

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16
Q

What are the functions of the integral proteins?

A

receptors transport

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17
Q

Which membrane proteins do not penetrate membrane and are not covalently linked to any membrane components but are still associated with membrane?

A

peripheral proteins (note: they do form ionic links, NOT covalent)

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18
Q

Can peripheral proteins be removed from the membrane?

A

yes, can be dissociated from membrane by salt or pH

note: this will NOT disrupt the membrane integrity

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19
Q

T/F: peripheral proteins are located on both extracellular and intracellular sides of the membrane

A

true

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20
Q

What are the functions of peripheral proteins?

A

-enzyme activity
-signal transduction
-cytoskeletal proteins

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21
Q

Membranes are fluid not static, with the consistency of vegetable oil. The nature of lipids (_____________________) dictates fluidity and melting temp

A

length and degree of saturation

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22
Q

Do double bonds increase or decrease membrane fluidity?

A

increases fluidity

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23
Q

Does low temp increase or decrease membrane fluidity?

A

decreases fluidity

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24
Q

Does high temp increase or decrease membrane fluidity?

A

increases fluidity

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25
How does cholesterol affect membrane fluidity in low temp?
cholesterol stabilizes cell membrane by not allowing close packing of FAs, which increases membrane fluidity
26
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
27
Do saturated membranes have high or low melting temp?
high melting temp (unsaturated= lower melting temp)
28
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
29
Do saturated membranes have more or less fluidity than unsaturated membranes?
less fluidity than unsaturated membranes
30
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
31
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
32
Are membranes symmetrical?
no
33
What is the main purpose of a membrane?
selective permeability
34
What are the 2 types of passive transport?
simple diffusion and facilitated diffusion
35
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
36
What is facilitated diffusion?
-goes from high to low conc. -requires NO energy -does require transporter -ex: GLUT1 or GLUT2
37
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)
38
What are the 3 types of transporters?
-uniport -symport -antiport
39
What is a uniport?
-facilitated diffusion transporter -one molecule moves in one direction -ex: GLUT1
40
What are the 2 cotransporters?
symport and antiport
41
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
42
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
43
What is the difference between endocytosis and exocytosis?
44
facilitated diffusion requires ____________
carrier proteins
45
T/F: facilitated diffusion occurs in either direction depending on conc. gradient
true
46
How is fructose transported through membrane?
GLUT5
47
T/F: eicosanoids are derived from membranes
true
48
What does eicosa mean?
20 (carbons)
49
Are eicosanoids essential?
no they're synthesized as needed
50
Do eicosanoids come from cholesterol?
no
51
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
52
Which molecules have FAs?
-triglyceride, diglyceride, monoglyceride -phospholipid -sphingolipid -cholesterol ester
53
Eicosanoids are signaling molecules made by oxidation of 20 carbon _____________
poly-unsaturated fatty acids (which are either omega 3 or 6)
54
Are eicosanoids stored in cells?
NO
55
Which eicosanoids are inflammatory?
omega 6 eicosanoids
56
Which eicosanoids are anti-inflammatory?
omega 3 eicosanoids (cold water fish is best for this)
57
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
58
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
59
Which FA is 20:4?
arachodonic acid
60
Is arachodonic acid an omega 3 or 6?
omega 6
61
arachodonic acid comes from....
linoleic acid
62
What food sources have EPA and DHA?
fish oil and baby formula
63
Which FA is 20:5?
EPA
64
Is EPA an omega 3 or 6?
omega 3
65
Which FA is 22:6?
DHA
66
Is DHA an omega 3 or 6?
omega 3
67
EPA/DHA comes from....
alpha linolenic acid
68
Eicosanoids are derived from either ______ or ________ FAs
omega 3, omega 6
69
All mammalian cells synthesize eicosanoids, expect....
RBC bc their cell membrane is vulnerable
70
Where do endocrine signaling molecules go?
to the blood
71
Eicosanoids act on the cells that produce them. This is called....
autocrine signaling (local signaling)
72
Eicosanoids act on neighboring cells. This is called...
paracrine signaling (local signaling)
73
What are 3 examples of eicosanoids?
-prostaglandins (PG) -thromboxanes (TX) -leukotrienes (LT)
74
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
75
Where do thromboxanes come from and what is their function?
come from platelets/thrombocytes and help blood clot
76
Where do leukotrienes come from and what is their function?
come from leukocytes and they secrete more cytokines during inflammatory response
77
If arachidonic acid comes in contact with lipoxygenases, what does it form?
omega 6 leukotreines
78
If arachidonic acid comes in contact with cyclooxygenases like COX1 and 2, what does it form?
omega 6 prostaglandin and thromboxane
78
If EPA/DHA comes in contact with lipoxygenases, what does it form?
omega 3 leukotrienes
79
If EPA/DHA comes in contact with cyclooxygenases like COX1 and 2, what does it form?
omega 3 prostaglandin and thromboxane
80
What do cyclooxygenases like COX1 and 2 do?
oxidizes FAs
81
Which medication is an irreversible inhibitor to COX1/2?
aspirin! It reduces synthesis of prostaglandin and thromboxane
82
Where does arachodonic acid usually reside?
C2 position of membrane phospholipids
83
What is the rate limiting enzyme in prostaglandin and thromboxane synthesis?
cyclooxygenase (COX)

Biochemistry 1 (12 decks)

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