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Biochemistry 1 > Membranes (mini-test) > Flashcards

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
Q

How does cholesterol affect membrane fluidity in low temp?

A

cholesterol stabilizes cell membrane by not allowing close packing of FAs, which increases membrane fluidity

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26
Q

How does cholesterol affect membrane fluidity in high temp?

A

cholesterol has a melting temp of 298 degrees F, so because of this cholesterol can decrease the fluidity in high temp

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27
Q

Do saturated membranes have high or low melting temp?

A

high melting temp

(unsaturated= lower melting temp)

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28
Q

Do longer membranes have a high or low melting temp?

A

high melting temp

note:
-short chain FAs have lower melting temp
-also, longer chain decreases membrane fluidity

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29
Q

Do saturated membranes have more or less fluidity than unsaturated membranes?

A

less fluidity than unsaturated membranes

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30
Q

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

A

decreases, increases

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31
Q

Lipids and proteins can move within membrane. How?

A

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

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32
Q

Are membranes symmetrical?

A

no

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33
Q

What is the main purpose of a membrane?

A

selective permeability

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34
Q

What are the 2 types of passive transport?

A

simple diffusion and facilitated diffusion

35
Q

What is simple diffusion?

A

-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
Q

What is facilitated diffusion?

A

-goes from high to low conc.
-requires NO energy
-does require transporter
-ex: GLUT1 or GLUT2

37
Q

What is active transport? What are the 2 types?

A

-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
Q

What are the 3 types of transporters?

A

-uniport
-symport
-antiport

39
Q

What is a uniport?

A

-facilitated diffusion transporter
-one molecule moves in one direction
-ex: GLUT1

40
Q

What are the 2 cotransporters?

A

symport and antiport

41
Q

What is a symport?

A

-its a cotransporter that moves 2 molecules in the same direction
-uses energy, so its active transport
-ex: sodium glucose cotransporter

42
Q

What is an antiport?

A

-its a cotransporter that moves 2 molecules in opposite directions
-it uses energy, so its active transport
-ex: sodium potassium pump

43
Q

What is the difference between endocytosis and exocytosis?

A
44
Q

facilitated diffusion requires ____________

A

carrier proteins

45
Q

T/F: facilitated diffusion occurs in either direction depending on conc. gradient

A

true

46
Q

How is fructose transported through membrane?

A

GLUT5

47
Q

T/F: eicosanoids are derived from membranes

A

true

48
Q

What does eicosa mean?

A

20 (carbons)

49
Q

Are eicosanoids essential?

A

no they’re synthesized as needed

50
Q

Do eicosanoids come from cholesterol?

A

no

51
Q

Where do ecosinoids come from?

A

FAs from phospholipids with 20 carbons

eicosanoids are derived from FAs that make up the cell membrane and nuclear membrane

52
Q

Which molecules have FAs?

A

-triglyceride, diglyceride, monoglyceride
-phospholipid
-sphingolipid
-cholesterol ester

53
Q

Eicosanoids are signaling molecules made by oxidation of 20 carbon _____________

A

poly-unsaturated fatty acids (which are either omega 3 or 6)

54
Q

Are eicosanoids stored in cells?

A

NO

55
Q

Which eicosanoids are inflammatory?

A

omega 6 eicosanoids

56
Q

Which eicosanoids are anti-inflammatory?

A

omega 3 eicosanoids (cold water fish is best for this)

57
Q

Which enzyme needs to be activated to make eicosanoids?

A

phospholipase A2
-it catalyzes an ester hydrolysis of phospholipid and cuts the 2nd FA attached to the glycerol, which frees a 20C FA

58
Q

What are the precursors for eicosanoids?

A

-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
Q

Which FA is 20:4?

A

arachodonic acid

60
Q

Is arachodonic acid an omega 3 or 6?

A

omega 6

61
Q

arachodonic acid comes from….

A

linoleic acid

62
Q

What food sources have EPA and DHA?

A

fish oil and baby formula

63
Q

Which FA is 20:5?

A

EPA

64
Q

Is EPA an omega 3 or 6?

A

omega 3

65
Q

Which FA is 22:6?

A

DHA

66
Q

Is DHA an omega 3 or 6?

A

omega 3

67
Q

EPA/DHA comes from….

A

alpha linolenic acid

68
Q

Eicosanoids are derived from either ______ or ________ FAs

A

omega 3, omega 6

69
Q

All mammalian cells synthesize eicosanoids, expect….

A

RBC bc their cell membrane is vulnerable

70
Q

Where do endocrine signaling molecules go?

A

to the blood

71
Q

Eicosanoids act on the cells that produce them. This is called….

A

autocrine signaling (local signaling)

72
Q

Eicosanoids act on neighboring cells. This is called…

A

paracrine signaling (local signaling)

73
Q

What are 3 examples of eicosanoids?

A

-prostaglandins (PG)
-thromboxanes (TX)
-leukotrienes (LT)

74
Q

Where do prostaglandins come from and what is their function?

A

-come from prostate gland and other tissues
-causes blood vessels to constrict and causes redness

75
Q

Where do thromboxanes come from and what is their function?

A

come from platelets/thrombocytes and help blood clot

76
Q

Where do leukotrienes come from and what is their function?

A

come from leukocytes and they secrete more cytokines during inflammatory response

77
Q

If arachidonic acid comes in contact with lipoxygenases, what does it form?

A

omega 6 leukotreines

78
Q

If arachidonic acid comes in contact with cyclooxygenases like COX1 and 2, what does it form?

A

omega 6 prostaglandin and thromboxane

78
Q

If EPA/DHA comes in contact with lipoxygenases, what does it form?

A

omega 3 leukotrienes

79
Q

If EPA/DHA comes in contact with cyclooxygenases like COX1 and 2, what does it form?

A

omega 3 prostaglandin and thromboxane

80
Q

What do cyclooxygenases like COX1 and 2 do?

A

oxidizes FAs

81
Q

Which medication is an irreversible inhibitor to COX1/2?

A

aspirin! It reduces synthesis of prostaglandin and thromboxane

82
Q

Where does arachodonic acid usually reside?

A

C2 position of membrane phospholipids

83
Q

What is the rate limiting enzyme in prostaglandin and thromboxane synthesis?

A

cyclooxygenase (COX)

Biochemistry 1 (12 decks)

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