Cell Membrane and Cell Polarity Flashcards Preview

BMS > Cell Membrane and Cell Polarity > Flashcards

Flashcards in Cell Membrane and Cell Polarity Deck (98):
1

Part of the plasma membrane which creates a barrier to most water soluble molecules

Lipids

2

Make up roughly 30% of the genome

Transmembrane proteins

3

The lipid and protein interactions in the plasma membrane are

Non-covalent

4

Proteins and lipids can often move in the

Bilayer

5

What are the four classes of membrane lipids?

1.) Phosphoglycerides
2.) Sphingolipids
3.) Glycolipids
4.) Sterols

6

Derived from 3-carbon glycerol backbone with 2 fatty acid chains attached to backbone

-There are three major types

Phosphoglycerides

7

Derived from sphingosine backbones

-Sphingomyelin is a major one

Sphingolipids

8

Often a sphingosene backbone with carbohydrates on the external face

Glycolipids

9

The four major classes of membrane lipids make up what percentage of the membrane mass?

50%

10

Their structure allows them to assemble into a bilayer which insulates the cell from the environment

Lipids

11

Amphipathic membrane lipids assemble spontaneously
into lipid bilayers and then into

Liposomes

12

Lipids in solution will first form a bilayer, with hydrophobic regions insulated from water, then free edges will associate to form a

Liposome

13

One chain lipids in solution will form

Micelles

14

What is the basic structure of a phosphoglyceride?

head group, then a phosphate, glycerol, and 2 hydrocarbon tails

15

Two fatty acid chains attach to two of the three carbons of the

Glycerol backbone

16

Importantly, one of the two chains is typically

-opposes dense packing and leads to membrane fluidity

Unsaturated (has a double bond)

17

The three major phospholipid groups of the plasma membrane are named according to their head groups. What are they?

1.) Phosphatidyl Ethanolamine
2.) Phosphatidyl Serine
3.) Phosphatidyl Choline

18

Has a net negative charge

Phosphatidyl Serine

19

What are the five major lipids of the plasma membrane?

1.) Phosphatidyl Ethanolamine
2.) Phosphatidyl Serine
3.) Phosphatidyl Choline
4.) Sphingomyelin
5.) Sphingosine

20

Stiffens regions of the plasma membrane in its vicinity

-found in both leaflets of plasma membrane

Cholesterol

21

Its aliphatic regions keep phospholipid chains apart

Cholesterol

22

How many types of glycolipids are there?

40 types

23

Charged glycolipids

Gangliosides

24

Derived from sphingosine but have sugars added rather than phosphate

Glyclipids

25

Asymmetric, meaning that their sugar is present only on the external face of the plasma membrane

Glycolipids

26

GM1 ganglioside is used for entry of

Cholera toxin

27

Lipid composition of specific membranes can vary by both membrane type and

Cell type

28

Primarily located in plasma membranes (less internal)

Cholesterol and sphingomeylin

29

Enriched in intracellular membranes such as in mitochondria or endoplasmic reticulum

Phosphatidylethanolamine and phosphatidylcholine

30

Located in the plasma membrane and enriched in meylin, but there are little in the internal membranes

Glycolipids

31

Lipids laterally diffuse in both inner and outer
layers but rarely

Flip between leaflets

32

Absent from bacteria and plants

Cholesterol

33

Subdomains of the plasma membrane that contain high concentrations of cholesterol and glycosphingolipids. They exist as distinct liquid-ordered regions of the membrane that are resistant to extraction with nonionic detergents

Lipid rafts

34

Plasma membrane lipids are asymmetrically distributed between

Internal and external faces

35

Which lipids typically make up the inner leaflet?

Phosphatidylethanolamine and phosphatidyl serine

36

Which lipids typically make up the outer leaflet?

Sphingolipids, glycolipids, and phosphotidylcholine

37

Areas of non-random lipid distribution within inner or outer membrane leaflet

Lipid Rafts

38

Lipids can non-randomly associate in "rafts" enriched in cholesterol and sphingomeylin. They can sequester subsets of

Membrane proteins

39

There are many thousands of

Minor lipids

40

An example of a "minor" lipid that is now known to have amajor role in signaling

Phosphotidylinositol (PI)

41

Phosphotidylinositol serves as a dock for downstream signaling molecules and is a precursor to soluble

IP3

42

Membrane proteins can be either

Integral or Peripheral

43

Incorporated into membrane with stretches of hydrophobic amino acids that are arranged in either alpha helices of 15-20 aa or barrels, with hydrophilic aa buried

Integral membrane proteins

44

Some "integral" proteins have a lipid covalently attached that can reversibly interact with the

-Are not true integral proteins

Membrane

45

Usually associate with the membrane through non-covalent interactions (like electrostatic interactions)

Peripheral membrane proteins

46

Serve as signaling molecule, adhesion, receptors, and transport

Membrane proteins

47

Proteins can be post-translationally bound to several types of lipids that then mediate association with the

Membrane

48

Membrane proteins can be immobilized by the underlying

Cytoskeleton

49

Membrane proteins often diffuse within the membrane
but can be anchored to

Cytoskeleton

50

Cytoskeletal protein spectrin is a dimer attached indirectly (via intermediates) to the transmembrane proteins

Glycophorin and/or band 3

51

Create a barrier to transport of many molecules, especially ions and small molecules

Membrane lipids

52

What are the three distinct types of molecules that serve as transporters across the membrane?

1.) Pumps
2.) Carriers
3.) Channels

53

Moves ions/molecules uphill, or against the gradient, and into or out of the cell

-highly specific

Pumps

54

Pumps require

Energy

55

Have an intermediate specificity and serve to help molecules/ions to move down their gradients (downhill) into/out of the cell

Carriers

56

Do carriers require energy input?

No

57

Not very specific and serve to allow molecules to freely flow down their gradients without physically helping them

Channels

58

Do channels require energy?

No

59

Of the three transporters, which is the only one that can transport multiple ions per conformational change?

Channel

60

Many disease states result from alterations in the levels or structure of

Transporters

61

Channels and carriers are considered to be

Passive transport

62

Ion-specific pores that open and close in a regulated manner

Channels

63

Enzyme-like proteins that mediate passive transport down concentration gradients without chemical change

Carriers

64

Enzymes that need energy to move ions and other solutes across the membrane against a concentration gradient; energy provided via ATP mediated phosphorylation or ATP binding and hydrolysis

Pumps

65

Can promote or oppose ion movements driven by concentration gradients

-combine to produce electrochemical gradient

Membrane potential

66

Regulation of pore opening (open/closed) alters ion flow and rejects inappropriate ion because of

Charge or Size

67

Which two things block sodium channels

Tetrodoxin and lidocaine

68

What are two potassium channel blockers?

Scorpion venum and cone snail toxins

69

What are the three major "carrier-type" transporters

Uniport, symport, and antiport

70

Carrier that allows passive transport down the concentration gradient

Uniport

71

Coupled transport where the transport of one solute depends on the transport of another

Symport (same direction) and Antiport (opposite directions)

72

In an antiport, the free energy release from a molecule moving down its concentration gradient can be used to

Drive the second transport step

73

Undergo a random switch between states that sequentially open on both membrane sides whether or not solute is bound

-The end result is that solutes will move down concentration gradient at higher rate than by diffusion

Uniport Carrier transporters

74

Carrier transporters will depend on concentration gradient and binding affinity similar to

Enzyme kinetics

75

What is an example of a coupled carrier transporter?

Na-Glucose symporter

76

Displays co-operative binding such that binding of Na+
increases affinity of symporter for glucose

Na-Glucose symporter

77

Allows transport of glucose against concentration gradient without direct energy expenditure

-both sites need to be occupied for conformational switch to occur

Na-Glucose symporter

78

Transcellular glucose transport from digestive system
through epithelial cell uses two

Glucose transporters

79

The first step in moving glucose through epithelial cells is that Na+ moves down its gradient which

Drags glucose inside (Na-Glucose symporter)

80

The second step in moving glucose through epithelial cells is that once inside the epithelial cell, glucose moves down its gradient through a

Different transporter

81

To keep the system working properly, epithelial cells get rid of the sodium brought in with glucose using a

-ATP dependent pump

Na/K transporter on basal surface

82

What are the three classes of ATP driven pumps?

1.) P-type
2.) F-type (and V-type)
3.) ABC transporter

83

Multi-pass TM domains that autophosphorylate themselves resulting in a conformational change that pumps ions

P-type pump

84

Has multiple subunits that uses H+ flux to drive ATP synthesis

-Also used to acidify vesicles

F-type (and V-type) pump

85

ATP-driven pump that pumps small molecules rather than ions

ABC transporter

86

One of the most important P-type transporters that keeps the Ca2+ concentration low in the cytosol

Ca2+ ATPase

87

Makes up 90% of membrane protein in muscle cells

Ca2+ ATPase

88

How does the Ca2+ TPase work?

Ca2+ binds non-phosphorylated transporter. This allows ATP to bind and phosphorylate the transporter which induces a conformational change that opens the channel to the lumen of the sarcoplasmic reticulum (SR) and releases Ca2+

89

Another important P-type phosphorylator that uses 1/3 of the cellular energy

Na/K ATPase

90

How does the Na/K ATPase work?

Na+ binds, phosphorylation induces conformational change that releases and allows K+ to bind. Dephosphorylation then induces another conformational change and K+ is released

91

What is the net movement of the Na/K ATPase?

Moves 3 Na+ out and 2 K+ in

92

Have two ATPase domains in each, and small molecules bind to the non-ATP bound state

-Abundant: can be 5% of genes in bacteria

ATP-binding-casettes (ABC transporters)

93

In an ABC transporter, when ATP is bound, the two ATPase domains dimerize, which produces a conformational change that

Exposes substrate to the opposite side of the membrane

94

ATP hydrolysis then releases the

Substrate

95

There are over 100 of these in humans and they are clinically important

ABC transporters

96

In multiple drug resistance (MDR), high levels of one type of ABC transporter can arise in tumor cells, which allows more hydrophobic drug to be cleared from cytoplasm so that

-occurs in 40% of cancers

Drug effects are reduced

97

ATP binding to cystic fibrosis TM conductance regulator protein (CFTR) drives opening and closing of a

Cl- channel (and ABC transporter)

98

Binds to acetylcholine receptor (Ach) and blocks nerve transmission

Curare

Decks in BMS Class (62):