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Flashcards in Exam 2 Deck (135):
1

What are a couple of tools cells use for movement?

Shape change
Flagella

2

What is meant by "dynamic" when we talk about the membrane

It has complex patterns of internal movement and organelles move within it.

3

What are the major lipid bilayer components

Amphipatic lipids
Proteins
Carbohydrates

4

How much of membrane does each component make up?

Phospholipids - 50 to 90%
Sterols - 2-25%
Glycolipids - less than 5%
Proteins -20 to 80%
Carbohydrates - none. They are outside membrane.

5

What are the four polar heads of major lipids? Which one is charged?

Phosphatidylethanolamine
Phosphatidyl serine - charged
Phosphatidyl choline
Sphingomyelin - a sphingosine derivative

6

Is there an example to the exception to the lipid bilayer?

Lipid mono layers are seen in archea, extremophiles. Made up of bipolar molecules with a fatty acid in the middle. Laid next to each other vertically with polar side on each end.

7

What force drives the shape of the lipid bilayer?

Hydrophobic forces
Van der waals forces

8

What lipid is only found in eukaryotes?

Sterols

9

What is the function of lipids and carbs in the lipid bilayer?

Help protect plasma membrane
Cell to cell signaling

10

How can one change the fluidity of a membrane?

Change fatty acid length
Change fatty acid saturation/desaturation

11

How is a membranes fluidity helpful?

Allows cells to fit surroundings
Prevents membrane from becoming leaky

12

How can we chemically control a membranes fluidity

Fatty acyl desaturated help lipids become desaturated. Fatty acid reductases help fatty ticks become more saturated.

13

What are phospholipids made of

Glycerol, two fatty acids with a polar head

14

Are both fatty acids saturated in a phospholipid?

No. One is saturated. The other is unsaturated.

15

What phospholipid is important in signaling

Phosphatidyl inositol

16

Why do hydrophobic forces roll lipid into ball

More energetically favorable

17

How do we use synthetic vesicles

We use these liposomes for drug delivery. Sometimes used in aerosols. Liposomes are then endocytosed.

18

What is the structure of a sterol?

Four rigid rings, single polar hydroxyl group, short nonpolar hydrocarbon chain

19

What is the function of a sterol

Controls membrane fluidity. Cholesterol. Stick in between phospholipids in bilayer

20

What is attached to lipid in glycolipids

Sugars

21

What kind of fluid is the lipid bilayer

Two dimensional

22

What can change fluidity of lipid bilayer?

Temperature
Chemical composition

23

If something is fluid at a low temperature, is it saturated or desaturated?

It is less saturated

24

How does organism adjust to temperature change?

Change fluidity of membrane
Control total cholesterol

25

How does one change fluidity of membrane?

Use desaturated to desaturated the membranes in order to get more fluidity

26

Which bacteria I'll be the most fluid at low temps

Those with shorter tails

27

What happens to fluidity if cholesterol increases?

It decreases

28

What kind of bond exists phospholipid and cholesterol on lipid membrane

Hydrogen bond

29

What technique is used to measure membrane fluidity

Fluorescence recovery after photo bleaching

30

three steps of FRAP

1. Label membrane with fluorophore
2. Bleach label with laser in small area of cell. Destroy label, not membrane,
3. Monitor recovery of signal. This will show how quickly diffusion happens.

31

Why are lipid bilayers asymmetrical?

Leaflets are different, have different chemical compositions

32

Why are lipid bilayers asymmetrical

So cell knows which way is up and down

33

How is membrane generated and maintained

1-new membrane made in ER
2-proteins inserted in lipid bilayer with specific orientation
3-glycolipids and glycoproteins are made/modified in Golgi apparatus

34

What are flip passes in ER

Transfer p-lipid from Cytosolic side to external side of bilayer

35

How is new membrane sent out of ER

Vesicles

36

What happens if a protein is inserted backwards

It may not work

37

In Golgi, what do sugars never face?

The cytosol

38

Four purposes of proteins

Transporters
Anchors
Receptors
Enzymes

39

Two types of membrane proteins

Peripheral
Integral

40

Peripheral protein

Loosely associated
Noncovalent interaction with integral protein or lipid

41

Integral protein

Transmembrane domain containing protein - usually has one or more hydrophobic or amphipatic alpha helix or beta barrels
Lipid linked protein

42

What is orientation of alpha helix? How many subunits doe it have?

Vertical
One

43

Multi pass

More than one subunit threading through PM, and will have both hydrophobic and hydrophilic parts. Side chains are hydrophobic. Are often transporters.

44

Beta barrels

Form huge holes in membrane. Are always open. Undergo no conformation change.

45

Porins

Beta barrels. Found outside mitochondria and chloroplasts. Static. No large scale conformation change.

46

Lipid linked protein

Post translational modifications
Palmitoylation
Prenylation
Protein is anchored to bilayer even though amino acids do interact
Lipid linkages allow for fast diffusion

47

Palmitoylation

Covalent attachment of fatty acid

48

Prenylation

Addition of hydrophobic molecule to protein or chemical compound

49

How does one study integral membrane proteins

Add detergent to solubilize protein (SDS, triton, etc.)
Purify
Slowly add back
Phospholipids-->liposome-->study

50

SDS

Strong a ionic detergents

51

Why difficult to study integral protein

Nonpolar
Highly insoluble, hard to purify, hard to study

52

Book method to study integral proteins

1. Integral membrane protein in sample
2. Add detergent micelles and monomers
3. Solubilize membrane proteins
4. Add lipid-detergent micelles
5. Purify protein
6. Add phospholipids to remove detergent
7. Protein incorporated into phospholipid vesicle

53

Oleate

Fatty acid with one kink

54

Stearate

Saturated fatty acid

55

What are cell solutions for having a weak lipid bilayer?

Cell cortex
Glycocalyx
Cell walls
Tight junctions

56

Cell cortex

Inside plasma membrane
A network of mesh like proteins
Spectrin, actin linked to transmembrane anchor proteins (reinforce)

57

Glycocalyx

Carb layer
On outside of PM
Protective layer in animal cells
Like a loose cell wall
Importsnt for cell cell attachment

58

Where do we find cell walls

Fungi, plants, bacteria

59

How do neutrophils slow down in veins

Lectins recognize their carb layers, bind to them, and slow them down so they can exit veins

60

What would happen if there were no tight junctions

Proteins would end up on any side of the cell

61

Why is fluid mosaic model flawed

Cells in tissues have domains on plasma membranes. Protein movement is restricted to specific sides of cells

62

What does cell polarity mean

They have a top, bottom,left, right, front and back

63

How is protein movement restricted (3)

Cell cortex
Extracellular matrix
Proteins on adjacent cells

64

Apical vs basolateral

Apical faces lumen. Basolateral is bottom

65

How so do we track protein movement

Fluorescence

66

What are micro domains

Lipid rafts

67

What are lipid rafts

SDS resistant
Aggregates of p lipids
Cholesterol rich
End up in pellets if you centrifuge cell contents
Involved in signaling

68

What can cross bilayer freely

Small, nonpolar molecules
Steroid hormones
Small noncharged polar molecules

69

What can't cross protein membrane freely

Large polar molecules
Anything larger than glucose
Anything with a net charge
Any macromolecule

70

Transporter

Carrier protein
Very specific
Precise binding sites
Transport one or few at a time
Does active or passive transport

71

Uniport

One type of solute, with conformational change

72

Channel protein

Not necessarily specific
Transports many molecules at a time
Usually for ions

73

What is diffusion

Moving from an area of high concentration to an area of low concentration of solute

74

What are the two types of transport across cells

Passive
Active

75

What is passive transport

Gradient dependent. No energy used.

76

What is active transport

Energy dependent. Goes against gradient often.

77

Types of passive transport (3)

Simple diffusion
Channel mediated
Transporter mediated

78

Three types of active transport

Use ATP
Use light
Coupled transporter

79

Two types of coupled transporters

Symport
Antiport

80

What are the types of ATP driven pumps 4

P-type
ABC transporter
V-type proton pump
F-type ATP synthase

81

P-type pumps 3

For ions
Multi pass
Phosphorylate themselves during pumping cycle

82

ABC transporter

Organic molecules (amino acids, sugars)
Small molecules

83

v-type proton pump

Turbine like, made from different subunits, transfer H+ into organelles (lysosomes, vesicles, vacuoles) (acidity interior)

84

F-type ATP synthase

Use proton gradient across membrane t o drive synthesis of ATP and phosphate. Bacteria, PM, mito, chloroplasts.

85

Types of ABC transporters

Bacterial
Eukaryotic

86

How do abc transporters for bacteria work

Both import and export

87

How do abc transporters for eukaryotes work

Mostly export
-cytosol to extracellular space
-cytosol to membrane bound intracellular compartment
-mito to cytosol

88

What are the forces affecting transport

Concentration gradient
Membrane potential

89

What potential does plasma membrane have

Negative

90

Uniporter

Carrier protein that transports a single solute from one side of the membrane to the other

91

Occluded

Closed on both sides

92

Electrochemical gradient for animals-key players

Na+K+ATPase channels
-3Na+ out
-2K+ in
K+ leak channels
-voltage gated
-an electrical force exerted by an excess of negative charges attracting K+ into the cell balances tendency of K+ to leak down its concentration gradient

93

What are the concentrations of sodium and potassium outside and inside the animal cell?

Sodium
-outside-150 mM
-inside- 10 mM
Potassium
-outside- 10 mM
-inside- 150 mM

94

What is glucose/sodium coupled transport

Binding of glucose and sodium ion is cooperative
Most likely to happen extracellularly because of sodium concentration
Occluded only when bound
Transporter opens randomly in and out
If sodium dissociates, glucose cooperatively dissociates

95

How does glucose travel through intestinal epithelial cell

Apical membrane has coupled glucose/Na+ transporter bringing glucose into cell against concentration gradient
Low glucose concentration outside both sides of cell. High inside.
On basal membrane, passive Uniporter of glucose

96

What helps set up electrochemical gradient in plant and bacteria

V-type pump
-ATP to ADP
H+ out
Hydrogen/nutrient symport

97

Electrochemical differences between animals and plant cells on cell membrane and cytosol?

Cyrosol
Animal cell: H+ATPase into lysosome
Plant cell: H+ATPase into vacuole

Cell membrane
Animal cell: Na+K+ATPase, Na+ driven glucose symport
Plant cell: H+ATPase, H+ driven transport

98

How is osmoregulation a role of active transport?

Creates osmosis- movement of h2o across membrane
-h2o flows from [low solute] to [high solute]

99

Hypotonic solution

Low solute

100

What are the mechanics of secretions

Ions out into lumen of duct, and water follows

101

How is aquaporin lined?

One face of pore is lined with hydrophilic amino acids

102

Gram positive bacteria

Bacteria with single membrane

103

Gram negative bacteria

Bacteria with double membrane

104

Keep mucus runny

There are Cl- channels on membranes as well as water pores. Cl leaves through channels, Na leaves, and water follows.

105

Cystic fibrosis mechanics

Cl channels are blocked so ions can't leave cell, and water can't follow. Buildup outside of junk and microbes because there is no mucus to wash it away.

106

Cholera mechanics

Cholera toxin binds with adenylate Cyclase
Stimulates cAMP production
Camp binds with Cl channels and allows Cl- ions out. Water follows and causes dehydration.

107

Treatment of dehydration

Imbibe glucose, sodium and potassium so that water will follow it into tissues

108

What is facilitated diffusion

Uses proteins, is gradient driven

109

How do ABC transporters cause chemotherapy drug resistance in tumors

P-glycoprotein normally involved in excretion of toxins from cells. Overexpressed at baseline in chemotherapy-resistant tumors. Is upregulates after disease progression following chemotherapy in malignancies like leukemia and cancer.

110

PH in mito

Inside matrix 8
Intermembrane space 7

111

What is potential in mito matrix

Negative

112

What is potential in intermembrane space

There is no potential, just like in cytosol, because the outer membrane is porous and protons enter and leave at will

113

Where is ETC located

Inner mito membrane

114

How do protons travel though ETC

Exit through active transport

115

Proton motive force

Force through electrochemical gradient that drives protons back into mito matrix via thermogenins

116

Thermogenins

Uncoupling protein. Generates heat.

117

Uncoupling

Bypassing ATP synthase

118

How do ion channels select

On size and charge of atom

119

What is K+ bacterial channel made up of?

Vestibule, selectivity filter and pore helices

120

How does potassium travel through channel

k+ ions go into vestibule attached to h2o.ed into selectivity filter by pore helices. Carbonyl oxygens along wall of filter bind transiently to dehydrated K+ ions.

121

What is dipole of alpha helix

N terminal more positive
c terminal more negative

122

How do ion channels open or close

Conformation changes through stimuli

123

Four different ways ions are gated

Voltage gated
Ligand gated (extracellular)
Ligand gated (intracellular)
Mechanically gated

124

How are auditory hair cells gated

Mechanically. Sound waves cause stereocilia to tilt, opening channel and allowing ions from fluid in. Cilia are connected to each other by filaments which stretch when sound waves come through, tilting them.

125

Five key players in nerve signaling

Sodium electrochemical gradient at PM
Calcium gradient
Neurotransmitter receptors
Voltage gated ion channels
Synaptic vesicles at termini

126

What is membrane potential due to potassium and sodium pump?

-80/-90 mV

127

Where are neurotransmitter receptors

On dendrites and cell body

128

Teo types of voltage gated ion channels on neuron

Sodium ion channels that line dendrites/body/axon
Calcium ion channels at termini

129

What do synaptic vesicles at termini carry

Neurotransmitters

130

What are neurotransmitters

Small, organic molecules

131

What are the three states of voltage gated sodium ion channels? When do they happen?

Closed. Membrane is polarized at rest.
Open, membrane depolarized by stimulus
Deactivated, as membrane repolarizes after stimulus

132

How do sodium ion channels work

Two transmembrane alpha helices surround pore. Separated by sequences that form selectivity filter.
Four addnl alpha helices make up voltage sensor.
S4 helices have Arline, positive. An inactivation gate that is part of flexible loop connecting third and fourth domain acts as plug that obstruct us pore in channels inactivated state. Membrane refractory period.

133

Key steps in neuro transmission 3

1. Neurotransmitter binds to ligand gated ion channel and causes some depolarization
2. Adjacent voltage gated sodium ion channels open, causing more depolarization, which leads to action potential or nerve impulse.
3. Voltage gated calcium ion channels ole

134

Patch current recording

Records current flowing through individual channels
In small patch of membrane covering mouth of micro pipette
Tight seal bet. Pipette and membrane.
Current can enter or leave pipette only by passion through ion channel. Either attached or detached from membrane.

135

What are the functions of the membrane?

Define boundaries
Selective barriers
Cell signaling