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Cell Biology > Exam 2 > Flashcards

Exam 2 Flashcards

0
Q

What are a couple of tools cells use for movement?

A

Shape change

Flagella

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1
Q

What are the functions of the membrane?

A

Define boundaries
Selective barriers
Cell signaling

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2
Q

What is meant by “dynamic” when we talk about the membrane

A

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

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3
Q

What are the major lipid bilayer components

A

Amphipatic lipids
Proteins
Carbohydrates

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4
Q

How much of membrane does each component make up?

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

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

A

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

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6
Q

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

A

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.

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7
Q

What force drives the shape of the lipid bilayer?

A

Hydrophobic forces

Van der waals forces

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8
Q

What lipid is only found in eukaryotes?

A

Sterols

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9
Q

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

A

Help protect plasma membrane

Cell to cell signaling

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10
Q

How can one change the fluidity of a membrane?

A

Change fatty acid length

Change fatty acid saturation/desaturation

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11
Q

How is a membranes fluidity helpful?

A

Allows cells to fit surroundings

Prevents membrane from becoming leaky

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12
Q

How can we chemically control a membranes fluidity

A

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

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13
Q

What are phospholipids made of

A

Glycerol, two fatty acids with a polar head

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14
Q

Are both fatty acids saturated in a phospholipid?

A

No. One is saturated. The other is unsaturated.

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15
Q

What phospholipid is important in signaling

A

Phosphatidyl inositol

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16
Q

Why do hydrophobic forces roll lipid into ball

A

More energetically favorable

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17
Q

How do we use synthetic vesicles

A

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

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18
Q

What is the structure of a sterol?

A

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

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19
Q

What is the function of a sterol

A

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

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20
Q

What is attached to lipid in glycolipids

A

Sugars

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21
Q

What kind of fluid is the lipid bilayer

A

Two dimensional

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22
Q

What can change fluidity of lipid bilayer?

A

Temperature

Chemical composition

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23
Q

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

A

It is less saturated

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24
Q

How does organism adjust to temperature change?

A

Change fluidity of membrane

Control total cholesterol

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25
Q

How does one change fluidity of membrane?

A

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

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26
Q

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

A

Those with shorter tails

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27
Q

What happens to fluidity if cholesterol increases?

A

It decreases

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28
Q

What kind of bond exists phospholipid and cholesterol on lipid membrane

A

Hydrogen bond

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29
Q

What technique is used to measure membrane fluidity

A

Fluorescence recovery after photo bleaching

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30
Q

three steps of FRAP

A
  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.
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31
Q

Why are lipid bilayers asymmetrical?

A

Leaflets are different, have different chemical compositions

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32
Q

Why are lipid bilayers asymmetrical

A

So cell knows which way is up and down

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33
Q

How is membrane generated and maintained

A

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

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34
Q

What are flip passes in ER

A

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

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35
Q

How is new membrane sent out of ER

A

Vesicles

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36
Q

What happens if a protein is inserted backwards

A

It may not work

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37
Q

In Golgi, what do sugars never face?

A

The cytosol

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38
Q

Four purposes of proteins

A

Transporters
Anchors
Receptors
Enzymes

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39
Q

Two types of membrane proteins

A

Peripheral

Integral

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40
Q

Peripheral protein

A

Loosely associated

Noncovalent interaction with integral protein or lipid

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41
Q

Integral protein

A

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

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42
Q

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

A

Vertical

One

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43
Q

Multi pass

A

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

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44
Q

Beta barrels

A

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

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45
Q

Porins

A

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

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46
Q

Lipid linked protein

A 
Post translational modifications
Palmitoylation
Prenylation
Protein is anchored to bilayer even though amino acids do interact
Lipid linkages allow for fast diffusion
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47
Q

Palmitoylation

A

Covalent attachment of fatty acid

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48
Q

Prenylation

A

Addition of hydrophobic molecule to protein or chemical compound

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49
Q

How does one study integral membrane proteins

A

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

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50
Q

SDS

A

Strong a ionic detergents

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51
Q

Why difficult to study integral protein

A

Nonpolar

Highly insoluble, hard to purify, hard to study

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52
Q

Book method to study integral proteins

A
  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
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53
Q

Oleate

A

Fatty acid with one kink

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54
Q

Stearate

A

Saturated fatty acid

55
Q

What are cell solutions for having a weak lipid bilayer?

A

Cell cortex
Glycocalyx
Cell walls
Tight junctions

56
Q

Cell cortex

A

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

57
Q

Glycocalyx

A 
Carb layer
On outside of PM
Protective layer in animal cells
Like a loose cell wall
Importsnt for cell cell attachment
58
Q

Where do we find cell walls

A

Fungi, plants, bacteria

59
Q

How do neutrophils slow down in veins

A

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

60
Q

What would happen if there were no tight junctions

A

Proteins would end up on any side of the cell

61
Q

Why is fluid mosaic model flawed

A

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

62
Q

What does cell polarity mean

A

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

63
Q

How is protein movement restricted (3)

A

Cell cortex
Extracellular matrix
Proteins on adjacent cells

64
Q

Apical vs basolateral

A

Apical faces lumen. Basolateral is bottom

65
Q

How so do we track protein movement

A

Fluorescence

66
Q

What are micro domains

A

Lipid rafts

67
Q

What are lipid rafts

A 
SDS resistant
Aggregates of p lipids
Cholesterol rich 
End up in pellets if you centrifuge cell contents
Involved in signaling
68
Q

What can cross bilayer freely

A

Small, nonpolar molecules
Steroid hormones
Small noncharged polar molecules

69
Q

What can’t cross protein membrane freely

A

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

70
Q

Transporter

A 
Carrier protein
Very specific
Precise binding sites
Transport one or few at a time
Does active or passive transport
71
Q

Uniport

A

One type of solute, with conformational change

72
Q

Channel protein

A

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

73
Q

What is diffusion

A

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

74
Q

What are the two types of transport across cells

A

Passive

Active

75
Q

What is passive transport

A

Gradient dependent. No energy used.

76
Q

What is active transport

A

Energy dependent. Goes against gradient often.

77
Q

Types of passive transport (3)

A

Simple diffusion
Channel mediated
Transporter mediated

78
Q

Three types of active transport

A

Use ATP
Use light
Coupled transporter

79
Q

Two types of coupled transporters

A

Symport

Antiport

80
Q

What are the types of ATP driven pumps 4

A

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

81
Q

P-type pumps 3

A

For ions
Multi pass
Phosphorylate themselves during pumping cycle

82
Q

ABC transporter

A 
Organic molecules (amino acids, sugars)
Small molecules
83
Q

v-type proton pump

A

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

84
Q

F-type ATP synthase

A

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

85
Q

Types of ABC transporters

A

Bacterial

Eukaryotic

86
Q

How do abc transporters for bacteria work

A

Both import and export

87
Q

How do abc transporters for eukaryotes work

A

Mostly export

  • cytosol to extracellular space
  • cytosol to membrane bound intracellular compartment
  • mito to cytosol
88
Q

What are the forces affecting transport

A

Concentration gradient

Membrane potential

89
Q

What potential does plasma membrane have

A

Negative

90
Q

Uniporter

A

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

91
Q

Occluded

A

Closed on both sides

92
Q

Electrochemical gradient for animals-key players

A 
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
Q

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

A 
Sodium
-outside-150 mM
-inside- 10 mM
Potassium
-outside- 10 mM
-inside- 150 mM
94
Q

What is glucose/sodium coupled transport

A

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
Q

How does glucose travel through intestinal epithelial cell

A

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
Q

What helps set up electrochemical gradient in plant and bacteria

A

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

97
Q

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

A

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
Q

How is osmoregulation a role of active transport?

A

Creates osmosis- movement of h2o across membrane

-h2o flows from [low solute] to [high solute]

99
Q

Hypotonic solution

A

Low solute

100
Q

What are the mechanics of secretions

A

Ions out into lumen of duct, and water follows

101
Q

How is aquaporin lined?

A

One face of pore is lined with hydrophilic amino acids

102
Q

Gram positive bacteria

A

Bacteria with single membrane

103
Q

Gram negative bacteria

A

Bacteria with double membrane

104
Q

Keep mucus runny

A

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

105
Q

Cystic fibrosis mechanics

A

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
Q

Cholera mechanics

A

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
Q

Treatment of dehydration

A

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

108
Q

What is facilitated diffusion

A

Uses proteins, is gradient driven

109
Q

How do ABC transporters cause chemotherapy drug resistance in tumors

A

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
Q

PH in mito

A

Inside matrix 8

Intermembrane space 7

111
Q

What is potential in mito matrix

A

Negative

112
Q

What is potential in intermembrane space

A

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

113
Q

Where is ETC located

A

Inner mito membrane

114
Q

How do protons travel though ETC

A

Exit through active transport

115
Q

Proton motive force

A

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

116
Q

Thermogenins

A

Uncoupling protein. Generates heat.

117
Q

Uncoupling

A

Bypassing ATP synthase

118
Q

How do ion channels select

A

On size and charge of atom

119
Q

What is K+ bacterial channel made up of?

A

Vestibule, selectivity filter and pore helices

120
Q

How does potassium travel through channel

A

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
Q

What is dipole of alpha helix

A

N terminal more positive

c terminal more negative

122
Q

How do ion channels open or close

A

Conformation changes through stimuli

123
Q

Four different ways ions are gated

A 
Voltage gated
Ligand gated (extracellular)
Ligand gated (intracellular)
Mechanically gated
124
Q

How are auditory hair cells gated

A

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
Q

Five key players in nerve signaling

A 
Sodium electrochemical gradient at PM
Calcium gradient
Neurotransmitter receptors
Voltage gated ion channels
Synaptic vesicles at termini
126
Q

What is membrane potential due to potassium and sodium pump?

A

-80/-90 mV

127
Q

Where are neurotransmitter receptors

A

On dendrites and cell body

128
Q

Teo types of voltage gated ion channels on neuron

A

Sodium ion channels that line dendrites/body/axon

Calcium ion channels at termini

129
Q

What do synaptic vesicles at termini carry

A

Neurotransmitters

130
Q

What are neurotransmitters

A

Small, organic molecules

131
Q

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

A

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

132
Q

How do sodium ion channels work

A

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
Q

Key steps in neuro transmission 3

A
  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
Q

Patch current recording

A

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.

Cell Biology (35 decks)

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