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Eukaryotic Cell Biology > Chapter 11 > Flashcards

Chapter 11 Flashcards

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1
Q

The hydrophobic nature of the interior of the lipid bilayer is a barrier to what?

A

The passage of polar molecules

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2
Q

The lipid bilayer functions to allow cells to accumulate solutes that are what?

A

Different from their surrounding extracellular fluid

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3
Q

Cells exchange small molecules across its lipid bilayer for what processes? Give 3 processes

A
  1. The acquisition of nutrients
  2. Excretion of waste products
  3. The regulation of intracellular ion concentrations
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4
Q

Synthetic protein-free lipid bilayers show differences in their relative permeability to what kind of molecules?

A

Small molecules

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5
Q

Smaller and more hydrophobic/nonpolar a molecule is, what happens to the rate of diffusion across the membrane?

A

The faster its rate of diffusion across an artificial bilayer

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6
Q

Small molecule transport will be driven by the difference in the solute concentration across the membrane with transport occuring down a molecules what?

A

Concentration gradient

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7
Q

How quickly does small nonpolar molecules like oxygen and carbon dioxide cross a membrane?

A

Rapidly

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8
Q

Charged molecules like sodium, potassium, magnesium or calcium are relatively impermeable to a lipid bilayer due to what?

A

Their charge and high degree of hydration

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9
Q

The permeability coefficient and the calculated differences of a solute concentration across an artificial membrane can be used to calculate what?

A

A flow rate

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10
Q

Name 5 hydrophobic molecules that can pass readily through a synthetic lipid bilayer

A

Oxygen, Carbon dioxide, Nitrogen, Steroids, Hormones

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11
Q

Name 3 small uncharged polar molecules that can pass slowly through a synthetic lipid bilayer?

A

Water, Urea, Glycerol

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12
Q

Name 2 large uncharged polar molecules that pass very slowly (unless helped by transport proteins) through a synthetic lipid bilayer?

A

Glucose, Sucrose

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13
Q

Name six charged ions that are relatively impermeable to a lipid bilayer due their charge and high degree of hydration

A

Hydrogen, Nitrogen, HCO3, Potassium, Calcium, Choride, and Magnesium

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14
Q

What is this structure?

A

Transporter

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15
Q

What is this structure?

A

Channel protein

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16
Q

Which one (channel protein or transporter) undergoes a conformational change when transporting materials into/out of a cell?

A

Transporter

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17
Q

Which one (channel protein or transporter) is an aqueous pore?

A

Channel protein

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18
Q

Which one (channel protein or transporter) moves material into/out of the cell at a quicker rate?

A

Channel protein

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19
Q

The passage of polar molecules such as sugars, amino acids, nucleotides, cellular metabolites and ions across a membrane requires the use of what?

A

Transport proteins

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20
Q

Transport proteins each transport a specific class of molecules and usually only what kind of molecular species?

A

A certain molecular species within that class

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21
Q

All known transport proteins are what?

A

Multispanning transmembrane proteins

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22
Q

The structural composition of transmembrane proteins allows for the transport of what kind of molecules across a hydrophobic lipid bilayer without making direct contact?

A

Small hydrophilic molecules

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23
Q

What are the two kinds of membrane transport proteins?

A
  1. Transporters/carriers/permeases 2. Channels
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24
Q

What kind of membrane transport protein binds to the solute being transported and undergo changes in conformation to transfer the molecule across the membrane?

A

Transporters

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25
Q

What kind of membrane transport protein only weakly interact with the transported molecule and essential act as an aqueous pore for transport

A

Channel proteins

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26
Q

Solute transport is therefore faster through a channel than through a what?

A

Membrane transporter

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27
Q

Identify A: What kind of transport is this? It is a small hydrophobic molecule that can pass readily through the lipid bilayer.

A

Simple diffusion

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28
Q

Identify B and X : What kind of transport is this? Is it channel mediated or transporter mediated? Is it passive transport or active transport?

A

Channel mediated; Passive transport

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29
Q

Identify C and X: What kind of transport is this? Is it channel mediated or transporter mediated? Is it passive transport or active transport?

A

Transporter mediated; Passive transport

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30
Q

Identify Y: What kind of transport is this? Is it active or passive transport?

A

Active transport

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31
Q

What kind of transport uses only transporters and requires energy input?

A

Active transport

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32
Q

What kind of transport uses either channels or transporters with the concentration gradient?

A

Passive transport

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33
Q

Which electrochemical gradient has no membrane potential?

A

A

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34
Q

Which electrochemical gradient has a negative membrane potential inside?

A

B

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35
Q

Which electrochemical gradient has a positive membrane potential inside?

A

C

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36
Q

Which one will transport it’s materials more quickly? Which one will transport it’s materials the slowest?

A

Fastest: B; Slowest: C

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37
Q

All channels, and many transporters, work by what?

A

Facilitated diffusion or passive transport

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38
Q

Passive transport is the passage of solutes across a membrane down their what?

A

Concentration gradient

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39
Q

For an uncharged molecule, transport is influenced by what only?

A

Concentration

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40
Q

For a charged molecule, what two things influences its transport across a membrane?

A

Concentration and the electrical potential difference

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41
Q

What is the combination of the membrane potential and concentration gradient?

A

‘Electrochemical gradient’

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42
Q

If a solute is moving down its concentration gradient and with the electrical gradient the combined effect will be what?

A

Additive

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43
Q

If a solute is moving down its concentration gradient but against the electrical gradient the two properties will what?

A

Work against each other

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44
Q

Moving solutes against their electrochemical gradient requires the activity of what?

A

Membrane transporters

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45
Q

Moving solutes against their electrochemical gradient using membran transporters is an ‘active’ process that transports solutes by linking their passage to what?

A

ATP hydrolysis or an ion gradient

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46
Q

Passive transport of a molecule down its electrochemical gradient is facilited by what?

A

Reversible conformational changes in the membrane transporter proteins

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47
Q

Does a solute transported by membrane transporters get modified in any way?

A

No

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48
Q

What kind of transport in which the side the solute is delivered to is dependent on its concentration on each side of the lipid bilayer as well as the membrane potential for charged molecules

A

Passive transport

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49
Q

Changes in transporter conformation is not dependent on what?

A

Solute binding

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50
Q

Changes in transporter conformation occur at what?

A

Random

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51
Q

When is the rate of solute transport is maximal?

A

When all solute binding sites are occupied

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52
Q

Passive transport can be blocked by both what?

A

Competitive and noncompetitive inhibitors

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53
Q

Active transport is required to pump a solute against its what?

A

Electrochemical gradient

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54
Q

Active transporters depend on what for their transport activities?

A

A source of energy

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55
Q

Sources of energy for active transport can come from what three sources?

A
  1. Coupling the transport of one solute to the downhill transport of another 2. The hydrolysis of ATP3. The coupling of transport to the energy derived from light (bacteria)
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56
Q

Identify A: What kind of active transporter is this?

A

Coupled Transporter

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57
Q

Identify B: What kind of active transporter is this?

A

ATP-Driven Pump

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58
Q

Identify C: What kind of active transporter is this?

A

Light Driven Pump

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59
Q

What is the process in which the movement of one solute is dependent on the movement of another?

A

Coupled transport

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60
Q

Coupled transporters function as what two things?

A

Symporters or antiporters

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61
Q

What transporter simultaneously transfers the ‘transported’ molecule along with its ‘co-transported’ molecule in the same direction?

A

Symporters (a.k.a co-transporters)

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62
Q

What transporter pumps the ‘transported’ molecule in the opposite direction of the ‘co-transported’ molecule?

A

Antiporters (a.k.a exchangers)

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63
Q

How do both symporters and antiporters work?

A

By harvesting the energy stored in the electrochemical gradient of the co-transported ion for the transport of another molecule

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64
Q

The free-energy derived from the movement of the co-transported ion down its electrochemical gradient is used to do what?

A

Drive another solute against its gradient

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65
Q

In the plasma membrane of mammalian cells, What is the cotransported ion?

A

Sodium

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66
Q

In bacteria, yeast and other membrane bound mammalian organelles the co-transported ion is a what?

A

Proton

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67
Q

Identify A: What kind of transporter is this?

A

Uniport

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68
Q

Identify B: What kind of transporter is this?

A

Symport

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69
Q

Identify C: What kind of transporter is this?

A

Antiporter

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70
Q

Which two transporters are coupled transporters?

A

B and C

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71
Q

The sodium-glucose symporter is found where in the body?

A

The plasma membrane of intestinal or kidney epithelial cells

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72
Q

The sodium-glucose pump undergoes what kind of change during the transport process?

A

Conformational change

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73
Q

In which state (A or B) is the transporter is open to the extracellular space allowing for sodium and glucose binding?

A

state A

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74
Q

During state A, when sodium binds it induces a conformational change that increases the transporters affinity for what?

A

Glucose

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75
Q

Only when both molecules are bound will the transporter open to the what for delivery?

A

The cytosol

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76
Q

The overall result of the sodium-glucose symporter is the transport of what into the cell?

A

Sodium and Glucose (sodium moving down its electrochemical gradient essentially dragging glucose along against its gradient)

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77
Q

For the system to continue to work, the cell must remove what in order to maintain the electrochemical gradient?

A

Intracellular sodium

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78
Q

What in the plasma membrane is responsible for maintaining the sodium gradient?

A

The ATP-driven sodium/potassium pump

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79
Q

Give an example of a proton-driven symporter in E. coli.

A

Lactose permease

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80
Q

The lactose permease is a what?

A

12 transmembrane spanning protein

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81
Q

Lactose permease pumps lactose across the plasma membrane into the cytosol along with a what?

A

A proton (the co-transported ion)

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82
Q

Binding and transport is what, with the passage of lactose dependent on proton transport?

A

Cooperative

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83
Q

Active transporters that are dependent on an electrochemical gradient must have a mechanism in place to do what?

A

Maintain the gradient

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84
Q

Transport of glucose into the cell also carries along what kind of ion?

A

Sodium

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85
Q

For the system to continue to work, the cell must maintain the what?

A

Sodium electrochemical gradient

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86
Q

In what kind of cells does the plasma membrane contain an ATP-driven sodium/potassium pump responsible for maintaining the sodium gradient?

A

Mammalian cells

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87
Q

In what kind of cells is the proton gradient maintained through the activity of a proton ATPase?

A

In bacteria, yeast and several intracellular organelles

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88
Q

Which cell (animal or plant) uses the sodium driven symport?

A

Animal cell

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89
Q

Which cell (animal or plant) uses the hydrogen driven symport?

A

Plant cell

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90
Q

What kind of active transporter use the energy stored in ATP to pump ions or other solutes across a membrane?

A

Transport ATPases

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91
Q

What are four types of ATP driven pumps?

A
  1. P-type pumps2. F-type proton pumps3. V-type pumps4. ABC transporters
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92
Q

P-type pumps become what during the pumping cycle?

A

Phosphorylated

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93
Q

Many of the ion pumps involved in establishing and maintaining a what across membranes belong to the P-type pump class?

A

Gradient

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94
Q

What kind of pumps use a proton gradient to generate ATP?

A

F-type pumps

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95
Q

What is the other name for the F-type pump?

A

ATP synthases

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96
Q

Where are F-type pumps found?

A

1 Plasma membrane of bacteria2. The inner membrane of mitchondria3. The thylakoid membrane of chloroplasts

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97
Q

What kind of pumps are similar to F-type pumps but they pump protons into organelles to acidify their interior?

A

V-type pumps

98
Q

Where are V-type pumps found?

A

1 Lysosomes2. Synaptic vesicles3. Plant vacuoles

99
Q

V-type pumps are not involved in what?

A

ATP production

100
Q

What kind of transporters pump small molecules across a cell membrane?

A

ABC transporters

101
Q

All of ATP driven pumps can operate in what direction?

A

Reverse

102
Q

Under conditions in which the electrochemical potential is reversed and cytosolic ATP levels are low, channels can work to synthesize ATP from what?

A

ADP

103
Q

What kind of ATP driven pump is A?

A

P-type pump

104
Q

What kind of ATP driven pump is B?

A

F-type (and V-type) proton pump

105
Q

What kind of ATP driven pump is C?

A

ABC transporter

106
Q

What kind of P-type pump is this?

A

Calcium (Ca2+)

107
Q

What kind of ATP pump is a prototypical P-type pump?

A

The calcium ATPase pump

108
Q

What kind of cells maintain a steep calcium gradient across their plasma membrane?

A

Eukaryotic

109
Q

The calcium gradient is important for a cells response to what?

A
  1. Extracellular signals (to initiate embryonic development)2. The stimulation of muscle contraction3. Triggering secretion in secretory cells
110
Q

The calcium ATPase is localized to the plasma membrane and the what?

A

Sarcoplasmic reticulum (SR)

111
Q

What is a specialized endoplasmic reticulum that serves as an intracellular store for calcium?

A

Sarcoplasmic reticulum (SR)

112
Q

What is responsible for pumping calcium from the cytosol back into the SR after calcium stimulated muscle contraction?

A

The calcium ATPase

113
Q

The function of the calcium channel is critical for what?

A

Muscle relaxation

114
Q

The calcium pump has 10 transmembrane alpha helices with three of these forming the what?

A

central pore forming channel

115
Q

In the unphosphorylated state, the channel is open to the cytosol allowing for how many calcium ions to bind?

A

2

116
Q

Upon calcium binding, ATP is hydrolyzed and the terminal phosphate is transferred to a what?

A

an aspartic acid

117
Q

The phosphorylation event in the calcium channel triggers a conformational change that disrupts calcium binding leading to calcium release to the what?

A

SR lumen

118
Q

Phosphorylation is transient and its removal returns the channel to what state?

A

Calcium free

119
Q

What kind of pump is this?

A

Sodium potassium pump

120
Q

The sodium potassium pump is an example of what kind of pump?

A

P-type ATPase

121
Q

Where is the sodium potassium pump found?

A

The plasma membrane of all animal cells

122
Q

What is the sodium potassium pump function?

A

Maintaining the sodium gradient across the plasma membrane.

123
Q

In what kind of cells is a sodium gradient critical as it is used by other membrane pumps for the transport of most nutrients into the cell

A

Mammalian cells

124
Q

The sodium-potassium pump is an ATP-driven what? (symporter or antiporter?)

A

Antiporter

125
Q

How many sodium ions does the sodium potassium pump - pump out of the cell?

A

3

126
Q

How many potassium ions does the sodium potassium pump - pump into the cell?

A

2

127
Q

The sodium-potassium pump moves 3 positively charged ions out of the cell for every two it pumps in, it has a minor role in establishing a what across the membrane?

A

An electrical potential

128
Q

The sodium-potassium pump also maintains what by exporting sodium ions to counteract the influx of water by osmosis?

A

The osmotic balance

129
Q

The sodium-potassium pump is inhibited by what which directly competes for potassium binding?

A

Ouabain

130
Q

What are the steps outlining the workings of a sodium potassium pump?

A
  1. Three sodium ions from inside the cell first bind to the transport protein.
  2. A phosphate group is transferred from ATP to the transport protein causing it to change shape and release the sodium ions outside the cell.
  3. Two potassium ions from outside the cell then bind to the transport protein.
  4. As the phosphate is removed, the protein assumes its original shape and releases the potassium ions inside the cell.
131
Q

What transporters typically contain six membrane-spanning domains and two ATPase domains?

A

ABC transporters

132
Q

ABC transporters are characterized based on their what?

A

Polypeptide organization

133
Q

What transporters are formed through the dimerization of two polypeptide chains each containing an ATPase domain?

A

Half transporters

134
Q

The polypeptide organization of half transporters may be what? (2 answers)

A

Identical (homodimers) or they may be formed by multiple different polypeptides subunits

135
Q

What transporters encode two ATPase domains in a single polypeptide unit

A

Full transporters

136
Q

What are the largest family of membrane transport proteins?

A

Full transporters

137
Q

What kind of transporter pumps inorganic ions, amino acids, mono and polysaccharides, peptides and even proteins across extra and intracellular membranes?

A

Full transporters

138
Q

In bacteria, ABC transporters are involved in the import and export of what?

A

Molecules

139
Q

In eukaryotes, ABC transporters are involved in exporting molecules from the cell and importing substrates into what?

A

Organelles (ER and mitochondria)

140
Q

In gram negative bacteria (E. coli), ABC transporters localize where?

A

The inner membrane

141
Q

In gram negative bacteria, solutes that can freely pass across the outer membrane interact with substrate specific binding proteins in what space?

A

The periplasmic space

142
Q

Upon solute binding “shuttling” proteins undergo a conformational change that enables them to bind to the ABC transporters for what purpose?

A

Solute delivery

143
Q

The ABC transporter actively transfers the molecule across the inner membrane in a what driven manner?

A

ATP dependent manner

144
Q

Give the steps in the auxiliary transport system in bacteria

A
  1. The solute diffuses through a channel protein in the outer membrane
  2. A periplasmic substrate binding protein picks up the substance to be transported and carries it to the ABC transporter.
  3. ATP binds to an ATP hydrolyzing enzyme and is broken down to ADP, phosphate and energy
  4. The energy from the ATP powers the transport of the substrate across the membrane through the plasma membrane
145
Q

What are not open all of the time rather a specific signal triggers a change in conformation which leads to its opening (i.e. gating)?

A

Ion channels

146
Q

The channel pore narrows significantly in its what? It is a narrow opening that largely determines which ions can pass)

A

Selectivity filter

147
Q

What has a pore lined with hydrophilic amino acids which form the channel opening and hydrophobic amino acids arranged along the outside of the channel to interact with the lipid bilayer.

A

The channel

148
Q

Ion channels do not make what?

A

Aqueous ‘holes’ in the membrane;

149
Q

Ion channels are highly selective in the whats that can pass through them?

A

Ions

150
Q

Only what kind of ions (without their bound water) can pass through a specific channel?

A

The right size and charge

151
Q

Ion channels fluctuate between what two states?

A

An open and closed state (based on the presence or absence of a specific stimulus)

152
Q

What is the the property of the channel ‘opening briefly’ upon stimulation?

A

Gating

153
Q

Which ion channel is open?

A

B

154
Q

There are more than 100 different types of ion channels that differ from one another based what three characteristics?

A
  1. Ion selectivity (the types of ions that can pass through a channel)2. Gating (the conditions that influence their opening and closing)3. Their abundance and subcellular localization
155
Q

Give three kinds of stimuli that regulate channel gating

A
  1. Voltage gating (Probability of opening is controlled by membrane potential)2. Ligand gating (Chemical ligand (molecule) binding controls channel opening)3. Stress gating (Mechanical forces placed on the channel controls opening)
156
Q

What are two activities that contribute to the membrane potential?

A

Active electrogenic pumps and passive ion diffusion

157
Q

The movement of ions across a membrane, if not exactly balanced by oppositely charged ions, can be detected as an accumulation of electric charge referred to as what?

A

The “membrane potential”.

158
Q

What results from a thin layer of ions sitting close to the membrane due to their attraction to their counterparts of the other side of the membrane. All that is required for the establishment of it is the movement of only a small fraction of the total charge?

A

Membrane potential

159
Q

In what organelle does the membrane potential across the inner membrane is due to the activity of the electrogenic proton pumps?

A

In the mitochondria

160
Q

In plants and fungi, what establishes the membrane potential across the plasma membrane

A

Proton pumps

161
Q

High level of intracellular (-) charged organic molecules is balanced by the levels of what?

A

Intracellular K+

162
Q

High intracellular K+ is generated by the what in the plasma membrane?

A

Na+-K+ pump

163
Q

What channel in the plasma membrane randomly switch between an open and a closed state (i.e. regardless of conditions)?

A

K+ leak channels

164
Q

K+ channels are the main ion channels open in a resting cell making the plasma membrane more permeable to what ion than any other ion?

A

K+

165
Q

The movement of K+ out of the cell (down its concentration gradient) through the K+ leak channels transfers (+) charges outside of the cell. This leaves behind what? It generates what?

A

Unpaired (-) charges which generates the membrane potential (an electrical field).

166
Q

What kind of cells where the electrical potential across the plasma membrane is due to the passive transport of potassium ions through K+ leak channels?

A

Animal cells

167
Q

K+ leak channels makes the inside of the cell slightly more what than the outside?

A

Negative

168
Q

What pump plays a small role in generating the membrane potential by pumping 3 sodium ions out for every 2 potassium ions it pumps in?

A

The Na+/K+ pump

169
Q

Na+.K+ pump establishes a low intracellular Na+ concentration which is balanced by what?

A

A high K+ concentration

170
Q

Where do the intracellular K+ ions go?

A

They move down their concentration gradient out of the cell

171
Q

The loss of (+) charged ions leaves behind an unbalanced (-) charge generating what?

A

A charge difference across the membrane

172
Q

K+ ions will move down their gradient through what until they are balanced by their attraction to the (-) charged interior?

A

Potassium leak channels

173
Q

K+ ions will move down their gradient through potassium leak channel s until they are balanced by their attraction to the (-) charged interior. What happens next?

A

There is no net flow of ions across the membrane

174
Q

The equilibrium state is also called what?

A

The resting membrane potential

175
Q

What is the resting membrane potential in animal cells?

A

Between -20mV to -120mV

176
Q

What type of Ion channel is A?

A

Voltage-gated

177
Q

What type of Ion channel is B?

A

Ligand-gated (Extracellular Ligand)

178
Q

What type of Ion channel is C?

A

Ligand-gated (Intracellular Ligand)

179
Q

What type of Ion channel is D?

A

Mechanically gated

180
Q

If potassium leak channel is in the closed state (A), the membrane potential is zero. Why?

A

The positive and negative charges balance exactly (zero net charge on each side)

181
Q

If the potassium leak channel is in the closed state (A), the potassium leak channel has more of what inside?

A

Potassium

182
Q

If the potassium leak channel is in the open state (B), what will happen to the the potassium ions?

A

K+ ions will move down their concentration gradient (i.e out of the cell) until the membrane potential exerts a counterbalancing force preventing further K+ movement.

183
Q

What describes a condition in which the flow of (+) and (-) charged ion across a membrane is balanced such that no difference in charge accumulates?

A

The resting membrane potential

184
Q

What is measured as a voltage difference across the membrane and in animal cells it ranges from -20mV to -200mV.

A

The membrane potential

185
Q

Because the inside of the cells is more negative with respect to the outside of the cell (due to the K+ leak channels) membrane potentials are presented as what values?

A

Negative values

186
Q

In animal cells the membrane potential is a reflection of the difference of K+ concentration across the membrane since at rest this is the what?

A

Primary ion moved

187
Q

The bacterial K+ channel is composed of how many identical transmembrane subunits that are arranged with (-) charged amino acids positioned at both the entrance and exit to the pore.

A

Four

188
Q

The bacterial K+ channel is composed of how many identical transmembrane subunits that are arranged with (-) charged amino acids positioned where?

A

At both the entrance and exit to the pore.

189
Q

The bacterial K+ channel has (-) charged amino acids block the entry of what kind of ions?

A

(-) charged ions

190
Q

Each subunit of the bacterial K+ channel contributes an alpha-helix and a loop domain to the pore region to form what?

A

The selectivity filter of the channel

191
Q

(Bacterial K+ channel) What atoms of the polypeptide backbone within the loop interacts with the dehydrated K+ ions as they pass through in a single file?

A

The carbonyl oxygen atoms

192
Q

What is this structure?

A

Bacterial K+ channel

193
Q

(Bacterial K+ channel) What ion that has lost its bound water can enter the pore and interact with the carbonyl oxygens that line the pore?

A

K+ ion

194
Q

The carbonyl oxygens are spaced to accommodate what?

A

A dehydrated K+ ion

195
Q

The energy required to dehydrate a K+ ion is balanced by what?

A

The energy regained by the interaction of the ion with the carbonxyl oxygens

196
Q

How does the carbonyl oxygens in the pore select the ion?

A

The spacing

197
Q

What kind of ion is too small to interact with the oxygens and is therefore unable to compensate for the energy expense associated with the loss of water molecules required for its entry?

A

A sodium ion

198
Q

Identify which ion is X? (Sodium or Potassium?)

A

Potassium

199
Q

Identify which ion is Y? (Sodium or Potassium?)

A

Sodium

200
Q

Which ion channel gate is open (A or B?)

A

B

201
Q

Which ion channel gate is closed (A or B?)

A

A

202
Q

Ion channel gating: the opening and closing of what?

A

The channel pore

203
Q

Ion channel gating involves the movement of what that line the pore within the membrane?

A

The transmembrane helices

204
Q

The movement of the transmembrane helices that line the pore either blocks or opens the pathway for what?

A

Ion movement

205
Q

What kind of movement does the transmembrane helices move depending on the type of the channel?

A

Described as a tilting, rotating or bending of the transmembrane helices depending on the type of channel

206
Q

Ion channels allow for the flux of ions across a membrane without the co-passage of what?

A

Water

207
Q

Specialized channels exist in prokaryotes and eukaryotes that allow for the specific transport of water without the passage of what?

A

Ions

208
Q

What are specialized channels exist in prokaryotes and eukaryotes that allow for the specific transport of water without the passage of ions?

A

Aquaporins

209
Q

How is an aquaporin constructed?

A

It is formed from four homomeric subunits with each monomer containing a water conducting pore

210
Q

What kind of molecules pass through aquaporins in a single file and follow the carbonyl oxygens that line the pore?

A

Water

211
Q

Ions are unable to pass through the aquaporin because the pore diameter is too small for the passage of hydrated ions and the presence of hydrophobic amino acids on one face of the pore is not energetically favorable for the passage of what?

A

Dehydrated ions

212
Q

Some aquaporins allow the passage of what?

A

Glycerol and small sugars

213
Q

What are also known as “exchangers”

A

Antiporters

214
Q

What is the number of potassium ions moved per ATP by the sodium-potassium pump?

A

Two

215
Q

What is the transport process mediating solute movement against its concentration gradient?

A

Active transport

216
Q

What cannot diffuse through a lipid bilayer due to charge and hydration?

A

Ions

217
Q

What class of ATP-driven pump undergoes autophosphorylation?

A

P type

218
Q

What is the direction of sodium movement by the sodium-potassium pump?

A

Out of the Cell

219
Q

What is primarily responsible for generating the membrane potential in animal cells?

A

Potassium Leak Channels

220
Q

The plasma membrane sodium-calcium exchanger is driven by the concentration of what ion?

A

Sodium

221
Q

What is the most abundant intracellular cation?

A

Potassium

222
Q

What is the narrowest part of an ion channel; determines which ions can pass?

A

Selectivity filter

223
Q

What describes the difference in electrical charge across a membrane?

A

Membrane potential

224
Q

What is the net driving force generated by solute concentration gradient and electrical gradient?

A

Electrochemical gradient

225
Q

Their movement of solutes across a membrane requires a change in conformation

A

Carriers

226
Q

What transport process is mediated by channel proteins; no energy input required?

A

Passive transport

227
Q

What form a narrow hollow pore for the passage of watersoluble molecules across a membrane?

A

Channels

228
Q

No net flow of ions across the plasma membrane

A

Resting membrane potential

229
Q

What is the property controlling the opening and closing of an ion channel?

A

Gating

230
Q

What inhibitor blocks potassium binding to the sodium potassium pump?

A

Ouabain

231
Q

Animal cells spend one-third of their energy driving what pump?

A

Sodium Potassium ATPase

232
Q

What is the bacterial ‘equivalent’ of the sodium-potassium pump?

A

Proton pump

233
Q

What mediates the transport of a single solute across a membrane?

A

Uniporter

234
Q

What is the direction of calcium movement by the sodium-calcium exchanger?

A

Out of the cell

235
Q

What can rapidly diffuse across a lipid bilayer?

A

Oxygen

236
Q

What are water channels?

A

Aquaporins

237
Q

What is a co-transport mechanism in which the two solutes are moved in the same direction across a membrane?

A

Symporter

238
Q

What is the transport process in which solutes are moved ‘through’ a cell; e.g. the movement of glucose across an epithelial cell?

A

Transcellular

239
Q

What is the most abundant extracellular cation?

A

Sodium

240
Q

The SR localized Ca2+ pump moves what number of calcium ions per ATP hydrolyzed?

A

Two

Eukaryotic Cell Biology (7 decks)

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