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BIO107 - CELL AND MOLECULAR BIOLOGY > 4 - Membrane Transport > Flashcards

4 - Membrane Transport Flashcards

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1
Q
  • restricts passage of most polar molecules
  • different concentration of solutes in the cytosol and extracellular fluid
  • membrane transport proteins
  • transporters and channels
A

Membrane transport

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2
Q

2 main classes of membrane proteins

A
  1. Transporter (carriers)
  2. Channels
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3
Q

3 Solute carrier (SLC) transporters

A
  1. Uniporter
  2. Symporter
  3. Antiporter
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4
Q

An ABC transporters

A

pump

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5
Q

Principles of membrane transport

A

transport by carriers can be either active or passive, solute flow through channel proteins is always passive.

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6
Q

Moevement of solute in uniporter

A

facilitated diffusion

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7
Q

Symporter, antiporter, and pump move solute using active or passive transport?

A

Active transport

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8
Q

uses primary active transport

A

pump

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9
Q

Use secondary active transport

A

Symporter and antiporter

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10
Q

lipid bilayers are impermeable to ___

A

ions

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11
Q

The passage of molecules across membrane depends on ___ and _____

A

size and hydrophobicity

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12
Q

Example of hydrophic molecules

A
  1. O2
  2. CO2
  3. N2
  4. Steroid hormones
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13
Q

Example of small uncharged polar molecules

A
  1. H2O
  2. Urea
    3.Glycerol
  3. NH3
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14
Q

Example of large uncharged polar molecules

A
  1. glucose
  2. Sucrose
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15
Q

Example of ions

A
  1. H+
  2. Na+
  3. HCO3-
  4. K+
  5. Ca2+
  6. Cl-
  7. Mg2+
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16
Q

transfer solutes across cell
membranes

A

membrane transport proteins

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17
Q
  • transfer specific molecular
    species or a class of molecules
  • highly specific
A

transport proteins

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18
Q

Example genetic disorder that is due to single-gene mutation in transport proteins

A

cystinuria

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19
Q
  • single-gene mutation
  • autosomal-recessive defect in the reabsorptive transport of cystine from the urine or intestine into the bloodstream.
  • Csytine accumulates in the urine. This build up leads to the formation of cystine stones in the kidney
A

cystinuria

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20
Q

All membrane proteins that have been studied in detail are ____ ____ ___

A

multipass transmembrane
proteins

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21
Q

means that their polypeptide chain cross the lipid bilayer multiple times

A

multipass transmembrane protein

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22
Q

pathway formed by membrane proteins which allows specific hydrophobic solutes to cross

A

protein-lipid pathway

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23
Q

transporters are also known as

A

carriers or permeases

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24
Q
  • bind
  • conformational changes
A

transporters

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25
Q

form continuous pores

A

channels

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26
Q

“downhill” transfer

A

passive transport

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27
Q

Movement of uncharged molecule across membrane is driven by

A

concentration gradient

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28
Q

Movement of charged molecule aross membrane is driven by

A

membrane potential

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29
Q
  • uphill
  • against their electrochemical
    gradients
A

active transport

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30
Q

In most biological cells, the inside of the cell has ___ ___ ___

A

Negative electrical potential

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31
Q

negative
insided

A

electrical potential

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32
Q

Tightly coupled with energy

A

transporter

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33
Q

Process by which transporter transfer a solute resembles an ___-___ reaction

A

enzyme-substrate react

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34
Q

transporters have specific ___ sites for its solute

A

binding

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35
Q

transporters undergo a ___ ___ ___ after binding to their substrate molecules.

A

reversible conformational change

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36
Q

In some transporter proteins, an intermediate state called the ___ state exists during the transport cycle

A

occluded

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37
Q

represents a conformation where the binding site for the substrate is inaccessible from either side of the membrane.

A

Occluded state

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38
Q

3 Confirmational changes in transporters

A
  1. Outward-open
  2. Occluded
  3. Inward-open
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39
Q

3 main ways for cells to perform active transport

A
  1. Coupled transport
  2. ATP -driven pumps
  3. Light-or-redox-driven pumps
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40
Q

use energy stored in concentration gradients

A

Coupled transport

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41
Q

used energy from hydrolysis of ATP

A

ATP-driven pumps

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42
Q

Use energy from light

A

light- or redox-driven pumps

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43
Q

2 main type of transporter

A
  1. Uniporter
  2. Coupled transporters
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44
Q
  • passive transport
  • move one type of solute across membrane
A

uniporters

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45
Q
  • transfer of one solute depends on the
    transport of a second
  • move 2 different solute at the same time
A

Coupled transporters

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46
Q

2 types of coupled transporters

A
  1. Symporters
  2. Antiporters
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47
Q
  • transfer 2 different solute in the same direction
A

Symporters

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48
Q

transfer 2 different solute in the opposite direction

A

Antiporters

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49
Q

harvest energy stored in the electrochemical gradient

A

Coupled transport

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50
Q

Example of coupled transporters

A
  • Na+ - co-transported ion
  • Na+-K+ pump
  • Na+-driven symporters
  • Na+ and glucose, and neurotransmitters
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51
Q

Example of symporter

A

Na+ - co-transported ion

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52
Q

Example of primary active transporter

A

Na+-K+ pump

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53
Q

Transporters have 10 or more ___ ____ that span
the membrane

A

a helices

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54
Q

are located midway through
the membrane

A

solute- and ion-binding sites

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55
Q
A
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56
Q

Allows the transporter to alternately open and close on other side of membrane

A

pseudosymmetric or inverted repeats
structure

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57
Q

Inverted repeats are also known as

A

pseudosymmetric

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58
Q

2 channels that evolved from coupled transporter in which gating mechanism were lost, allowing the channels to open simultaneously on both sides of the membrane

A

aquaporin water channel and
the Sec61 channel (ER)

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59
Q

3 classes of ATP-driven pumps

A
  1. P-type pumps
  2. ABC (ATP-binding cassette) transporters
  3. V-type pumps
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60
Q

-phosphorylates
-phosphorylate themselves during the transport cycle

A

P-type pumps

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61
Q

-pump small molecules

A

ABC (ATP-binding cassette) transporters

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62
Q
  • turbine-like
  • made from multiple different subunits
  • pumps H+ ions into organelles like lysosomes, vacuoles, and synaptic vesicle
A

V-type pumps

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63
Q

structurally related to V-type pumps but function in reverse manner

A

F- type (ATP synthase)

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64
Q

use the H+ gradient across the membrane to drive synthesis of ATP

A

F-type (ATP synthase)

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65
Q

Pumps Ca2+ into the sarcoplasmic reticulum in muscle cells

A

P-type ATPase

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66
Q

pumps Ca2+ out of the cell

A

Ca2+ ATPase

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67
Q

intracellular storage of Ca2+ in
muscle cells

A

sarcoplasmic reticulum

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68
Q

release of Ca2+ into the cytosol (Ca+-release channels) can trigger ____ _____

A

muscle contraction

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69
Q

P-type ATPase structure

A

10 transmembrane α helices
connected to three cytosolic
domains

70
Q

3 cytosolic domains

A
  1. nucleotide-binding domain
    (N)
  2. phosphorylation domain (P)
  3. activator domain (A)
71
Q

Binds and hydrolyzes ATP, providing the energy needed for ion transport.

A

nucleotide-binding domain
(N)

72
Q

Becomes phosphorylated during the transport cycle, which is essential for the conformational changes that drive ion transport

A

phosphorylation domain (P)

73
Q

Regulates the dephosphorylation of the P-domain and resets the pump after each cycle.

A

activator domain (A)]

74
Q

established Na+
and K+ gradient across the
plasma membrane

A

Na+-K+ pump/Na+-K+ ATPase

75
Q

Has higher concentration in the cell

A

K+

76
Q

Has low concentration in the cell

A

Na+

77
Q

Na+-K+ pump has ___-____ antiporter

A

ATP-driven antiporter

78
Q

___ out, ____ in

A

Na+
K+

79
Q

Na+-K+ pump regulate ____ __

A

cytosolic pH

80
Q

The pump creates an ____ because it moves more positive charges (Na⁺) out than it brings in (K⁺), contributing to the cell’s negative internal charge.

A

electrogenic

81
Q

create an
electric potential

A

electrogenic

82
Q

-contains highly conserved ATPase domains (ATP-binding
“cassettes)

A

ABC transporters

83
Q

ABC transporters contains highly conserved ______ ______

A

ATPase domains (ATP-binding cassettes)

84
Q

brings together two domains

A

ATP binding

85
Q

leads to domain dissociation

A

ATP hydrolysis

86
Q

alternately expose solute-binding sites

A

ABC transporters

87
Q

ABC transporters expose their ___-___ sites alternately

A

solute-binding sites

88
Q

ABC transporters were first found in ____

A

bacteria

89
Q

In bacteria, it captures nutrients and deliver them to ABC transporters

A

auxiliary mechanism

90
Q

-pump hydrophobic drugs out of the cytosol

A

ABC transporter

91
Q

What do ABC transporters pump out of the cytosol?

A

hydrophobic drugs

92
Q
  • A member of ABC transporter family that pump hydrophobic drugs out of
    the cytosol
  • present at elevated levels in human cancer cells and makes the cell simultaneously resistant to a variety of chemically unrelted cytotoxic drugs that are widely used in cancer chemotherapy
A

multidrug resistance (MDR) protein
or P-glycoprotein

93
Q

causes malaria, pumps out chloroquine

A

Plasmodium falciparum

94
Q

P. falciparum have amplified a gene encoding an ABC transporter that pumps out ___

A

chloroquine

95
Q

TAP transporter

A

transporter associated with
antigen processing

96
Q

-pumps peptides from the cytosol to ER lumen

A

transporter associated with
antigen processing (TAP transporter)

97
Q

peptides in cytosol are prodced by?

A

protein degradation in proteasomes

98
Q

peptides are carried from ER to ___ ___, where they are displayed for scrutiny by cytotoxic T lymphocytes

A

cell surface

99
Q

-scrutinize the peptides on the cell surface
- kills the cell if the peprides are derived from virus or other microorganism

A

cytotoxic T lymphocytes

100
Q
  • member of the ABC transporter family which was discovered through studies of cystic fibrosis
    -Cl- transport protein
  • regulates ion concentrations in the extracellular fluid, esp. in lung
A

cystic fibrosis transmembrane conductance regulator protein (CFTR)

101
Q

caused by mutation in the gene encoding CFTR

A

cystic fibrosis

102
Q
  • form pores across membrane
    -one class found in virtually all animals forms gap junctions between adjacent cell
  • not energy coupled, “downhill”
  • diffuse down electrochemical
    gradients
A

Channels

103
Q

– connects the cytoplasm of two cells

A

gap junctions

104
Q
  • inorganic ion transport
A

ion channels

105
Q
  • water channels
  • allow water to move more rapidly
  • narrow pore that allows water molecules to traverse the membrane in single file
A

aquaporins

106
Q

2 properties of ion channels that distinguish them from aqueous pores

A
  1. Ion selectivity
  2. gated
107
Q

-allow inorganic ions to pass
- has selectivity filters

A

ion selectivity

108
Q

the permeating ions have to shed most or all of their water molecules to pass through the narrowest part of the channel called____

A

selectivity filters

109
Q

4 Main types of stimuli known to cause ion channels to open

A
  1. Voltage-gated
  2. Ligand-gated (extracellular ligand)
  3. Mechanically gated
110
Q

open briefly and then close again

A

gated

111
Q

2 typesnof ligand-gated channel

A
  1. Extracellular mediator
  2. Intracellular mediator
112
Q

extracellular mediator

A

transmitter-gated channel

113
Q

intracellular mediator

A

ion-gated channels or
nucleotide-gated channels

114
Q
  • voltage-gated
  • membrane potential
  • K+ leak channels
  • active electrogenic pumping and
    from passive ion diffusion
A

ion channels

115
Q

Opens even in an unstimulated or “resting” cell

A

K+ leak channels

116
Q

purpose of k+ leak channels

A

making plasma membrane much mkre permeable to K+ than to other ions.

117
Q

bacterial K+ channels are made from

A

4 identical transmembrane subunits

118
Q

Together form a central pore through the membrane

A

four identical transmembrane
subunits

119
Q

selectivity filter

A

pore helix

120
Q

each four identical transmembrane
subunits contributes two transmembrane __ ____

A

a helices

121
Q

the polypeptide chain that connects the 2 transmembrane helices forms a short __ __ and ___ ___

A

a helix (pore helix) and crucial loop

122
Q

pore helix and crucial loop that protrudes into the wide section of cone to form ___

A

selectivity filter

123
Q

To enter selective filter, K+ ions must?

A

K+ ion must lose almost all of its
bound water molecules

124
Q

K+ ions interact with ___ ___ lining the filter

A

Carbonyl oxygen

125
Q

oxygen are rigidly spaced at the exact distance to accomodate a __

A

K+ ion

126
Q

Cannot enter selectivity filter because the carbonyl oxygen are too far away from them to compensate for the energy expense associated with the loss of water molecules required for entry

A

Na+ ions

127
Q

What do the structure of a closed K+ channel shows

A

tilting the inner helices

128
Q

structural and functional diversity of voltage-gated Ca2+ channels is due to

A

alternative splicing of RNA transcripts

129
Q

Voltage-gated Ca2+ (also K+ and Na+) channels belong to a __ superfamily

A

large

130
Q

Cause of nerve, muscle, brain, or heart disease

A

mutant genes encoding ion
channels

131
Q

mutation in genes that encode voltage-gated Na+ channels in skeletal muscle cells can cause ___

A

myotonia

132
Q

A condition in which there is a delay in muscle cell relaxation after voluntary contraction, causing painful muscle spasms

A

myotonia

133
Q

mutation in genes that encode Na+ or K+ channels in the brain can cause ___

A

epilepsy

134
Q

-mechanically gated ion channels
-capable of responding to mechanical forces
- extremely rare channel

A

mechanosensitive channels

135
Q

How many mechanically gated ion
channels are found in hair cells of human cochlea

A

50-100

136
Q

Open in response to mechanical stretching of the lipid bilayer

A

mechanosensitive channels found in bacterial plasma membrane

137
Q

mechanical stretching of the
lipid bilayer

A

hypotonic

138
Q

When bacterium experience hypotonic condition, what happens tomthe cell

A

Cell swells as water seeps in due to an increase in the osmotic pressure

139
Q

It will open when pressure rises to dangerous levels to allow small molecules to leak out

A

mechanosensitive channels

140
Q

receive, conduct, and transmit signals

A

neurons

141
Q

Fundamental task of neurons

A

receive, conduct, and transmit signals

142
Q

Despite the varied significance of signaks carried by different classes of neurons, the form of signal is always the same, consisting ?

A

changes in the electrical potential across the neuron’s plasma membrane

143
Q

-traveling wave of electrical excitation
- carry a message without attenuation from one end of a neuron to the other
- consequence of the properties of voltage-gated cation channels

A

action potential or nerve impulse

144
Q
  • electrically excitable cells
  • responsible for generating the action potentials
A

voltage-gated cation channels

145
Q

triggers an actional potential

A

depolarization of the plasma membrane

146
Q

In nerve and skeletal cells, a stimulus that causes sufficient depolarization promotly open ___

A

open Na+ channels

147
Q

open Na+ channels, Na+ enters the cell

A

self-amplification
process

148
Q

The electrical potential in the local region of membrane has shifted from its resting value of about

A

-40mV to +50mV

149
Q
  • photosensitive ion channels
  • contains covalently bound retinal group
  • light-driven cation channel
  • revolutionized the study of neural circuits
A

channelrhodopsins

150
Q
  • increase the rate at which the axon can conduct an action potential
  • formed by glial cell
A

myelination

151
Q

myelin is formed by

A

glial cells

152
Q

glial cells that myelinte axons in peripheral nerves

A

Schwann cells

153
Q

glial cells that myelinte axons in central nervous system

A

oligodendrocytes

154
Q

little current can leak across it

A

myelin

155
Q
  • interrupt myelin sheath
  • where almost all the Na+ channelsnin the axon are concentrated
    -allows for saltatory conduction
A

nodes of Ranvier

156
Q
  • demyelinating disease
  • immune system destroys myelin sheaths in some region of CNS
A

multiple sclerosis

157
Q

where neuronal signals are transmitted

A

synapses

158
Q

____ cell – ____cleft – ____cell

A

presynaptic cell – synaptic cleft –
postsynaptic cell

159
Q

Release of neurotransmitter is from

A

presynaptic cell

160
Q

neurotransmitter bins to and opens

A

transmitter-gated ion channel in the postsynaptic cell

161
Q

transmitter-gated ion channel as receptor

A

highly selective binding sites

162
Q

-highly selective binding sites
- selective in the type of ions that they let pass across the plasma membrane
-neurotransmitter receptors

A

transmitter-gated ion channel

163
Q
  • open cation channels
  • influx of Na+ or Ca2+
  • firing an action potential
A

excitatory neurotransmitters

164
Q
  • open Cl- or K+ channels
  • suppresses firing
A

inhibitory neurotransmitters

165
Q

Used as excitatory neurotransmitters

A

acetylcholine, glutamate, serotonin

166
Q

Used as inhibitory neurotransmitters

A

γ-aminobutyric acid (GABA) and glycine

167
Q

2 major classes of neurotransmitter receptors

A

ionotropic receptors
metabotropic receptors

168
Q

ion channels and feature at fast chemical
synapses

A

ionotropic receptors

169
Q

– G-protein coupled receptors that bind to all
other neurotransmitte

A

metabotropic receptors

170
Q
  • well-studied transmitter-gated ion channel
  • composed five transmembrane polypeptides
A

acetylcholine receptors

171
Q

__ acetylcholine binds →___change → ___
channe

A

two
conformational
open

172
Q

involves the sequential activation of five
different sets of ion channels

A

neuromuscular transmission

BIO107 - CELL AND MOLECULAR BIOLOGY (5 decks)

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