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BMS 521 > Exam 2 > Flashcards

Exam 2 Flashcards

1
Q

What does the plasma membrane do?

A

defines the cell and separates the inside from the outside

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2
Q

In eukaryotes, what else does the plasma membrane do?

A

defines intracellular organelles

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3
Q

What does the plasma membrane consist of?

A

a lipid bilayer that is semipermeable

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4
Q

What does the plasma membrane regulate?

A

the transport of materials into and out of the cell

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5
Q

What are the functions of the plasma membrane?

A

-hold structure
-protection
-transport
-communication through cell-cell signaling
-energy transportation

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6
Q

What is the basic structural unit of biological membranes?

A

phospholipid bilayer

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7
Q

What prevents water-soluble substances from crossing the membrane?

A

its hydrophobic core

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8
Q

What does the fluid mosaic model do?

A

keeps organelle shape and enables membrane budding and fusion/fission

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9
Q

What things give mosaic structure and fluid character?

A

phospholipids
cholesterol
proteins
carbohydrates

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10
Q

What are the principal building blocks of membranes?

A

phospholipids

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11
Q

What is the most common phospholipid in membranes?

A

phosphoglycerides

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12
Q

What does amphipathic mean?

A

molecules consists of 2 different properties

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13
Q

What makes phospholipids amphipathic?

A

hydrophobic tail made of fatty acids
hydrophilic head

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14
Q

What are the 3 amphipathic lipids in membranes?

A

phospholipids, glycolipids, cholesterol

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15
Q

What determines the structure of membranes?

A

the interactions between phospholipids with each other and water

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16
Q

How do phospholipids form bilayers?

A

hydrophobic tails align tightly together in the center, forming a hydrophobic core
hydrophilic heads face the outside

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17
Q

What stabilizes the close packing of non polar phospholipid tails?

A

van der Waals interactions

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18
Q

What stabilizes the interactions of the polar phospholipid head groups with water and each other?

A

ionic and hydrogen bonds

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19
Q

Exoplasmic face of bilayer

A

faces the outside

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20
Q

Cytosolic face of bilayer

A

faces the inside (cytosol)

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21
Q

What organelles are surrounded by two membranes (2 lipid bilayers)?

A

nucleus, chloroplast, mitochondria

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22
Q

Structure of phosphoglycerides

A

hydrophobic tail with 2 fatty acyl chains
polar head group attached to phosphate

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23
Q

What are plasmalogens?

A

a group of phosphoglycerides that contain one chain attached to C2 of glycerol by ester linkage and the other chain attached to C1 of glycerol by ether linkage

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24
Q

Where are plasmalogens abundant?

A

brain and heart tissue

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25
Q

What are the 3 principal classes of lipids present in biomembranes?

A

phosphoglycerides, sphingolipids, sterols

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26
Q

What are sphingolipids?

A

compounds derived from sphingosine that have a long chain fatty acid attached by amide linkage

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27
Q

What is the most abundant sterol in membranes of mammalian cells?

A

cholesterol

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28
Q

What do sterols provide?

A

structural support, prevent close packing of phospholipids, maintain membrane fluidity, give rigidity

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29
Q

How are sterols incorporated into the membrane?

A

intercalating between phospholipids

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30
Q

Transmembrane proteins

A

provide gateways to permit transport of specific substances

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31
Q

What do transporters do?

A

carry molecule from one side to the other

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32
Q

What do receptors do?

A

bind extracellular molecules

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33
Q

What do enzymes do?

A

transform molecule into another form

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34
Q

What do anchor proteins do?

A

physically link intracellular structures with extracellular structures

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35
Q

What phase transition in the membrane does lowering the temp cause?

A

from fluid state to gel state

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36
Q

What phase transition in the membrane does increasing the temp cause?

A

from gel state to fluid state

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37
Q

What does phase transition affect?

A

diffusion rates

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38
Q

3 factors that influence cell membrane fluidity?

A

temp, cholesterol, saturation vs unsaturation of fatty acids

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39
Q

What does composition of plasma membrane affect?

A

membrane fluidity, thickness, curvature

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40
Q

What causes curvature in the bilayer?

A

lipid asymmetry and cholesterol symmetry cause charge differences

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41
Q

Where are phophoglycerides synthesized?

A

cytosolic face of the ER membrane

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42
Q

Where is sphingomyelin synthesized?

A

ectoplasmic face of the Golgi

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43
Q

What does the cytosolic face of the ER become?

A

cytosolic face of the plasma membrane

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44
Q

What does the ectoplasmic face of the Golgi become?

A

exoplasmic face of the plasma membrane

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45
Q

What causes activation of the cytosolic enzyme?

A

stimulation of cell surface receptors by their ligands

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46
Q

What are lipid droplets?

A

vesicular structures composed of triglycerides and cholesterol esters

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47
Q

Where do lipid droplets originate from?

A

the ER

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48
Q

What do lipid droplets do?

A

store proteins for degradation

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49
Q

What are the 3 categories that membrane proteins can be classified into?

A

integral (transmembrane) proteins
lipid-anchored membrane proteins
peripheral membrane proteins

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50
Q

What are the 3 domains of transmembrane proteins?

A

cytosolic and ectoplasmic domains (have hydrophilic amino acids)
membrane spanning domain (have hydrophobic amino acids, one or more alpha helices/beta strands)

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51
Q

Transmembrane proteins span…

A

the entire bilayer

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52
Q

Lipid-anchored membrane proteins…

A

are bound covalently to one or more lipids with only the hydrophobic tail embedded into one leaflet of the membrane to anchor the protein

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53
Q

Peripheral membrane proteins do not…

A

span the whole membrane or have direct contact to the hydrophobic core

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54
Q

How are peripheral membrane proteins bound to the membrane?

A

by interactions with integral/ lipid anchored membrane proteins or by direct interactions with lipid head groups

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55
Q

What do peripheral membrane proteins do?

A

provide an interface between the cell and its environment, determine cells shape mechanical properties, and play a role in communication between cell interior and exterior

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56
Q

Examples of transmembrane proteins

A

aquaporins, T cell receptor for antigen, GPCR, glycophorin A

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57
Q

Which transmembrane protein contains only 1 membrane spanning alpha helix, forms dimers, and is the major protein for erythrocyte plasma membrane?

A

glycophorin A

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58
Q

Which transmembrane protein has 7 membrane spanning alpha helices and has pumps activated by light that results in the pumping of protons from the cytosol into the extracellular space?

A

GPCR

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59
Q

Which transmembrane protein has 4 subunits with 6 alpha helices in each, are water/glycerol channels, and are homo-tetramers?

A

aquaporins

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60
Q

Which transmembrane protein is composed of 4 separate dimers with interactions driven by charge-charge interactions between alpha helices?

A

T-cell receptor for antigen

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61
Q

Porins are found in the outer membranes of what?

A

gram-neg. bacteria
microchondria
chloroplasts

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62
Q

What is the shape of each subunit in porins?

A

barrel shaped

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63
Q

How are porins formed?

A

16 beta strands within a subunit form a sheet that twists into a barrel shape with a pore in the center

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64
Q

How do covalently attached lipids anchor some proteins to membranes?

A

acylation (cytosolic surface)
prenylation (cytosolic surface)
GPI anchor (exterior surface)

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65
Q

Transmembrane protein orientation and topology

A

cytosolic segments always face the cytosol, ectoplasmic segments always face the opposite

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66
Q

What is something that many transmembrane proteins contain?

A

carbohydrate chains covalently linked to serine, threonine, or asparagine that face the ectoplasmic domain
attached to the glycerol or sphingosine backbone of glycolipids in the ectoplasmic leaflet

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67
Q

Antibodies for A blood

A

anti-B

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68
Q

Antibodies for B blood

A

anti-A

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69
Q

Antibodies for AB blood

A

none

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70
Q

Antibodies for O blood

A

anti-A and anti-B

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71
Q

What blood types can type A receive?

A

A and O

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72
Q

What blood types can type B receive?

A

B and O

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73
Q

What blood types can type AB receive?

A

All blood types

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74
Q

What blood types can type O receive?

A

O

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75
Q

Which blood type is the universal donor?

A

type O

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76
Q

How do detergents remove proteins from membranes?

A

they disrupt membranes by intercalating into phospholipid bilayers

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77
Q

What completely denatures proteins at high concentrations?

A

sodium dodecylsulfate (SDS)

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78
Q

What are non-ionic detergents used for?

A

extracting proteins in their folded and active form

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79
Q

What are the various ways membrane proteins associate with the bilayer?

A
  1. a single alpha helix
  2. multiple alpha helices
  3. a beta barrel
  4. anchored to cytosolic surface by an amphipathic alpha helix
  5. covalently attached lipid chain
  6. oligosaccharide linker
  7. non covalent interactions with other membrane proteins
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80
Q

When do cells synthesize new membranes?

A

the expansion of existing membranes

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81
Q

What roles do fatty acids play in cells?

A

they are a fuel source, are key components of phospholipids and sphingolipids, and anchor some proteins to the membrane

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82
Q

Where does synthesis of phospholipids take place?

A

ER

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83
Q

What starts synthesis of fatty acids?

A

formation of acetyl CoA via esterificaiton

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84
Q

What are fatty acids bound to, that allows for transportation through the cytosol?

A

fatty-acid binding proteins (FABPs) that act as chaperones

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85
Q

Where are fatty acids incorporate into phospholipids?

A

ER membrane

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86
Q

Process for fatty acid incorporation into phospholipids

A
  1. two fatty acids are esterified to the phosphorylated glycerol backbone forming phosphatidic acid
  2. phosphatase converts phosphatidic acid into diacylglycerol
  3. polar head group is transferred to the exposed hydroxyl group
  4. flippase proteins catalyze the movement of phospholipids from the cytosolic leaflet to the exoplasmic leaflet
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87
Q

How are sphingolipids synthesized in the ER?

A

coupling of palmitoyl group to serine, second fatty acyl group is added to form ceramide, which is sent to the Golgi

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88
Q

How are sphingolipids synthesized in the Golgi?

A

polar head group is added to ceramide making sphingomyelin, which is then transported out of the golgi

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89
Q

What is the backbone for sphingolipids?

A

ceramides

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90
Q

What are other functions of ceramides?

A

serve as signaling molecules for growth, endocytosis, stress responses, apoptosis, and proliferation

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91
Q

Where is cholesterol synthesized?

A

in the liver

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92
Q

How is cholesterol synthesized?

A
  1. HMG-CoA reductase converts HMG-CoA into mevalonate
  2. mevalonate is converted into IPP
  3. IPP is converted into cholesterol
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93
Q

What is atherosclerosis?

A

distortion of the artery’s wall, leading to blockage of blood flow

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94
Q

What are statins?

A

anti-atherosclerosis medication

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95
Q

How do statins work?

A

bind to HMG-CoA and inhibit its activity

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96
Q

What is the bilayer largely impermeable to?

A

water-soluble molecules and ions

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97
Q

What can cross the membrane by simple diffusion?

A

gases and small uncharged molecules (urea, ethanol)

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98
Q

A higher concentration gradient causes a faster…

A

rate of movement across bilayer

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99
Q

What is the first and rate limiting step of diffusion?

A

movement across hydrophobic core

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100
Q

If a substance carries a net charge, what influences movement across a membrane?

A

substances concentration gradient and the membrane potential

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101
Q

Transport of most molecules requires the assistance of what?

A

membrane proteins

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102
Q

All transport proteins are what?

A

transmembrane proteins, generally alpha helices

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103
Q

3 main classes of transport molecules

A

channels, transporters (carriers), ATP-powered pumps

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104
Q

3 types of channels

A

non-gated and gated

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105
Q

Non-gated channels

A

open at all times
ex. aquaporins

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106
Q

Gated channels

A

selective for the type of molecule they transfer

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107
Q

Describe channels

A

transport proteins that transport water, specific ions, or small molecules down concentration gradient without the use of energy

108
Q

What transports proteins slower than channels?

A

transporters (carriers)

109
Q

3 types of carriers

A

uriporters, symporters, antiporters

110
Q

Uniporters

A

transport single type of molecule

111
Q

Symporters

A

coupled transport of molecules in same direction

112
Q

Antiporters

A

coupled transport of molecules in different directions

113
Q

Describe ATP-powered pumps

A

use ATP hydrolysis for energy to move ions or small molecules against their concentration gradient

114
Q

What type of energy do cotransporters use and what is the process referred to as?

A

use energy stored in an electrochemical gradient, referred to as secondary active transport

115
Q

Alternating access model of channels

A

channels switch between open and closed state with NO conformational change
has high rates of transport

116
Q

Alternating access model of transporters and ATP-powered pumps

A

both undergo a cycle of conformational change which exposes a binding site in extracellular space and then changes again to expose cytosolic space, allowing the molecule in
has low rates of transport

117
Q

What give a uniporter maximum transport rate (Vmax)?

A

large concentration gradient across membrane and uniporter working at maximum rate

118
Q

What features distinguish uniport from simple diffusion?

A

-uniport moves substrates at a higher rate
-solubility is irrelevant
-there is limited number of uniport molecules
-transport is reversible

119
Q

What transports glucose in mammalian cells?

A

GLUT-1

120
Q

What are the two conformational states of GLUT-1 (alternating access model)?

A

glucose-binding site facing outside of cell or cytosol

121
Q

What GLUT has the highest affinity (Km) for glucose?

A

GLUT-1

122
Q

Where is GLUT-2?

A

in liver cells and insulin-secreting beta cells of the pancreas

123
Q

Where is GLUT-3?

A

in neuronal cells of brain
have high glucose affinity (low Km)

124
Q

Where is GLUT-4?

A

fat and muscle cells

125
Q

Where is GLUT-5?

A

intestinal epithelial cells

126
Q

What does GLUT-2 do?

A

has triggered activation

127
Q

What does GLUT-3 do?

A

ensures cells have a high and constant supply of glucose

128
Q

What does GLUT-4 do?

A

increases glucose uptake in response to insulin; unable to uptake glucose in absence of insulin

129
Q

What does GLUT-5 do?

A

has high specificity for fructose, transports it from intestinal lumen to inside cells

130
Q

What causes water to move across membranes?

A

osmotic pressure

131
Q

Hypotonic

A

concentration of solutes lower than in the cytosol, water moves into cell, cell swelling

132
Q

Hypertonic

A

concentration of solutes higher than in the cytosol, water moves out of the cell, cell shrinking

133
Q

Aquaporins increase what?

A

the water permeability of cellular membranes

134
Q

How many genes do humans have for aquaporins?

A

11

135
Q

Where is aquaporin 1?

A

in erythrocytes

136
Q

Where is aquaporin 2?

A

in kidney epithelial cells

137
Q

What regulates aquaporin 2?

A

vasopressin

138
Q

What aquaporin can transport molecules other than water?

A

aquaporin 3

139
Q

What are the 4 main classes of ATP-powered pumps?

A

P-class
V-class
F-class
ABC superfamily

140
Q

What are examples of P-class pumps?

A

Na/K ATPase pump
Ca ATPase pump

141
Q

What do P-class pumps have?

A

2 identical catalytic alpha subunits that each contain ATP binding sites

142
Q

Location of V-class pumps

A

animal lysosomal and eadosomal membranes

143
Q

Function of V-class pumps

A

responsible for maintaining a lower pH inside organelles
pumps protons from cytosolic to extoplasmic face against electrochemical gradient

144
Q

Where are F-class pumps?

A

bacterial plasma membranes, mitochondria, chloroplasts

145
Q

What are F-class pumps considered as?

A

reverse proton pumps

146
Q

What are the 4 core domains of ABC superfamily?

A

two transmembrane domains (T) that form a passageway and two cytosolic ATP binding (A) domains

147
Q

What maintains intracellular Na and K concentrations?

A

Na/K ATPase

148
Q

Na/K ATPase shares structural homology to what?

A

Ca pumps

149
Q

For every 1 ATP molecules hydrolyzed, Na/K ATPase moves…

A

3 Na out and 2 K in

150
Q

E1 conformation of Na/K pump

A

cytosolic sites have have affinity for Na and low affinity for K

151
Q

E2 conformation of Na/K pump

A

the 3 bound Na gain access to exoplasmic face, sites have low affinity to Na and high affinity to K

152
Q

Process for Na/K ATPase

A
  1. 3 Na out, 2 K in
  2. E1 conformation
  3. Phosphorylation and conformation change
  4. E2 conformation
  5. Phosphorylation and conformation changes
  6. E1 conformation, K released
153
Q

What are the 2 abundant proteins in the lumen of the sarcoplasmic reticulum?

A

calsequestrin and high-affinity Ca binding protein

154
Q

What regulates activity of Ca ATPase?

A

calmodulin

155
Q

E1 state of Ca ATPase

A

2 Ca binding sites facing cytosol

156
Q

E2 state of Ca ATPase

A

binding sites accessible to SR lumen

157
Q

Process for Ca ATPase pumps

A
  1. E1 state, low cytosolic Ca but Ca still binds
  2. conformational change, ATP hydrolysis
  3. E2 state
  4. Ca dissociates
  5. E2-E1 conformational change
158
Q

What do V-class H+ ATPases transport?

A

H+ only

159
Q

The movement of H+ is accompanied by…

A

the movement of an equal number of anions in the same direction and an equal number of cations in the opposite direction

160
Q

What do ABC proteins do?

A

use energy from ATP hydrolysis to export a wide variety of drugs and toxins from the cell

161
Q

Which ABC proteins can move a hydrophobic or amphipathic substrate from the inner leaflet to the outer leaflet?

A

ABCB1 and ABCG2

162
Q

Process of the Flippase model of ABC superfamily

A
  1. lipid tail of LLO binds to extracellular facing helix of flippase subunits
  2. exchange of ATP for ADP, dimer converts to an outward-open state
  3. hydrophilic oligosaccharide head of LLO enters positively charged pore of the transporter
  4. dimer returns to an inward-open conformation
  5. LLO tail dissociates
163
Q

ABC cystic fibrosis transmembrane regulator (CFTR) is a…not a…

A

chloride channel, not a pump

164
Q

What is protein targeting?

A

the delivery of newly synthesized proteins to their proper destinations

165
Q

Where does signal based targeting go?

A

targeting of a newly synthesized protein from the cytoplasm to an organelle

166
Q

Where does vesicle-based trafficking in the secretory pathway go?

A

transport of proteins from ER to a membrane-enclosed vesicle

167
Q

For membrane proteins, where does targeting lead?

A

to insertion in the bilayer

168
Q

For water-soluble proteins, where does targeting lead?

A

to translocation of protein across the membrane

169
Q

What is a microsome?

A

a fragment of ER and attached ribosomes

170
Q

Where does secretory protein synthesis begin?

A

on free ribosomes in the cytosol

171
Q

During protein synthesis, translation and translocation occur…

A

simultaneously

172
Q

How are proteins moved into membranes & organelles?

A

signal sequence, SRP, and SRP receptor docks the ribosome on an ER translocon & inserts the protein

173
Q

Secretory proteins are synthesized in association with what membrane?

A

ER membrane

174
Q

Process of co-translational translocation

A
  1. N-termial ER signal sequence emerges from ribosome
  2. SRP binds signal sequence & arrests protein synthesis
  3. SRP-nascent polypeptide chain-ribosome complex binds to SRP receptor in ER membrane
  4. GTP binds to SRP & its receptor
  5. translocation channel opens
  6. signal sequence goes to binding site next to central pore
  7. GTP hydrolyzed
  8. elongating polypeptide chain passes into ER lumen
  9. signal sequence is cleaved
  10. growing peptide chain continues through translocon into the ER, mRNA translated towards 3’ end
  11. translation stops, ribosome released
  12. translocon closes, nascent protein in ER lumen & folds
175
Q

Process of post-translational translocation

A
  1. N-terminal segment of protein enter ER lumen
  2. BiP and Sec63 complex provide driving force for unidirectional translocation
  3. BiP ATP hydrolysis happens, BiP-ADP has conformational change & promotes binding to exposed polypeptide chain
  4. BiP binding prevents backsliding of peptide through translocon
  5. random inward sliding
  6. BiP-ADP binding directs protein into ER
  7. BiP released from protein
  8. protein folds
176
Q

What uses post-translational translocation?

A

some yeast secretory proteins

177
Q

What are the 3 single-pass membrane proteins?

A

types 1, 2, 3

178
Q

Process of membrane insertion & orientation of type 1 transmembrane proteins

A
  1. translocation initiation & SS cleavage
  2. peptide elongates
  3. stop transfer anchor sequence enters translocon
  4. prevention of chain moving further into lumen
  5. stop transfer anchor sequence moves laterally
  6. translocon closes
  7. synthesis continues until stop codon
  8. nascent protein diffuses into ER membrane
179
Q

Process of membrane insertion & orientation of type 2 transmembrane proteins

A
  1. SRP binds to internal signal-anchor sequence & interacts with SRP receptor; positively charged AAs on N terminal side orient chain
  2. chain elongation
  3. internal signal-anchor sequence moves laterally
  4. completion of protein synthesis
  5. peptide C-terminus released into ER lumen
180
Q

Process of membrane insertion & orientation of type 3 transmembrane proteins

A
  1. SRP binds tot internal signal-anchor sequence & interacts with SRP receptor; positively charged AAs on C-terminal side orient chain
  2. C-terminal elongation
  3. ribosomal subunits released
181
Q

Process of insertions of tail-anchored proteins

A
  1. Sgt2, Get4 and 5 take C-terminal tail of nascent protein & transfer it to Get3-ATP
  2. Get2-ATP-nascnet protein complex docks onto Get1/Get2 receptor on ER membrane
  3. Get3 ATP hydrolysis releases ADP and protein C-terminal tail into Get1/Get2 receptor, which releases tail-anchor sequence into ER membrane
    4.
182
Q

What determines orientation of type 1 proteins?

A

N-terminal signal sequence & STA sequence

183
Q

What determines orientation of type 2 proteins?

A

high density of + charged AAs on N-terminal side of SA sequence

184
Q

What determines orientation of type 3 proteins?

A

high density of + charged AAs on C-terminal side of
SA sequence

185
Q

What determines orientation of type 4 A proteins?

A

N-terminus in the cytosol & alternating type 2 SA & STA sequences

186
Q

What determines orientation of type 4 B proteins?

A

N-terminus in the ER lumen & type 3 SA sequence followed by type 2 SA & STA sequences

187
Q

What proteins are considered multiples proteins?

A

Type 4

188
Q

If multipass proteins have an even number of alpha helices, how will its N and C terminus be oriented?

A

towards the same side of the membrane

189
Q

If a multipass protein has an odd number of alpha helices, how will its N and C terminus be oriented?

A

in opposite orientations

190
Q

What 4 principal modifications do secretory proteins go through before they reach their final destinations?

A
  1. addition & processing of carbohydrates in ER & Golgi complex
  2. formation of disulfide bonds in the ER
  3. proper folding of chains in the ER
  4. proteolytic cleavages in ER, Golgi, and secretory vesicles
191
Q

What are glycoproteins?

A

proteins with attached carbohydrates

192
Q

O-linked oligosaccharides

A

have carbohydrate chains on hydroxyl side

193
Q

N-linked oligosaccharides

A

have carbohydrate chains on amide side

194
Q

What can promote folding and stability of glycoproteins?

A

oligosaccharide side chains

195
Q

What does protein disulfide isomerase (PDI) do?

A

forms & rearranges protein cysteine disulfide bonds

196
Q

Where are disulfide bonds formed and rearranged?

A

ER lumen

197
Q

What facilitate folding & assembly of proteins?

A

chaperones & other ER proteins

198
Q

What does peptide-prolyl isomerase (PPI) do?

A

accelerates rotation above peptide-prolyl bonds in unfolded segments of a polypeptide

199
Q

What is the unfolded protein response?

A
  1. unfolded proteins accumulate in the ER lumen
  2. bind to Bip
  3. release Ire1
  4. Ire1 cuts unspoiled mRNA precursor making Hac1
  5. 2 Hac1 exons join
  6. Hac 1 translated into Hac1 protein
  7. transcription of chaperone encoding genes
200
Q

Where are unassembled or misfiled proteins transported to for degradation?

A

cytosol

201
Q

Process of protein import into the mitochondrial matrix

A
  1. precursor proteins are in unfolded state
  2. MTS binds to outer membrane receptor
  3. MTS inserted into TOM
  4. translocating protein inserted into TIM
  5. protein translocates through TIM
  6. MTS removed
  7. Hsp70 releases newly imported protein
  8. protein folds into its active form
202
Q

What are the major structural features of the nuclear pore complex model?

A

membrane, structural, and FG- nucleoporins

203
Q

FG nucleoporins form what kind of matrix?

A

gel-like

204
Q

What are the nuclear proteins?

A

histones, transcription factors, DNA & RNA polymerases

205
Q

What does the nuclear localization signal (NLS) do?

A

targets protein for import through nuclear pores

206
Q

Process of NLS protein import in cytoplasm

A
  1. importin binds to NLS to form importin cargo complex
  2. importin cargo complex diffuses through
207
Q

Process of NLS protein import in nucleoplasm

A
  1. Ran-GDP gets activated by GEF
  2. Ran-GTP forms & binds to importin causing conformational change that releases NLS-cargo protein
208
Q

What does ran-dependent mechanism use for nuclear export of proteins?

A

NES

209
Q

What does ran-independent mechanism use for nuclear export of proteins?

A

NXF1 or NXT1

210
Q

The composition of the plasma membrane is determined by what two pathways?

A

secretory and endocytic pathways

211
Q

Process of exocytosis

A

membranes & proteins are delivered to the membrane by exocytosis of coated vesicles that bud from the Golgi

212
Q

Process of endocytosis

A

membranes & proteins are removed from the plasma membrane & coated vesicles bud from the membrane into the cytoplasm

213
Q

Where does the first stage of the secretory pathway take place?

A

rough ER

214
Q

How do cargo proteins get transported from the ER to the Golgi?

A

anterograde (forward-moving) transport vesicles

215
Q

How do cargo proteins get returned back to the ER?

A

retrograde (backward-moving) transport vesicles

216
Q

What is a cisterna?

A

flattened membrane bound compartments that hold liquid
made from fusion of transport vesicles

217
Q

What is constitutive secretion?

A

proteins that are secreted continuously

218
Q

What is regulated secretion?

A

proteins that are stored inside secretory granules that are not released until a signal for exocytosis

219
Q

What is vesicle budding driven by?

A

polymerization of coat proteins

220
Q

What is vesicle budding regulated by?

A

GTP binding proteins

221
Q

What is cargo gathering?

A

interactions between cytosolic parts of integral membrane proteins & vesicle coat

222
Q

What are 3 types of coated vesicles?

A

COPI, COPII, Clathrin

223
Q

What do COPII vesicles do?

A

transport proteins from ER to Golgi

224
Q

What do COPI vesicles do?

A

transport proteins in retrograde direction

225
Q

What does Clathrin do?

A

transport proteins from cell surface to late endosomes

226
Q

What does Sar1 do?

A

assembles & disassembles the COPII coat

227
Q

What causes COPII disassembly?

A

Sar1-GDP being released from the vesicle

228
Q

What do Rab GTPases do?

A

control docking of vesicles on target membrane

229
Q

What do SNARE proteins do?

A

form stable coiled-coil complexes

230
Q

Where is v-SNARE?

A

on target vesicle

231
Q

Where is t-SNARE?

A

on target membrane

232
Q

Process for docking & fusion of transport vesicles with their target membranes

A
  1. vesicle docking
  2. assembly of SNARE complexes
  3. membrane fusion
  4. disassembly of SNARE complexes
233
Q

What is anterograde transport mediated by?

A

COPII transport vesicles

234
Q

Mutation in what protein causes cystic fibrosis?

A

CTFR

235
Q

What is retrograde transport mediated by?

A

COPI transport vesicles

236
Q

What is the main function of KDEL receptor in retrograde transport?

A

to retrieve proteins containing the KDEL sorting signal to bring them back to the ER

237
Q

How to proteins advance through Golgi?

A

by cisternal maturation

238
Q

What is the role of adapter proteins (AP) complex?

A

transport from trans-golgi network directly to lysosome

239
Q

What is the role of clathrin-coated AP complex?

A

transport from trans-golgi network to late endosome to lysosome

240
Q

What is the role of constitutive and regulated secretory vesicles?

A

transport from trans-golgi network to cell surface

241
Q

Clathrin molecules have what kind of shape?

A

three-limbed

242
Q

What is dynamin essential for?

A

release of complete vesicle

243
Q

What 3 proteins do regulated secretory vesicles contain?

A

chromogranin A & B, secretogranin II

244
Q

Where can proteolytic maturation occur?

A

vesicles carrying protein, late endosome, in lysosome

245
Q

What are the 2 types of endocytosis?

A

pinocytosis & receptor-mediated

246
Q

What is pinocytosis?

A

nonspecific take up of small droplets of extracellular fluid & anything dissolved in it

247
Q

What is receptor mediated endocytosis?

A

specific receptor on cell surfaces binds tightly to what is coming in, becomes a transport vesicle

248
Q

2 types of receptor-bound ligands used for receptor-mediated endocytosis

A

LDLR & transferrin

249
Q

How are lipids taken up from the blood to form lipoprotein complexes?

A
  1. LDLR binds LDL
  2. clathrin-coated pits pinch off
  3. vesicle sheds coat
  4. LDL particle released
  5. late endosome fuses with lysosome
250
Q

Mutations in LDLR can cause what hereditary disease?

A

hypercholesterolemia

251
Q

What is the main function of the lysosome?

A

to degrade extracellular material taken up by the cell

252
Q

How are things delivered to the lysosome for degradation?

A
  1. vesicles fuse with the late endosome
  2. early endosomes fuse with late endosome
  3. proteins targeted for degredation bud into the interior of the late endosome forming multivesicular endosome
  4. multi vesicular endosome fuses with lysosome
253
Q

Endocrine signaling

A

messengers reach target cells through blood stream
ex. hormones

254
Q

Paracrine siganling

A

messengers travel short distance
ex. neurotransmitter

255
Q

Autocrine signaling

A

cell has receptors on its surface that respond to messenger

256
Q

What is signal transduction?

A

any process where cell converts one kind of stimulus to another

257
Q

What carries out signal transduction?

A

enzymes

258
Q

What activated signal transduction?

A

second messengers

259
Q

3 main types of cell surface receptor proteins

A

GPCR, ion channel receptors, receptor tyrosine kinases

260
Q

Examples of second messengers

A

cAMP and Ca2+

261
Q

What are second messengers?

A

water soluble molecules or ions that spread throughout cell & activate responses

262
Q

Process for activation of CREB

A
  1. receptor stimulation
  2. activation of PKA
  3. PKA subunits go to nucleus
  4. subunits phosphorylate & activate CREB
263
Q

E1 state of Ca2+ ATPase pumps

A

two Ca binding sites, high affinity for Ca

264
Q

E2 state of Ca2+ ATPase pumps

A

binding sites open to SR (after conformational change), Ca2+ dissociates

265
Q

What can receptor tyrosine kinases (RTK) do?

A

simultaneously activate multiple signal transduction pathways

266
Q

What do RTKs catalyze?

A

the transfer of a phosphate from ATP to tyrosine residues

267
Q

What do ion channel receptors act like?

A

a gate

BMS 521 (3 decks)

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