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MCB 2210 Cellular Biology > BLOCK 1 > Flashcards

BLOCK 1 Flashcards

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1
Q

prokaryotes

A

bacteria and archaea; lack a nucleus and internal membranes

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2
Q

eurkaryotes

A

multicellular animals; plants and fungi, unicellular protists; has nucleus and extensive internal membrane system

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3
Q

cell theory

A
  1. all living things are made of one or more cells
  2. the cell is the structural and functional unit of all living things
  3. all cells come from pre-existing cells by division
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4
Q

modern cell theory

A
  1. cells contain hereditary information which is passed from cell to cell during cell division
  2. all cells are basically the same in chemical composition
  3. all energy flow (metabolism and biochemistry) of life occurs within cells
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5
Q

the central dogma

A

activation
transcription
processing
translation

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6
Q

proteome

A

read gene sequences to predict the complement of proteins

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7
Q

differential gene expression

A

determines which genes are expressed and at what levels

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8
Q

transcription factors

A

proteins that interact with specific DNA regulatory sequences associated with genes to modulate transcription by recruiting RNA polymerases

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9
Q

transcriptome

A

genes being transcribed

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10
Q

epigenetics

A

heritable changes in the genetic potential of a cell without changes to the underlying DNA sequence

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11
Q

chromatin modifications

A

epigenetic changes that regulate the access to regulatory sequences and thus regulate transcription (methylating cytosines prevents accessibility to gene)

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12
Q

noncoding RNAs

A

regulate/ control mRNAs

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13
Q

microRNAs (miRNAs)

A

nonprotein coding; folded and cleaved into siRNAs

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14
Q

long non-coding RNAs

A

processed into siRNAs

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15
Q

small interfering RNAs (siRNAs)

A

destroys and inhibits complementary mRNAs by RNAi

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16
Q

RNA-induced silencing complex (RISC)

A

inhibits or destroys targeted RNA

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17
Q

primary cells

A

non-cancerous, non-transformed

some divide, some already differentiated
can be isolated or cultured

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18
Q

challenge of primary cells

A

not alive forever

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19
Q

transformed cells

A

cancerous cells

can be grown in culture; some model basic cell functions, others retain specialized functions

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20
Q

stem cells

A

can be isolated or induced

embryonic stem cells that have self-renew capacity, not differentiated but capacity to do so is there

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21
Q

light microscopy

A

limited in contrast, magnification, resolving power

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22
Q

why is contrast poor in light microscopy?

A

cells are transparent so they don’t absorb light and therefore contrast is poor

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23
Q

techniques for enhancing contrast in light microscopy

A

modulate phase of light using optical tools

modulate contrast of specimen

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24
Q

enhancing contrast: modulating phase of light using optical tools

A 
phase contrast (strict contrast)
differential interference contrast (DIC) --> 3D looking
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25
Q

magnification

A

the amount the initial image is blown up –> dependent on lenses used

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26
Q

resolution

A

how far apart two objects have to be to be seen as two separate objects

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27
Q

what determines resolution?

A

the wavelength of light used (shorter = better resolution)

the properties of lenses used (NA, width of light cone the objective gathers)

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28
Q

what is the resolution of a conventional light microscope?

A

1/2 the wavelength of light being used

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29
Q

airy patterns

A

when light interacts with a specimen, the light gets defracted into a pattern

airy disk diameter is determined by light WL (smaller WV = smaller diameter)

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30
Q

fluorescence microscopy

A

improves contrast and allows specific cellular structures to be labeled

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31
Q

fluorescence

A

when a molecule absorbs light of one wavelength and then re-emits it as a longer wavelength

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32
Q

fluorophores (fluors)

A

labels specific structures because is linked to various chemicals

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33
Q

fluorescence microscopy process

A

molecules are treated with light of a certain energy; the molecule will absorb it, kick out a photon with a certain WL, some energy will be lost; and a longer WL is transmitted (red shift)

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34
Q

fluorescent proteins

A

genetically encoded fluorescence markers that can be fused to proteins of interest at the DNA sequence level (allows live imaging)

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35
Q

CMV promoter

A

driving expression of a GFP-tubulin fusion protein in all cells

induces transfection, recruits transcription factors

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36
Q

tissue specific promoters

A

drive tissue-specific protein expression

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37
Q

immuocytochemistry

A

immunolabeling; visualizes proteins in cells

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38
Q

immunocytochemistry process

A
  1. fix: fixatives react, cross link, and freeze everything in the cell to nearby molecules
  2. permeabilize: detergent perforates membrane so antibodies can enter
  3. antibodies bind to target
  4. a fluorescent “secondary antibody” binds to primary antibody if the primary is not directly labeled
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39
Q

immunoblotting (western blotting)

A

allows us to take samples of a cell and figure out if a protein is present in the cells

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40
Q

immunoblotting process

A

electrophoresis and transfer; antibody detection; chromogenic detection

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41
Q

immunoisolation / immunoprecipitation

A

antibody specifically binds to a particular protein and the antigen is precipitated. process can be used to isolate and concentrate a particular protein from a sample

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42
Q

antibodies

A

immune proteins that bind to specific proteins; made by B cells (2 heavy and 2 light chains)

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43
Q

epitope

A

specific 8-12 amino acid sequence

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44
Q

monoclonal antibodies

A

made by isolating and cloning a single antibody-producing cell and thus recognize a single epitope; all antibodies produced are identical

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45
Q

polyclonal antibodies

A

mxiture of different antibodies produced by the host animals B-cells against various epitopes of the target protein and isolated from blood serum

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46
Q

transfection

A

to cause a foreign protein to be expressed in a cell

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47
Q

what kinds of things can you express in a cell with transfection?

A
  • GFP-tagged versions of molecules
  • proteins that aren’t normally present in the cell
  • mutant proteins that are constitutively active (enzymes; mutate to make always active)
  • mutant proteins that are dominant negative (proteins that don’t function right and block the function of the cell’s own version of the molecule
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48
Q

transient transfection

A

expression from plasmid

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49
Q

stable transfection

A

DNA integrates into genome; heritable

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50
Q

RNA interference (RNAi) purposes

A
  • protects against viral RNA

- regulates stability of cell’s own mRNAs via miRNAs or siRNAs

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51
Q

RNAi process

A

miRNA and siRNA direct enzyme complexes to degrade mRNA molecules and prevent translation when transfected into cells

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52
Q

laser-scanning confocal microscopy

A

uses pinholes to deblur by eliminating light from upper and lower planes (thin, focused plane of light)

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53
Q

digital deconvolution

A

uses computational methods to deblur; predicts peak intensity of brightness

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54
Q

super resolution fluorescence

A

PALM
STORM

allows images to be taken with a higher resolution than the one imposed by the diffraction limit

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55
Q

STORM (stochastic optical reconstruction microscopy)

A

lasers are used to photo-activate fluorphores that quickly switch back off; repeating allows the center of the light spot to be calculated and mapped onto a digital image

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56
Q

electron microscopy

A

shorter wavelength than light - higher resolution (.004nm instead of 400-500nm)

TEM
SEM

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57
Q

TEM

A

transmission electron microscope

images electrons that pass through a specimen

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58
Q

TEM process

A

shining beam of electrons at a thin stained sample; electrons get deflected by metal bound to the structures of cell and a detector picks up the deflected electrons

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59
Q

resolution of TEM

A

.1-.2nm with magnetic lenses

.002nm with optical lens

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60
Q

SEM

A

scanning electron microscope

images electrons scattered by an intact object; depth of focus gives 3D image quality

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61
Q

SEM resolution

A

5 nm

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62
Q

SEM process

A

coat sample in metal stain; electrons bounce off to deflectors and image is created from that

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63
Q

SEM use

A

used to look at surfaces of structures

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64
Q

SEM use

A

used to look at surfaces of structures

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65
Q

electron microscopy process

A

samples must be dehydrated; imaging is done in a vacuum and water creates noise - must be fixed and stained with heavy metals which leaves a scaffold of what was the cellular material

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66
Q

immunoelectron microscopy

A

labeling structures in electron microscopy

attach dense particles (gold beads) to antibodies to make them visible; gold beads are electron dense, antibody sticks to protein of interest in the cell –> electrons will scatter upon hitting the bead and show where proteins are

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67
Q

centrifugation

A

differential centrifugation

gradient centrifugation

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68
Q

differential centrifugation

A

components separate depending on their densities; the less dense a material, the longer or faster it needs to spin to separate

lipid rich structures are not dense so it is difficult to separate them

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69
Q

gradient centrifugation

A

fine tunes differential centrifugation

many tubes of solution (let’s say sucrose) are made with different concentrations which have different (known) densities. A concentration gradient with the sucrose solutions is made –> sample from differential centrifugation is added and components will separate and settle out on the level where their density matches the density of the sucrose

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70
Q

membrane functions

A

separate compartments/ selectively permeable
provide scaffold for biochem activities (energy transduction)
mediate some kinds of cell-cell interactions
key element of signal transduction pathways

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71
Q

lipids

A

phospholipids, glycolipids, sterols

amphipathic

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72
Q

phospholipids

A

all have phosphate linkage to a head group and 2 fatty acid tails

phosphyglycerides, sphingomyelin

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73
Q

phosphoglycerides

A

major component of most membranes

two fatty acid chains linked to a glycerol with glycerol phosphate on head group

one saturated (straight) chain and one unsaturated (kinked)

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74
Q

sphingomyelin

A

sphingosine amino group (instead of glycerol) links to phosphate head

two saturated fatty acid chains

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75
Q

saturated chain

A

straight

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76
Q

unsaturated chain

A

kinked

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77
Q

glycolipids

A

sphingosine amino group links directly to a sugar head group (no phosphate)

two saturated tails

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78
Q

sterols

A

four ring hydrocarbons, cholesterol can increase or decrease membrane fluidity depending on conditions

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79
Q

structures formed from lipids in water

A

micelles

bilayers

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80
Q

micelles

A

small spheres with tails pointed in

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81
Q

bilayers

A

two layers of lipids with tails pointed toward each other

spontaneously forms; close upon themselves to make a continuous surface interacting with water

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82
Q

phosphatidylcholine

A

unsaturated tails provide a thinner membrane

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83
Q

sphingomyelin

A

saturated tails provide a thicker membrane

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84
Q

cholesterol

A

inserts itself into membranes and can affect properties

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85
Q

cholesterol + phosphatidylcholine

A

straightens kinked tails, increases thickness

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86
Q

cholesterol + sphingomyelin

A

doesn’t affect thickness

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87
Q

properties that can affect a membrane structure

A

size of head groups, tail shapes

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88
Q

lateral shifting / lateral diffusion (membrane)

A

a lipid’s ability to drift within a leaflet on the same plane

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89
Q

flexion / rotation

A

bending of tails from thermal energy (common)

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90
Q

transverse flip-flop

A

when lipids on opposite planes of a leaflet switch places (rare, not natural since hydrophobic heads need to come in contact with water –> requires energy)

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91
Q

how to determine lateral mobility of lipids

A

microscopy –> fluorescence recovery after photobleaching (FRAP)

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92
Q

FRAP

A

determines lateral mobility of lipids; phospholipids are labeled with a fluorescent probe; a bright laser is shined on a small spot of membrane to bleach the fluorescence on those lipids; the time it takes for other fluorescent lipids to diffuse into the bleached region demonstrates lateral mobility

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93
Q

leaflet

A

lipids are synthesized in the ER and inserted into one or the other faces of the bilayer

not randomly distributed into the plane

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94
Q

flipases

A

membrane proteins that flip-flop lipids back to their normal sides to maintain asymmetry

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95
Q

sphingolipids in the membrane

A

tend to cluster relative to other membrane lipids

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96
Q

microdomains

A

created from clustering of lipids in membrane –> lipid rafts

97
Q

lipid rafts

A

regions of membrane with clustered lipids that serve structural and signaling properties

98
Q

membrane protein functions

A 
selective permeability
signal transduction
biochemical reactions
cell-cell interactions
membrane properties
99
Q

roles of proteins

A

enzymatic
structural
regulatory

100
Q

protein structure: primary

A

sequence of amino acids, determined directly from RNA sequence

linked by peptide bonds

side chain drives protein structure and function

101
Q

N-terminus

A

start of amino acid sequence; amino group is exposed

102
Q

C-terminus

A

end of amino acids sequence; carboxyl group is exposed

103
Q

protein structure: secondary

A

emerges from amino acid sequence (primary structure)

hydrogen bonding of peptide backbone causes AAs to fold into a pattern

alpha helix; beta pleated sheet

104
Q

protein structure: tertiary

A

3D FOLDING due to side chain interactions (hydrogen bonds, hydrophobic interactions, ionic interactions etc)

covalent disulfide bonds

105
Q

translation

A

ribosomes translate mRNAs into proteins by driving sequential formation of peptide bonds between carboxyl of one AA and amino of another

N-terminal exits ribosome first

106
Q

protein folding

A

can occur co-translationally

many ways to fold a protein but only one right way for a specific function

107
Q

chaperons and chaperonins

A

proteins that bind during or after synthesis to aid in proper folding

108
Q

HSP70

A

major chaperone

take proteins and hydrolyzes ATP to conformationally change chaperone protein and in turn folds the protein –> upon rebinding to ATP, chaperone releases folded protein

109
Q

chaperonins

A

help protein folding more than chaperone – larger complexes

110
Q

how to test if a protein needs a chaperone

A

isolate protein, apply heat to denature protein, if protein reforms and regains function upon cooling, protein doesn’t need chaperone

111
Q

disulfide bonds

A

covalent bonds between two cysteine amino acids in tert structure

112
Q

cysteine amino acid

A

side chains have sulfur in them –> under oxidizing conditions, will form disulfide bond which stabilize structures

113
Q

disulfide bonds: do they form in the cytoplasm?

A

No - cytoplasm is not an oxidizing environment

114
Q

oligosaccharides

A

large chain of sugars covalently attached to some amino acids that influence function

common in secreted proteins and membrane proteins (with ECM portion)

used as tags to mark the state of protein folding

115
Q

membrane glycoproteins

A

oriented so that the carbohydrate chains face the EX domain

116
Q

glycosylated proteins

A

processing in the ER and golgi does this to membrane and secreted proteins

117
Q

functional domains

A

combination of helices and sheets can fold into a functional domain that acts as a unit but is still only part of a protein

118
Q

functions of functional domains

A

ATP binding sites (myosin motor)

calcium binding sites

enzyme activity of a particular sort

regulation via interactions with another protein

119
Q

domain shuffling

A

new proteins can be formed by putting together new combinations of domains

120
Q

mammalian PLC

A

composed of functional domains found in other proteins (PH domains, EF-hand domains, X,Y domains, C2 domains)

121
Q

PH domains

A

lipids

122
Q

EF hand domains

A

Calcium

123
Q

XY domains

A

cleaving

124
Q

protein structure: quaternary

A

formed by the interaction between two or more proteins (subunits) that form a protein complex

125
Q

homodimer

A

quat structure; complex is composed of two identical subunits

126
Q

heterodimer

A

quat structure; if complex is composed of two different polypeptides

127
Q

quaternary structure is determined by…

A

hydrogen bonds, hydrophobic interactions, ionic interactions, polar interactions, van der Waals interactions, covalent-disulfide bonds

128
Q

affinity

A

protein binding - proteins with longer lasting associations, due to more non-covalent interactions have a higher affinity for each other

129
Q

on rate

A

dependent on starting material concentrations; determines how often they are likely to encounter each other in the first place

130
Q

on rate is dependent on

A

rate of diffusion, size of molecules, whether there is a favored orientation required for binding

131
Q

off rate

A

dependent on the Koff rate constant

132
Q

Koff rate constant

A

depends on the sum of the forces that will hold A and B together

133
Q

what truly determines the affinity of a reaction?

A

Koff rate constant

134
Q

higher affinity reaction

A

higher concentration of complexes at equilibrium

135
Q

Kd

A

equilibrium dissociation constant

136
Q

smaller Kd

A

higher affinity, smaller Koff

137
Q

larger Kd

A

lower affinity, larger Koff

138
Q

classes of membrane proteins

A

integral membrane proteins, lipid anchored proteins, peripheral membrane proteins

139
Q

integral membrane proteins

A

tightly associated with lipid bilayer

amino acids interact directly with the lipid portion

transmembrane proteins span the bilayer one or more times while others associate with only one leaflet

140
Q

lipid anchored proteins

A

covalent addition of a lipid to a protein anchors the protein to the membrane

some can cycle between membrane-bound and soluble forms

141
Q

lipid anchored proteins: fatty acids

A

added to attach proteins to the inner leaflet

142
Q

lipid anchored proteins: glycophosphatidylinositol (GPI)

A

are added to attach proteins to the outer leaflet

143
Q

peripheral membrane proteins

A

indirectly attached to the membrane via interactions with other membrane proteins, not lipids – localized

144
Q

immunolocalization

A

using immunofluorescence or immuno-EM to immunilocalize the protein to the membrane vs. the cytosol

(antibodies with fluorescent tag)

145
Q

process of immunolocalization

A

A) purify membrane and determine which proteins are present

  1. break cells by homogenization
  2. membranes have different density than other molecules so can be separated with sucrose gradient centrifugation
  3. different membranes of the cell have different compositions so can be separated from each other
  4. special detergents can be used to dissolve the membranes but keep the membrane protein active for immunoblotting or biochem. assay

B) purify the protein and show that association with membrane lipids is required for its function (proteases)

146
Q

proteases

A

cleave or digest accessible protein regions and can be used to deduce the topology of a protein in the membrane

147
Q

digestive proteases

A

break down the protein into many small, non-functional, peptide fragments and amino acids

trypsin

148
Q

cleaving proteins

A

cleave proteins at a specific sequence, thus generating larger, intact, potentially functional fragments

149
Q

transmembrane protein region structure

A

proteins are hydrophobic or amphipathic alpha helices

150
Q

single pass transmembrane protein

A

cross the bilayer once; one helix

151
Q

multipass transmembrane protein

A

crosses the bilayer 2 or more times; 2+ helices

152
Q

what is the length of an alpha helix needed to cross the membrane?

A

20-30 amino acids (~4nm)

different lipid composition gives rise to different bilayer thickness, so the length of a membrane protein’s hydrophobic alpha helix will influence what kind of lipid composition the protein “wants” to be in

153
Q

hydrophobic alpha helices

A

favorably interact with the inner hydrophobic region of the membrane

typical of single pass transmembrane proteins or isolated transmembrane domains

154
Q

multiple amphipathic alpha helices

A

can associate in the membrane to form water filled channels or pores

155
Q

what can associate in the membrane to form water filled channels or pores?

A

amphipathic alpha helices

156
Q

single amphipathic alpha helices

A

can also allow a protein to associate with one leaflet of the bilayer

157
Q

beta barrel

A

beta sheets can interact with membranes –> nonpolar on one side, polar on the other and rolled into a barrel –> forms a pore through the membrane

158
Q

can a protein leave the membrane once inserted?

A

no - too much energy is required to tear the hydrophobic region of the hydrophobic layer

159
Q

can the topology of a protein change once inserted into the membrane?

A

no - if it is made with X transmembrane domains, it will stay that way

160
Q

can the conformation of a protein change once inserted into the membrane?

A

Yes - shape changes allow proteins to pass signals from outside or inside

161
Q

can proteins move laterally within the membrane?

A

some, but not all

162
Q

fluid mosaic model of membranes

A

the lipid bilayer is a flexible 2D sheet in which membranes float in

163
Q

membrane domains

A

proteins that are restricted in their location to a particular region of the membrane; may be evenly distributed while others are restricted

can be restricted in one type of membrane and not another

164
Q

mechanisms to non-randomly distribute proteins

A

link them to other membrane proteins
link them to outside molecules
link them to inside molecules
prevent their diffusion to parts of the membrane

165
Q

methods to measure membrane protein mobility

A

Cell fusion

FRAP of fluorescently labeled protein

single particle tracking

166
Q

cell fusion

A

proteins of one cell labeled with red dye

proteins of a second labeled with green

fuse the membrane of two cells to form heterokaryon

watch two dyes –> overtime will mix

167
Q

FRAP of fluorescently labeled protein

A

connect protein to fluorescent tag and transfect it into cell with bleach

if fluorescence recovers, proteins are mobile

168
Q

single particle tracking

A

attach visible tracker to desired membrane protein (gold beads attached to antibodies) to trace movement of protein

169
Q

lipid rafts

A

made of cholesterol, sphingolipids, proteins

includes different proteins than non-raft areas

longer helix not happy in thinner bilayer

ex: GPI linked proteins

170
Q

transport proteins

A

enzymes that catalyze movement of substances across the membrane

171
Q

passive transport

A

facilitated diffusion

allows net movement down a gradient with ion channels and uniporters

172
Q

active transport

A

moves molecules against a gradient requiring energy with ATP pumps, symporters, and antiporters

173
Q

carriers

A

specific, initially rapid and maxes out, largely conformational, high affinity interaction

174
Q

passive transport domains

A

carriers, channels

175
Q

channels

A

small conformational changes, low affinity interaction

176
Q

kinetics of transport: carrier-mediated

A

transport peaks on carrier-mediated transport when binding sites are saturated due to high affinity interactions

177
Q

hypotonic

A

net water in, swelling cell

178
Q

hypertonic

A

net water out, cell shrinks

179
Q

isotonic

A

no net flow; when the total number of particles in and out are equal, the osmolarity is the same on both sides

180
Q

uncharged molecular movement

A

move on concentration gradients

181
Q

charged molecule movement

A

move on electrochemical gradient

182
Q

what determines Vm?

A

conductances for multiple ions; will be closer to Eion for the ion with greatest conductance

183
Q

ion channels

A

multipass transmembrane proteins form a pore

bidirectional down a gradient

ion specific, fast

regulated by gating mechanisms

184
Q

voltage gated K+ channel

A

tetramer with multiple membrane domains

N + C termini are intracellular

opened by depolarization, selective for K+

185
Q

ion selectivity filter for K+ channel

A

ions have hydration shell - Na+ is too small for this selectivity filter; opening the channel requires a small change in conformation

186
Q

patch clamping

A

flux through ion channels is so fast that currents flowing through a single channel can be recorded

187
Q

uniporters

A

multipass transmembrane domains that act as an enzyme

substrate binding induces reversible conformational change

functionally bidirectional but down an electrochemical gradient

slower than channels

188
Q

GLUT transporters

A

uniporter; 12 transmembrane domains (N+C intracellular)

mM affinity for glucose

GLUT4 is stored in vesicles and inserted into muscle or fat cell membrane in response to insulin; regulated secretion to put protein on membrane surface

189
Q

ATP pumps

A

hydrolyze ATP and use energy to move 1 or more molecules across the membrane

190
Q

P type pumps

A

become phosphorylated (Na+/K+ ATPase, K+/H+ ATPase)

191
Q

V type pumps

A

vesicular H+ ATPases

no phosphorylation, pumps H+ into membrane compartments

acidification of endocytic vessels, lysosomes, golgi

192
Q

Na+/K+ ATPase

A

3Na+ in / 2K+ out both against their gradients
binding of Na+ changes shape allowing for ATP to bind (autocatalytic reaction), phosphorylation changes shape and allows Na+ to be released; K+ binding allows release of Pi group

193
Q

ouabain

A

plant compound that blocks Na+/K+ ATPase and prevents reestablishment of gradients

194
Q

K+/H+ ATPase

A

P type; stomach acidification

195
Q

Ca2+ ATPase

A

P type; pumps Ca2+ out of cell or into ER

196
Q

ABC

A

ATP binding cassette

no phosphorylation; cancer cells overproduce this channel type and pump drugs out of cell –> become resistant

cystic fibrosis gene product is an ABC for Cl- in lungs, sweat glands, kidneys

197
Q

symporter / cotransporters

A

both molecules move in the same direction; uses energy from molecule moving down its existing gradient to move a second up its gradient

large conformational changes

198
Q

Na/glucose symporter

A

2 Na out, 1 glucose in; concentrates glucose from intestine into epithelial cells; works against glucose gradient using the Na+ gradient

can accumulate glucose 30k fold

199
Q

antiporters

A

two ions moving in two directions, one along its gradient

carrier mediated and pronounced conformational changes

200
Q

glucose absorption in the intestine

A

Na+/glucose transporter
facilitated glucose transporter
Na+/K+ ATPase

201
Q

nerve cell signaling

A

action potentials ya ya ya ya ya ya info is in frequency of it ya know

202
Q

initiation AP

A

nerves, mechanical, sensory

203
Q

gating mechanisms

A

voltage, ligand, mechanical

204
Q

cardiac

A

u kno dis

205
Q

signal transduction: hydrophobic signals

A

can cross membrane directly

steroid hormones, NO, CO

206
Q

steroid hormones

A

receptors in cytoplasm or nucleus

207
Q

NO/ CO

A

dissolved gas regulates many pathways and can enter cell easily

208
Q

signal transduction: hydrophilic signals

A

cannot cross the membrane; instead needs to indirectly signal across the membrane by binding to transmembrane proteins

209
Q

types of signals

A

chemical messenger signaling, contact-dependent signaling

210
Q

chemical messenger signaling

A

autocrine
paracrine
endocrine

211
Q

autocrine signaling

A

cell surface receptor binds a molecule secreted by itself

212
Q

paracrine signaling

A

nearby cell secretion and binding

213
Q

endocrine signaling

A

hormone secretion into blood onto distant target cells

214
Q

contact-dependent signaling

A

cell surface receptor binds a signal on the surface of another or to ECM

215
Q

signal transduction scheme

A

signal (first messenger) –> membrane receptor -=-> transducer –> second messengers –> effectors

216
Q

types of plasma membrane receptors

A

ligand gated channels

GPCR

enzyme-linked receptors

217
Q

GPCR

A

signal activates enzymatic activity of a G protein

218
Q

GPCR pathway

A

ECM domain of a transmembrane receptor (often 7 spanning helices) binds molecule and transmits signal to cytoplasmic domain which changes conformation as a result and changes gene expression / has other effects

219
Q

GEF

A

guanine nucleotide exchange factor (transmembrane receptor acts as this)

allows GTP binding on Galpha

220
Q

G protein

A

guanosine nucleotide binding protein

tethered to membrane by covalently linked lipid
transmits signal to effector protein as a result of GTP-GDP exchange

221
Q

adenylyl cyclase

A

signal binds receptor on membrane

receptor binds G protein

G protein undergoes ADP-ATP exchange

makes cAMP with ATP

cAMP is second messenger and binds to PKA

PKA releases from catalytic subunit

catalytic subunit goes to nucleus and phosphorylates nuclear proteins to change gene expression

222
Q

kinases

A

enzymes that phosphorylate target proteins

223
Q

serine/threonine kinases

A

phosphorylate serine/threonine in target proteins (PKA, PKC)

224
Q

tyrosine kinases

A

phosphorylate tyrosine residues (RTKs, Src)

225
Q

what do phosphorylated proteins do?

A

can act as an adaptor or enzyme

226
Q

Receptor tyrosine kinases

A

single pass transmembrane proteins

dimerization and cross phosphorylation

227
Q

activated RTKs –> IP3 and PKA

A

–> activate phospholipase C –> IP3 / Ca2+ signaling and PKA activation

228
Q

activated RTKs –> proliferation

A

–> stimulates SH2 –> GEF (ras activating) –> + GTP, -GDP –> activated Ras –> MAP kinases –> proliferation

229
Q

activated RTKs –> cell growth + survival

A

–> PI3 kinase –> PK1 and PK2 –> cell growth + survival

230
Q

GEF

A

allows GTP binding

231
Q

GAP

A

GTPase stimulating

232
Q

GTPase

A

cleaves GTP –> turns off

233
Q

GDI

A

keeps GDP on; keeps protein off

234
Q

proteosome

A

degradation pathway; 50 protein subunits to degrade proteins by ATP hydrolysis

235
Q

functions of proteosome

A

removes misfolded or damaged proteins
maintains appropriate protein levels with controlled degradation
permits rapid responses to changing conditions

236
Q

ubiquitin

A

marks proteins for degradation (ubiquitination)

237
Q

E3 UB-ligases

A

degrade 1Kb allowing NFkB into nucleus

238
Q

Ikb

A

sequesters NFkB

MCB 2210 Cellular Biology (3 decks)

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