Unit 3 Flashcards
(138 cards)
1
Q
what is a tissue
A
group of cells working together
2
Q
how do tissues communicate
A
direct contact or intercellular junctions
3
Q
role of actin filaments
A
determine shape of cell’s surface, necessary for locomotion
4
Q
role of microtubules
A
determine positions of organelles and direct intracellular transport
5
Q
role of intermediate filaments
A
bear tension and maintain cell shape
6
Q
how can a plant transfer water and other soil nutrients from its roots, through stems, and to leaves
A
uses vascular tissues, plasmodesmata, channels that pass between adjacent plant cell walls connect their cytoplasm and enable transport of materials from cell to cell
7
Q
what are gap junctions
A
channels between adjacent cells that allow for transporting ions, nutrients, etc
8
Q
how do gap junctions develop
A
when set of 6 connexins arrange in elongated donut-like config (connexon)
9
Q
what is a tight junction
A
watertight seal between 2 adjacent animal cells, prevents materials from leaking
10
Q
what is the function of adherens junction
A
joins actin bundle in one cell to similar bundle in neighboring cell
11
Q
what type of junction is a desmosome
A
anchoring
12
Q
key components of desmosomes
A
cadherins, intermediate filaments
13
Q
what do desmosomes provide
A
tensile strength to epithelial tissues, preserve tissue integrity
14
Q
what are hemidesmosomes crucial for
A
anchoring epithelial sheet to underlying basal lamina
15
Q
which three junctions contribute to maintaining tissue integrity
A
hemidesmosomes, desmosomes, adherens junctions
16
Q
what do junctional complex proteins include
A
tight junctions, adherens junctions, desmosomal junctions
17
Q
purpose of anchoring junctions
A
transmit stress, provide structure, maintain tissue integrity
18
Q
what do tight junctions seal
A
gaps between cells and separate apical and basolateral surfaces
19
Q
what do adherens junctions link
A
epithelial cells to form adhesion belt
20
Q
what type of receptors in hemidesmosomes anchor cell to extracellular matrix
A
integrin
21
Q
gap junctions allow ___ molecules to pass from cell to cell
A
small
22
Q
role of extracellular matrix in tissues
A
ECM is network of proteins and carbohydrates; cells interact with ECM through integrin receptors for migration
23
Q
true or false: ECM is dynamic and continuously remodels
A
true
24
Q
what provides tensile strength in ECM
A
collagen
25
how are epithelial cells separated from underlying tissues
by basal lamina
26
what makes, excretes, and organizes components of the ECM
fibroblasts
27
what is the most abundant protein in ECM
collagen
28
what can incorrect collagen assembly cause
skin can be hyper flexible
29
what molecules in ECM bind to collagen fibrils outside cell
fibronectin
30
integrin receptors switch from ___ to ____ states
active to inactive
31
when does an integrin protein switch to an active conformation
when it binds to molecules on either side of the plasma membrane
32
true or false: integrin establishes a reversible mechanical linkage across plasma membrane
true
33
what is "outside-in activation"
binding of extracellular ligand causes unfolding of integrin, intracellular domains move apart and reveal binding site for intracellular adaptor proteins which leads to assembly of actin filaments
34
what is "inside-out activation"
when intracellular adaptor proteins bind to beta subunit, causes alpha and beta subunits to spring apart, driving extracellular portion of integrin into active conformation, process triggered by intracellular regulatory molecules
35
what do gels of polysaccharides and proteins that fill spaces in ECM do
resist compression, provide structural support
36
what is proteoglycans
hydrated gel-like substance where collagens and glycoproteins are embedded, resists compressive forces on matrix, permits rapid diffusion of nutrients, etc
37
what are fibrous proteins
collagen fibers strengthen and help organize matrix, elastin provides resiliency
38
what are matrix glycoproteins
help cells migrate, settle and differentiate in appropriate locations, components of basal lamina
39
describe the process of cell signaling (4 stages)
1. signal is sent from cell in response to enviro or molecular cue
2. signal is received by cell containing specific receptor for signal
3. signal is interpreted/transduced by receiving cell
4. cell responds in 1+ ways to signal
40
when does autocrine signaling happen
when cell releases ligand that is received by its own receptor, often occurs during early development of org to ensure that cells develop into correct tissues and take on proper function
41
what is signaling across gap junctions
transfer of signaling molecules directly next to target cell, allows group of cells to coordinate their response to signal that only one of them may have received
42
how are gap junctions different in plants
called plasmodesmata, form channels between adjacent cells (create giant communication network)
43
what is the most common type of cell signaling
paracrine
44
what is paracrine signaling
cell targets nearby cell
45
what must happen for paracrine signals to act only locally
ligand molecules are quickly degraded by enzymes or rapidly taken up by neighboring target cells
46
what is endocrine signaling
long range signaling mech by endocrine cells that secrete hormones as their signaling molecules
47
what does endocrine signaling rely on to have hormones travel through bloodstream
diffusion and blood flow
48
why do hormones act at a very low concentration
high specificity of receptor binding
49
which type of signaling is contact-dependent
juxtacrine
50
what is juxtacrine signaling
signaling that only influences cells that contact it, important during development and immune responses, direct cell-to-cell contact or interaction between cell-surface receptor and glycoprotein of ECM
51
how is neuronal signaling a specialized example of paracrine signaling
transfer of signal (neurotransmitter) between nerve cells at synapse
52
what are neurotransmitters
chemicals released at axon terminals that allow signals to be communicated to target cells
53
what does the synaptic gap allow for
rapid diffusion of neurotransmitter
54
what types of molecules function as signals
steroids, amines, peptides
55
how are hydrophobic signaling molecules transported through extracellular fluids to plasma membrane of target cells
by association with carrier proteins
56
what are type I intracellular receptors
anchored in cytoplasm by chaperone proteins, conformational change in receptor leads to release of chaperone protein that allows receptor to form homodimer w another receptor (glucocorticoid, androgen, progesterone receptors)
57
what are type II intracellular receptors
located in nucleus, receptors bound to co-repressor proteins which are released upon ligand binding, allowing receptor to bind to DNA and modulate gene expression
58
how are signals relayed in the cell
through signaling cascade
59
what are first messengers
extracellular signals whose binding by receptor proteins in plasma membrane initiates signaling cascade
60
what are second messengers
intracellular signaling molecules that spread signal to other parts of cell
61
what are effector proteins
intracellular targets that implement change in cell behavior (gene regulatory proteins, ion channels, etc)
62
define signal transduction
events that convert one type of signal to another type of signal
63
what does the speed of a response depend on
nature of target cell's response
64
what are protein kinases
enzymes that add 1+ phosphate to signaling protein, may activate or inactivate target protein
65
where is the energy required to drive phosphorylation cycle from
free energy of ATP hydrolysis
66
what do phosphate enzymes remove
phosphate group from target proteins and returns them to previous activity state
67
define amplification
when signal is relayed and activates a molecule, signal molecule can activate many other molecules
68
what is a scaffold protein
interacts w receptor and holds together other relay molecules in close proximity
69
what are desmosomes connected to in order to provide tensile strength
intermediated filaments
70
name 3 main types of cell surface receptors
ion-channel-coupled, enzyme coupled, and g-protein-coupled
71
describe ion-channel-coupled receptors
open/close ion channel upon activation; form channel in plasma membrane and binding of receptor causes conformational change in protein structure to allow ions to pass through
(sodium, calcium, magnesium, hydrogen)
72
what do enzyme coupled receptors activate when a ligand binds to the receptor
kinase
73
what does ligand binding promote in enzyme coupled receptors
dimerization and activation of intracellular domain
74
what is the results from ligands activated enzyme coupled receptors
downstream target proteins are phosphorylated to transduce signal
75
receptor tyrosine kinases are a common type of what kind of receptor
enzyme coupled receptor
76
what can cause a signaling protein to become activated
phosphorylation on tyrosine residues by RTK, conformational changes due to binding, close association with other proteins in signaling pathway
77
what is a common downstream effect of RTK
activation of Ras
78
what do the members of the Ras family of proteins do
they are all GTPases so they convert GTP to GDP
79
GDP is on or off
off
80
GTP is on or off
on
81
what must happen for Ras to be activated
second enzyme GEF (guanine-exchange factor) must be used to swap out GDP for GTP; activation of RTK receptor allows GEF to dock which ensures its in the right spot to activate Ras
82
what kind of binding is a common way to activate molecule switches
GTP binding:
small monomeric GTPases (Ras) help relay signals from cell surface receptors
large trimeric GTP binding proteins help relay signals from G protein coupled receptors and activate downstream effectors
83
how do GTPase activating proteins drive proteins into off state
increasing rate of hydrolysis of bound GTP
84
describe G-protein-coupled receptors
extracellular signal binds, receptor undergoes conformational change that enables it to activate trimeric G protein on other side of plasma membrane
85
true or false: the same extracellular signal can activate multiple different GPCR family members
true
86
which alpha helices of the GPCR binds to its trimeric G protein partner
5th and 6th
87
what are features of trimeric G-proteins
3 G-protein subunits in inactive state, G-alpha subunit that is active when bound to GTP, G-beta and G-gamma subunits remain associated when separated from G-alpha
88
what does the G-alpha subunit contain
GTPase domain (inactive when bound to GDP)
89
true or false: G-alpha can't separate from other two subunits when activated
false
90
describe the entire process of what happens when GPCR receptor binds to its ligand
undergoes conformational change and binds to G-protein, alpha/beta/gamma complex, causes GDP to be released from alpha subunit and get replaced by GTP, binding of GTP molecule causes beta/gamma complex to be released from alpha complex, separated G-protein subunits now considered active, G-alpha will slowly hydrolyze GTP so that its converted back to GDP which inactivates G-alpha subunit and causes all 3 G-proteins to become inactive
91
the longer the GPCR remains bound to its ligand, the ____ copies of its G protein it can activate
more
92
what do GPCRs commonly activate
adenylyl cyclase
93
what are the downstream effects of PKA activation by cAMP
activated GPCR activates G-alpha by swapping out GDP for GTP, alpha subunit then activates adenylyl cyclase enzyme to produce cAMP
94
what is necessary to activate protein kinase A
cAMP
95
what does GPCR-mediated activation of phospholipase C lead to
downstream activation of protein kinase c
96
what type of feedback does inhibition usually involve
negative
97
what do mitogens do
stimulate cell division
98
what conditions must be met for cell to pass G1 checkpoint
sufficient nutrients, sister chromatid separation complete, no detectable DNA damage, cell reached critical threshold size
99
what happens if conditions aren't met
cell enters resting state
100
what conditions must be met for G2 checkpoint
DNA replication must be complete and accurate, no DNA damage, cell must have reached certain minimum size
101
once G2 checkpoint is passed, can cell division stop
no
102
what conditions must be met for M checkpoint
mitotic spindles are assembled at opposite poles of cell, chromosomes are aligned at metaphase plate and properly attached
103
what do cdks do
phosphorylate intracellular proteins that initiate or regulate major events of cell cycle, constant throughout cell cycle
104
what do cyclins do
proteins that regulate activity of cdks, cyclically expressed over cell cycle
105
what does the cell control
activity of Cdks by synthesis and destruction of the cyclins
106
2 examples of cdk inhibitor proteins
p21 and p27
107
what does p53 do
inhibits entry into S phase when DNA damage is detected --> transcriptional regulator that stimulates transcription of genes encoding Cdk inhibitor proteins
108
what is a key function of G1/Cdk complexes
activate gene regulatory factors
109
start of mitosis is triggered by ___ and the end of mitosis is regulated by ____
M-Cdk; APC (anaphase promoting complex)
110
what phase do duplicated chromosomes condense
prophase
111
what are cohesins used for
hold sister chromatids together after replication
112
what do condensins do
pack DNA together tightly
113
what happens in prometaphase
nuclear envelope breaks down, chromosomes can now attach to spindle microtubules by kinetochores
114
what does the nuclear lamina do
provide structural support for nucleus and helps maintain chromosome organization, formed by intermediate filaments
115
difference between centromere, centrosome, and centriole
centromere: constricted region of chromosome
centriole: organelle composed of tubulin protein
centrosome: main microtubule organizing center
116
describe the 3 types of microtubule structures
kinetochore: attach to chromosomes
interpolar: microtubules from opposite poles
astral: anchor to plasma membrane
117
how does the cell monitor chromosome attachment
kinetochores of unattached chromosomes send stop signal to cell-cycle control system which inhibits further progress through mitosis by blocking activation of APC/C
118
what does the absence of APC/C prevent
destruction of cyclins so Cdks remain active (prolong mitosis)
119
name the errors in DNA replication
missense, nonsense, silent, frameshift
120
what are mutations random in respect to
location, nature, effect on fitness
121
what type of activity does DNA polymerase have
exonuclease
122
describe how DNA mismatch repair works
occurs AFTER replication has been completed, damage is cut out by a nuclease, original DNA sequence is restored by repair DNA polymerase, DNA ligase seals nick left in sugar
123
what is depurination
remove purine bases guanine or adenine from nucleotide but doesn't break DNA phosphodiester backbone
124
what is a major type of deamination
convert cytosine to uracil
125
what DNA excision repair corrects single base errors
base excision repair (important for repairing oxidative damage to DNA bases)
126
what can form a thymine dimer
uv radiation in sunlight
127
what DNA excision repair removes bulky adducts in double helix
nucleotide excision repair; DNA around lesion is locally unwound and incision of damaged DNA strand creates small DNA fragment with lesion which is removed, DNA polymerases fill in gap using complementary strand as template, DNA ligase seals
128
what are 2 mechanisms that can repair double stranded breaks caused by radiation/chemicals
nonhomologous end joining (quick but error prone) and homologous recombination (precise but requires template)
129
what happens in nonhomologous end joining
break is cleaned by nuclease to produce flush ends which are stitched together by DNA ligase
some nucleotides lost in repair process
130
what do mutations in somatic cells lead to
cancer within that tissue
131
what do mutations in germ cells lead to
inheritance of mutations
132
proto-oncogenes
code for positive cell cycle regulators that may be overactive in cancer
133
most cancers are what type of cancer
carcinomas (epithelial) bc of high turnover rate and exposure to environmental factors
134
impact of p53 mutation
cell cycle control programs that normally pause cell cycle for DNA repair are no longer functional, cell doesn't respond to signals that would normally lead to cell death
135
what does the emt do
provide epithelial cells with characteristics of increased motility and invasiveness
136
angiogenesis definition
new blood vessel formation
137
hallmarks of cancer
sustaining proliferative signaling, evading growth suppressors, activating invasion and metastasis, enabling replicative immortality, inducing angiogenesis, resisting cell death
138
