Chapter 9 - cell communication Flashcards
1
Q
cell communication
A
- the process of cells detecting and responding to signals in the extracellular environment
2
Q
how do receptors translate the signal from outside to inside the cell?
A
- when the signal attaches, the receptor changes conformation
3
Q
ligand
A
- signaling molecule binds to a protein, such as an enzyme, a receptor, or a channel
- signaling molecule
4
Q
what happens to a receptor when a ligand binds to it?
A
- it changes conformation
5
Q
Cell surface receptors
A
- receptors found in the plasma membrane that enables a cell to respond to different kinds of extracellular signaling molecules
6
Q
enzyme- linked receptors
A
- found in all living species
- extracellular domain binds to signal
- intracellular domain becomes functional catalyst
- most are protein kinases
7
Q
why is cell signaling important?
A
- allows the cell to respond to a changing environment
8
Q
explain yeast cell response to glucose
A
- glucose attaches to glucose receptors
- receptors cause response inside cell to produce glucose transporters and enzymes to metabolize glucose
- without the presence of glucose, these genes stop being expressed
9
Q
phototrophism
A
- cellular response to allow the plant to bend towards the sun
- triggered by auxin
10
Q
auxin
A
- signaling molecule for phototropism
- inhibited by light
- transmitted from cell to cell
11
Q
direct intercellular signaling
A
- cell junctions allow signaling molecules to pass from one cell to another
- pass directly from the cytosol of one cell to the next
12
Q
contact-dependent signaling
A
- molecules bound to the surface of cells serve as signals to cells coming in contact with them
13
Q
autocrine signaling
A
- cells secrete signaling molecules that bind to their own cell surface or similar neighboring cells
14
Q
paracrine signaling
A
- signal does not affect originating cell but does influence nearby cells
15
Q
endocrine signaling
A
- signals called hormones travel long distances and are usually longer lasting in effect
16
Q
three stages of cell signaling
A
- receptor activation
- signaling molecule binds to receptor - signal transduction
- activated receptor stimulates a sequence of changes
- done via signal transduction pathway - cellular response
- different responses possible- change enzyme activity
- change function of structural proteins
- change gene expression
17
Q
describe the binding between a receptor and a ligand
A
- highly specific
- non covalent
- rapid bond and release
- causes conformational change, which causes the ligand to detach
18
Q
three types of cell surface receptors
A
- enzyme-linked receptors
- G-protein coupled receptors (GPCR)
- ligand gated ion channels
19
Q
Enzyme linked receptors
A
- found in all living species
- extracellular domain binds to signal
- intracellular domain becomes functional catalyst
- most are protein kinases (phosphorylates things)
20
Q
G-protein coupled receptors (GPCR)
A
- found in all eukaryotic cells
- has 7 transmembrane segments
- when activated by a signaling molecule, binds to G proteins to replace GDP with GTP
- alpha and beta/y subunits separate and can promote cellular responses
21
Q
kinase
A
- enzyme that phosphorylates things
- takes a phosphate and attaches it to something else
22
Q
Ligand-gated ion channels
A
- found in plant and animal cells
- ligand binding causes the channel to open and ions flow through
- used in synaptic signals between neurons and muscles or between two neurons
- allows the body to create current/action potentials
23
Q
intracellular receptors
A
- some receptors such as estrogen are inside the cell
- hormone passes through the membrane and into the nucleus where it binds to the estrogen receptor
24
Q
what is phosphotase
A
removes phosphates
25
Q
Signal transduction pathways (what causes them and what they do)
A
- signaling molecule binds to the cell surface receptor, causing conformation change on the inside of the cell
- some lead to kinase cascade
- some cause generation of second messengers (relay signal to proteins)
26
Q
Receptor tyrosine kinase (RTK)
A
- category of enzyme-linked receptors found in animals
- can target certain amino acid called tyrosine to phosphorylate it
- ex: growth factor
27
Q
Epidermal growth factor (EGF) pathway
A
- growth factor stimulates cell growth or division
- mostly stimulates epidermal cells to divide but has other functions
- binding of EGF signal to receptor triggers protein kinase cascade all to way to nucleus, where cellular response occurs
28
Q
what does RAS do?
A
- GDP is replaced with GTP to activate RAS
- actives a protein kinase cascade
- has auto GTPase activity to prevent cell from uncontrollable dividing
- mutations in raw are associated with most cancers because it inhibits the GTPase activity
29
Q
cAMP
A
- epinephrine binds to signaling molecule
- alpa subunit of G protein binds to adenylyl cyclase, which stimulates cAMP from ATP
- cAMP binds to regulatory subunits of PKA, releasing the catalytic subunit
- catalytic subunits of PKA can phosphorylate other proteins, which causes cellular response
30
Q
second messengers
A
- small molecules or ions that relay signals inside the cells
- produced quickly and duration is short
- ex: cAMP
31
Q
synthesis and breakdown of cAMP
A
- synthesis is triggered by an alpha subunit of a G protein binding to adenylyl cyclase
- adenylyl cyclase makes cAMP out of ATP
- cAMP is inactivated by phosphodiesterase
- converts cAMP back to AMP
32
Q
adenylyl cyclase
A
- synthetic enzyme responsible for the synthesis of cAMP
33
Q
phosphodiesterase
A
- breaks down cAMP
34
Q
advantages of cAMP
A
- signal can be easily amplified
- activates lots of PKA, which leads to more phosphorylation of proteins
- fast
- substantial amount of cAMP can be made within 20 so the signal
35
Q
How does hormone signaling work in multicellular organisms
A
- hormones are spread to lots of cells via endocrine signaling
- response to the signal depends on which cell is responding
- variation in response is determined by the proteome
- ex: epinepherine
36
Q
differential gene expression
A
- all cells contain the same genome but only express particular genes
effects cellular response by:
1. receptor may not be expressed
2. different receptors for the same signal
3. different affinities for signal
4. signal transduction pathways different
37
Q
apoptosis (general)
A
- programmed cell death
- nucleus and cytoskeleton destroyed, causing cell to shrink
- plasma membrane forms blebs that break away
- macrophages take blebs away
38
Q
caspase
A
- drives apoptotic cascade
- inactive version is procaspases
- cleaves cellular protein, causing cell to shrink and form blebs
39
Q
Apoptosis through signal transduction
A
