Cell bio Chapter 15 Flashcards
Yeast respond to mating factors by forming
Schmoos
_________ is required if cells are to organize themselves and function properly as parts of multicellular organisms
communication
one type of signal converted to another
signal transduction
signaling requires cells to be in direct membrane-membrane contact
contact dependent
depends on signals that are released into the extracellular space and act locally on the neighboring cells
paracrine signaling
performed by neurons that transmit signals electrically along their axons and release neurotransmitters at synapses, which are located far away from the neuronal cell body
synaptic signaling
depends on endocrine cells, which secrete hormones into the blood stream for distribution all over body.
Endocrine signaling
work together to coordinate the activities of cells in widely separated parts of the body
endocrine cells and nerve cells
Different cell types respond _________ to the same extracellular signal molecules
differently
acetylcholine in salivary gland cells
causes secretion
acetylcholine in heart muscle cell
decrease rate and force of contraction
acetylcholine in skeletal muscle cell
cause contraction
response time if it requires changes in already present proteins in the cell
very rapid
response time if it involves gene expression and synthesis of new proteins
very slowly
programmed cell death
apoptosis
when deprived of all signals, cells activate a _________ program
suicide, called apoptosis
cells are programmed to respond to _________ extracellular signals
multiple
types of receptors signal molecules bind to
cell-surface receptors and intracellular receptors
signals that cannot pass the membrane and bind to cell surface receptors
hydrophilic signal molecules
signals that can pass through the membrane and bind to receptor proteins inside the cell
hydrophobic signal molecules
cell surface receptors relay extracellular signals via _______
intracellular signaling pathways
process of intracellular signaling pathways
- receptor binds to extracellular signal
- receptor activates intracellular signaling proteins
- ISP’s activate effector proteins
- effector proteins carry out specific cellular functions
intracellular signaling proteins act as _________
molecular switches
molecular switches in signal transduction are turned on or off by
addition or removal of phosphate groups
____________ adds a PO4 group and turns on the molecular switch using _______
protein kinase, ATP
___________ removes a PO4 group and turns off the molecular switch using _____
protein phosphatase, ATP
GTP-binding signals switch on and off by
adding a PO4 group to GDP to make GTP, or removing a PO4 group from GTP to make GDP
cell surface receptor fall into 3 main classes
ion-channel-coupled receptors, G-protein coupled receptors, enzyme-coupled receptors
ion-channel-coupled receptors facts
- typically multi pass transmembrane proteins
- signal opens and closes ion channel
- mediate rapid responses in nerve and muscle cells
G-protein coupled receptor facts
- receptor is typically a 7-pass transmembrane protein
- receptor acts through a trimeric GTP-binding protein (G-protein)
- G protein regulates activity of a separate plasma membrane-bound target enzyme or an ion channel
enzyme-coupled receptor facts
- single-pass transmembrane proteins
- function either directly as enzymes or are directly associated with enzymes (e.g. kinases and phosphatases) that they activate
largest class of cell-surface receptors (more than 700 in humans)
G-protein-coupled-receptors (GPCRs)
almost half of all known drugs act through ______
GPCRs or G-protein-coupled-receptors
hundreds of ________ are concerned with the sense of smell
GPCRs
GPCR structure
- single polypeptide chain passing in the cell membrane ______ times
- receptor site faces _______
- G protein interaction site is on ________
- 7 times
- extracellular space
- cytoplasmic side
GPCR receptors act through a _______
trimeric GTP-binding protein (G-protein)
trimeric G protein facts
- A trimeric protein made of _____
- in the inactive form _____ is bound to GDP, in the active form this is replaced with GTP
- ______ is bound to alpha and gamma subunits she in the inactive state
- the alpha and gamma subunits are ______
- alpha, beta, and gamma subunits
- alpha subunit
- beta subunit
- attached to the plasma membrane through anchors (covalently attached lipid molecules)
when activated, the alpha subunit of g-proteins carry
intrinsic GTPase activity, passing a phosphate group to other proteins to activate them.
the activated alpha subunit of the G-protein can also activate membrane bound
enzymes
cAMP levels are controlled by
- adenylyl cyclase makes cAMP from ATP
2. phosphodiesterase breaks down cAMP
Cholera bacterium create cholera toxin, a protein that enters cells in the intestine and modifies the ______ to stimulate ________. The altered _________ is continuously active and keeps signaling to its target proteins.
alpha subunit of G-protein
adnylyl cyclase
alpha subunit
cyclic-AMP regulates __________ which has an effect on _______ and __________
adrenaline
skeletal muscle
glycogen breakdown
cAMP mediates adrenaline by activating
protein kinase A (PKA)
cAMP activation of protein kinase A (PKA) can activate _________
gene transcription
some G proteins regulate the activity of
phospholipase C
GPCRs increase cytosolic Ca2 and activate _____
PKC
GPCR signaling through phospholipase C
Signal 1: ____ is water soluble and diffuses through the cytosol where it binds to ____ receptors on the ER. Ca2 is released into the cytoplasm.
Signal 2: _____ remains imbedded in the membrane. _______ activates protein kinase C (PKC) along with Ca2. PKC then acts on a number of different substrates.
Signal 1: IP3
Signal 2: diacylglycerol
Among the enzyme-coupled cell-surface receptors, ___________ are particularly abundant in mammalian cells.
receptor tyrosine kinases (RTKs)
_______ are key regulators of normal cellular processes and also have a critical role in the development and progression of many types of cancer.
Receptor tyrosine kinases (RTKs)
enzyme coupled receptors facts
- single-pass transmembrane protein
2. cytosolic domain functions as an enzyme or is directly associated with enzymes
Binding of signal molecules cause RTKs to ______. The RTKs _______ themselves and their interacting partner.
dimerize
phosphorylate
Phosphorylated RTKs serve as __________ for other signaling proteins
docking sites
Most RTKs activate the monomeric ________
GTPase Ras
GTPase Ras facts
- Ras is a small GTP binding protein that relays signal from RTKs
- Ras contains covalently attached lipid molecules that anchor the protein to the cell membrane
- Ras resembles the alpha subunit of GPCR and functions as a molecular switch in the same way
30% of human tumors have activated forms of ____
Ras
