Cell Membranes and Signaling Flashcards
membrane proteins allow…
- communication with outside environment
- specialized membrane functions
- some tethered to intracellular structures
Intergral membrane proteins
emebeded in membrane
Peripheral membrane protein
loosely attached
6 Membrane Protein functions
1) transport channels
2) receptors for signal transduction (nothing passes through membrane, more message is passed on causing other things to trigger)
3_cytoskeleton attachment
4) enzyme activity
5) intracellular attachment (cellular adhesion of molecules)
6) cell-cell recognition
amphipathic
partially hydrophobic, partially hydrophilic
what can just pass through membrane?
lipid soluble
fluid mosaic model
some of the membranes move sideways within the pane of the plasma membrane
fluid membrane
unsaturated (kinks)
viscous membrane
saturated (no kinks, packed tightly)
cholesterol…
reduces membrane fluidity at moderate temps but hinders solidification at low temps
an ice dwelling fish would…
have higher UNSATURATED fatty acids (harder to solidify)
diffusion:
substances move until they are equally and randomly distributed –> equilibrium
simple diffusion
:solutes move, ALWAYS move down concentration gradient
osmolarity
concentration metric, # of molecules per volume f fluid
osmosis
movement o water to equalize osmolarity (when salute cant pass, water will)
tonicity
ability of solution to alters cells water volume
plasmolyzed (plants)
shriveled (humans)
aquaporins
channel specifically for water
channel
mediated diffusion
- ion gated
-voltage gated
active transport
moves molecules against their concentration gradient, requires a carrier and energy input
carrier mediated diffusion
physically moves large molecules
co-transport
uses stored energy from active transport
1) active transport pumps ions uphill, creating a concentration gradient
2) the ions are allowed to flow down their concentration gradient
(builds concentration gradient in order to do other work)
vesicular (bulk) transport
endocytosis (bring inside)
exocytosis (taking cell outside)
electrogenic pump
contributes to voltage difference across plasma membrane
Local signaling
gap junctions
cell-cell recognition
paracrine(local regulator synaptic
long distance signaling
endocrine
nervous tissue
3 stages of cell signaling
1) reception: recognizing the signal molecule
2) transduction: convert original signal into form that can trigger cellular response
3) response: finally it triggers specific activity
ligand
signaling molecule that binds to another specific molecule
1) plasma membranes
2) intracellular receptors
G protein coupled receptor
- utilizes transmembrane receptors
- binds GTP (energy shuttle molecule similar to ATP) to a G protein
- activates another enzyme
ligand ion channel
- channel only opens with specific ligand binds
- allows movement of molecules that may trigger intracellular response
intracellular receptors
lipid soluble signal scan diffuse through plasma membrane!
ex. steroids
phosphorylation cascade
protein kinase: transfer a phosphate group –> phosphorylate –> active
protein phosphate: remove a phosphate group –> deactivate
