Final Exam (cumulative) Flashcards
definition of a cell
smallest functional unit of an organism
cell appendages
microvilli: finger-like projections from cell surface, non-motile. increase surface area
primary cilium: non-motile, sensory function, ubiquitous
motile cilia: hair-like structures filled with microtubules, beat in unison and move mucus layer
flagella: long, whip-like structure found only in sperm, used for swimming
endosymbiotic theory
mitochondria and chloroplasts are descendants of previously free living prokaryotic cells. theory created by Lynn Margulis
plasma membrane structure
two leaflets oriented with tails together in middle. PS and PE inside leaflet, PC and sphingomyelin outside.
lipid rafts
areas of membrane with longer tailed FA and cholesterol and sphingolipids, allows for more transmembrane proteins and are membrane hotspots for transmission
how do alpha helices form in transmembrane proteins?
must by about 20-30 amino acids in length and consist primarily of amino acids having non-polar or hydrophobic side-chains
types of membrane proteins
Integral Transmembrane: single pass transmembrane multipass transmembrane beta-barrel transmembrane Integral Monotopic: hydrophobic alpha helix face inserts into one monolayer Anchored: lipid or GPI anchored into membrane Peripheral: associate with membranes non-covalently through integral proteins
topological equivalence
areas of the cell that have the same environment and are equivalent. includes the ER, Golgi, vesicles, and extracellular space
what determines permeability of a lipid bilayer?
molecular size electrical charge lipid-solubility hydrophobicity most soluble molecules are small, uncharged, hydrophobic, and lipid soluble
types of transport
passive: solutes move along gradient, no energy required
primary active: solutes move against gradient, direct energy requirement ((pumps))
secondary active: solutes move against gradient, uses favorable concentration gradient to move
symporter: coupled secondary active that moves both solutes in same direction
antiporter: coupled secondary active that moves solutes in opposite directions
how do pumps differ from coupled transporters?
pumps are enzymes, usually ATPases, that mediate primary active transport
coupled transport proteins are not enzymes, they are toggle proteins, that mediate secondary active transport
what is the resting membrane potential of a cell? how is it created?
RMP is the difference in electrical potential across the plasma membrane, magnitude is between -20 mV and -100 mV
created by K+ ions diffusing in both directions and having a higher concentration inside the cell
nodes of ranvier
VGNCs are only present at nodes of ranvier, so action potentials only occur at the nodes. results in saltatory (jumping) conduction which is much faster conduction
steps in vesicular chemical synaptic transmission
presynaptic depolarization by AP causes Ca2+ influx through VGCCs. exocytosis of neurotransmitter-containing synaptic vesicles and binding of neurotransmitter to postsynaptic receptors. this changes postsynaptic membrane conductance/potential, results in diffusion, degradation, and/or reuptake of neurotransmitter. synaptic vesicle membrane is retrieved and recycled
structure of nuclear envelope pores
big complexes that are selective (gated). channel nucleoporins act as size-selection filter, nuclear basket is located on nucleus side and cytosolic fibrils are on the cytosolic surface
steps in nuclear import
cargo with nuclear localization signal is recognized by nuclear import receptor and taken into nucleus. Ran-GTP binds and causes release of cargo and exits nucleus. Upon entering cytosol, Ran is hydrolyzed and Ran-GDP dissociates from receptor
steps in ribosomes docking to the ER
emerging protein has an ER signal sequence that an SRP binds to and halts translation. attached SRP binds SRP receptor in ER membrane and positions ribosome near protein translator channel complex which it docks with. once ribosome is docked, SRP and SRP receptor dissociate and translation continues feeding into ER
what does the seam in the translocator complex do?
allows for ejection of the protein at stop-transfer sequences via lateral gating. this creates transmembrane proteins
how are incompletely folded proteins prevented from leaving ER?
calnexin binds to unfolded proteins with terminal glucose residues and prevents them from leaving. glucosidase removes the glucose residues, but if protein fails to fold completely glucose residue is re-added by glucose transferase. cycle continues until folded correctly and no glucose residue is added, allowing protein to leave
how are phospholipids in membranes distributed appropriately? enzymes
ER scramblase: flips phospholipids from cytosolic to lumens leaflet
PM flippase: specifically flips PS and PE to cytosolic leaflet
PM scramblase: only active during cell death, events
types of coat proteins
clathrin: found in PM and trans-golgi
COPI: cis-golgi
COPII: ER
retromer: endosomes in retrieval pathway
steps in formation of vesicles (clathrin coated)
cargo receptors bind specific cargo and recruit to vesicle. adaptins bind cytosolic domains of cargo receptors and recruit clathrin. clathrin induces curvature and budding. the clathrin and adapting dissociate from vesicle after budding due to Rab hydrolyzing GTP.
