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level: transport through cell membrane

Questions and Answers List

level questions: transport through cell membrane

QuestionAnswer
K+___ gradient is a major determinant of electrical excitability
1. simple diffusion 2. faciliated diffusion 3. osmosis3 types of passive transport
random movement of particleswhat is Brownian Motion?
higher; lower -but not necessarily on purposeparticles move from area of ____ concentration to areas of ____ concentration.
1. size 2. lipid-solubility 3. chargemembrane permeability based on (3):
-no energy needed -no carrier proteins needed -lipid-soluble molecules easily cross -other small lipid-insoluble can use channelscharacteristics of simple diffusion
1. gated= some stimulus must open in 2. non-gated= tunneltwo types of channels
1. voltage-gated channels 2. ligand-gated channelstwo types of gated channels
Human Aquaporin Iex of non-gated tunnel
1. size 2. shape 3. chargechannels are selectively permeable based on (3):
1. at resting conditions, gates are closed 2. stimulation -either alternation in membrane voltage or binding of ligand 3. channel openssummary of control of diffusion
TRUET/F: potential has to reach a threshold to open the gate.
FALSE -all or noneT/F: channel gates can halfway open.
1. membrane permeability 2. concentration difference across the membrane 3. effect of electrical potentialfactors influencing diffusion (3):
fick's lawwhat concept related to concentration differences?
nernst equationwhat concept relates to electrical potential?
1. thickness of membrane 2. lipid solubility of substance itself 3. # of protein channel available 4. size of diffusing substancemembrane permeability in diffusion depends on (4):
rate of diffusion across cell membrane is proportional to concentration difference & permeability of partition to solutionconcentration difference in diffusion
rate= permeability coefficient x (Ci-Co) -holds true for uncharged moleculeFick's Law
-movement is not random when electrical force influences motion -have to take into account concentration difference and electrical pull -equilibrium develops b/w concentration gradient & electrical gradient rep'd by Nernst Equationeffect of electrical gradient in diffusion
equilibrium that develops b/w concentration gradient and electrical gradient - EMF= (+/-)61logCi/CoNernst Equation
-occurs in direction of electrochemical gradient -no energy required -movement of solutes via carrier proteins -can become saturatedcharacteristics of facilitated diffusion
FALSET/F: carrier proteins and channel proteins are the same.
-double-gated binding sites -finite # of binding sites (limit on transport rates) -3 types (uni-, sym-, antiporter)characteristics of carrier proteins
1. uniporter= one molecule 2. symporter= 2 diff molecules in same direction 3. antiporter= 2 diff molecules in diff directions 2&3 most common3 classifications of carrier proteins
-water moving from area of high water to low water OR low solute to high solute -net movement can cause cell to shink or swell -can create pressure diff if solute concentration REALLY differscharacteristics of osmosis
water will only push until pressure of gravity on solute side balances pressure of water movement - hydrostatic pressure = osmotic pressureconcept of osmotic pressure
1. movement of molc/ions "uphill" against concentration gradient 2. can establish/maintain concentration gradient 3. requires energy 4. has specificity, saturation, & competition bc of carrier proteinscharacteristics of active transport (4)
1. primary 2. secondarytypes of active transport
1. uses ATP to move molecule "uphill" against concentration gradient 2. ATP-powered pumps used for thischaracteristics of primary AT
1. ATP binding sites on cytosolic/cell sides 2. ATP -> ADP + Pi when molecules/ions transportedcharacteristics of ATP powered pumps
1. p-pumps 2. f-pumps 3. v-pumps 4. abc-pumpsfour classes of ATP powered pumps
Na+/K+ pump - 2 K+ in/ 2 Na+ out/ 1 ATP used -maintains resting membrane potential -present in all cells of the bodyexample of MOST important p-pump & characteristics
H+-K+ pump -in stomach, kidney, intestines -2 H+ in/ 2 K+ out/ 1 ATP usedexample of a lesser important p-pump
Ca2+ pump aka PMCA - found in possibly all cells & ER & SR - CA2+ out of cellsanother example of lesser important p-pump
-does not use ATP directly -uses energy of downhill movement of other moleculecharacteristics of secondary active transport
1. cotransporters (symporters) 2. exchangers (antiporter/countertransport)two major types of secondary active transport
Na+ Glucose transporter -energy to move glucose against concentration gradient comes from NA+ electrochemical gradient - glucose piggybacking on Na+ passively going inexample of secondary active transport