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37 Cards in this Set

  • Front
  • Back

Na+ & K+ Pump is an ATPase

how many ions does it pump in which direction?

What causes the conformational change?

When does ATP bind and release?

what type of port is it?

Pumps 3 Na+ out, 2 K+ in per ATP, against their concentration gradient

1. 3Na+ binds in un-P state

2. ATP binds, Autophosphorylation triggers conformational change

3. ADP dissociate, (still P) --> binding site opens --> Na+ leaves, 2 K+ enters

4. dephosphorylation --> K+ released inside cell

type: active antiport

K+ and Na+ gradient can be used as source of free E, give an example

Na+ down gradient,

glucose up gradient

both into the cell

Describe glucose is reabsorbed in epithelial cells.

name the 2 regions in epithelial cell

which part is active transport, which is passive, type of port?

what drives the active transport

Apical and basolateral plasma regions

Apical region:

ACTIVE symport driven by Na+ gradient

Basal region:

Passive uniport of glucose

Na+ & K+ pump

What is primary active and secondary active

Primary active : ATP driven

Secondary active: use of gradient

Ion channels:

4 types of gating

1. Voltage gated

2. ligand gated (extracellular)

3. ligand gated (intracellular)

4. mechanically gated

Ion channels:

passive or active transport?

what is a selectivity filter

give examples of K+ channel

Passive only - "Facilitated diffusion" (10^5 times faster than transporter)

Selectivity filter: ions transiently (ชั่วคราว) contact channel pore sidechain lining

K+ channel:

selectivity filter work in TETRAMER, hydrophillic sidechains make K+ ions think they are still in water with hydration shell

Na+ can't go through because too small, can't remain comfortably charge-shielded

Clicker: Why is ion channel so much faster than a transporter?

1. Diffusion is much faster, don't need conformational change

2. pore allows unhindered conformational change

3. more than one can occupy simultaneously

Resting potential

what id the difference between steady state and equilibium

potential of -70mV

there is a CONSTANT FLOW with NET FLOW = 0

Steady state: needs INPUT of E to maintain

Equilibrium: don't need E

Membrane is a capacitor,

how is this accomplished?

which part is + and - ?

the use of Na+&K+ ion pumps, ATPs are burning to keep this gradient

+++++ OUTSIDE +++++


- - - - - - INSIDE - - - - - - -

3 distinct states of voltage gated channels

1. Closed

2. Open

3. Inactivated - N-terminus of the channel protein blocks the flow rapidly

4 phases of the Action potential

1. Resting potential - steady state, balance in K+ pump and channel

2. Depolarization phase - as potential reaches the threshold level

Na+ flows into cell through ligand-gated channel

3. Repolarization phase - Voltage-gated K+ channel opens, K+ rush out of cell

4. Undershoot - "refractory period" channels are inactivated and wait until return to closed conformation

Why does action potential go in one direction only?

because need time in the refractory period

How does neurons propagate action potentials?

through waves of voltage-gated channel activation

Presynaptic ending --> as action potential reaches, V-Gated Ca2+ channels open, release neurotransmitter (signals) into the synapse

Postsynaptic dendrites --> ligand(neurotransmitter) gated Na+ channels activated, creates a new action potential

Intracellular compartments:


contains main genome, DNA and RNA synthesis

Intracellular compartments:


protein synthesis

glycolysis (glucose -->pyruvate)

AA & nucleotide synthesis

Intracellular compartments:

Endoplasmic reticulum (ER)

synthesis of

membrane proteins

secreted proteins


Intracellular compartments:

Golgi Apparatus

covalent modifications of proteins from ER,

sorting protein transport to other cellular parts

put lipids into membrane

Intracellular compartments:

Mitochondria and chloroplasts (Very general description)

ATP synthesis

Intracellular compartments:


degradation of intracellular organelles & material from outside

Intracellular compartments:


sort proteins received from:

endocytic pathway

golgi apparatus

Topology of the ER lumen

is topologically equivalent to outside of the cell
(pg 17) good summary diagram

Cis golgi

trans golgi

types of vesicle

cis - receive proteins

trans - release proteins in transport vesicles

secretory vesicles - to outside of cell

transport vesicles - within different organelles

How does golgi know where to send proteins to?

through the SIGNAL sequence in the protein, these direct the transport whether they should be sent to

import to ER

return to ER

outside the cell

import to nucleus

export from nucleus

Structure of the nuclear pore complex

what is perinuclear space

nuclear membrane is a DOUBLE bilayer,

perinuclear space = ER lumen

the pore allows both

simple DIFFUSION: small AA can still fuse when pore closes

ACTIVE TRANSPORT: Macromolecules

Nuclear localization Sequence (NSL)

what complex help them with transport

short AA sequence can appear anywhere,

are bound and carried through pore by Nuclear import receptors


How does the active transport mechanism through nuclear pores work?

What is used in cyclic enzyme activation and inactivation

phosphorylation using monomeric GTPases

Ran-GDP/GTP is attached to the NIR (nuclear import receptors)

OUTSIDE cell: high Ran GDP because Ran-GAP de-P the Ran GTP---> Ran GDP


INSIDE: high ran-GTP because Ran-GEF puts Ran-GTP onto the receptors


what are the important proteins used to help with unfolding/folding

which complexes are outside/inside the mitochondria

Chaperones are used to unfold protein to get through the pore, and re-fold when inside

TOM complex is outside, where it's receptor protein binds to the signal sequence of protein being imported.

TIM23 complex is inside, chaperone refolds protein, signal peptidase cleaves signal sequence --> mature protein ready to function

Comparison of nuclear and mitochondrial transport

signal sequence

Nuclear: anywhere, short and + charged

Mito: N-terminus amphipathic alpha helix

Comparison of nuclear and mitochondrial transport

Fate of signal sequence

Nuclear: unchanged after transport

Mito: removed by signal peptidase

Chloroplast: happen twice (have 2 signals) because have 2 inner membranes

Comparison of nuclear and mitochondrial transport


Nuclear: GTP hydrolysis

Mito: ATP hydrolysis, proton gradient

Comparison of nuclear and mitochondrial transport

conformation of protein

Nuclear: kept folded

Mito: unfolded through pore and refolded

Comparison of nuclear and mitochondrial transport

type of transport mechanism

Nuclear: Gated transport

Mito: transmembrane

Translocation of protein into the ER can happen in 2 ways

co-translational or post translational

what does a Signal Recognition Particle do?

target ribosomes to ER surfaces for translation of cotranslation translocation

The cellular functions of ER

- Entry point of secretory pathways

- establishes the protein orientation in the membrane (with lumen)

- site of lipid biosynthesis

- Initiation site of N-linked glycosylation (connecting proteins and functional groups)

-Intracellular storage of Ca2+

- detoxification: blood goes to liver and inside the ER has cytochrome P450 enzyme

Differences between rough and smooth ER

smooth (spaghetti)

rough (pancake) - has polyribosome bounded

signal recognition particle (SRP) --> translocation channel---> released into lumen OR stay in the membrane if it is a TMP

Sequences associated with the rough ER protein synthesis&translocation

Start transfer sequence - stick me into the pore, get cleaved and degraded after

Stop transfer sequence - let me stay in the membrane