Membrane Transport Flashcards

1
Q

What is permeable to the phospholipid bilayer?

A

Urea, ethanol, CO2, N2, O2, water

-low in cholesterol is more permeable to water. More cholesterol=less permeable to water

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2
Q

Electrochemical gradient

A

Combined effects of concentration and electric gradients on the direction of movement across a membrane

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3
Q

The 3 categories of membrane transport proteins

A

Channels, transporters, and ATP-powered pumps

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4
Q

Channels

A
  • multiple subunits arranged around central water filled pore
  • water, ions, small hydrophilic can move through
  • selective and very rapid movement down conc gradient.
  • most are gated
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5
Q

Transporters (carrier proteins)

A
  • bind substrate with high specificity
  • no direct connection between ECM and cytoskeleton
  • undergo change in conformation, much slower than channels but can move larger molecules
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6
Q

Cotransporters

A

Couple transport of a substrate against its gradient with one with the gradient. Secondary active transport since against the gradient is maintained by an active transport system.
-symporter(same direction) and antiporter(opposite directions)

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7
Q

ATP powered pumps

A
  • Use energy from the hydrolysis of ATP against gradients.
  • have ATPase domain that catalyzes ATP hydrolysis
  • primary active transport
  • undergo conformational changes during process
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8
Q

Aquaporins

A
  • integral membrane channel that selectively transports water.
  • waters main route, also transports small solutes but impermeable to charged particles
  • always open
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9
Q

Ion channels

A

-Ions flow thru ion channels passively down their electrochemical gradient
-selective
-different types.
Leak (always open)
Gated (open and close in response to stimulus)

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10
Q

3 properties of carrier mediated transporters

A

Specificity, competition, saturation

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11
Q

Na+/glucose cotransporter 1 (SGLT1)

A
  • small intestines and kidney
  • symporter of Na and glucose (from intestinal lumen to epithelial cells lining the small intestine)
  • 1 glucose (against gradient) per 2 Na (down its gradient)
  • Na provides energy for glucose to go against gradient (secondary active transport)
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12
Q

Chloride-bicarbonate exchanger (RBCs)

A
  • antiporter

- function is to increases CO2 carrying capacity of blood

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13
Q

Na/K pump (ATPase)

A

Maintains concentration gradients for each.

  • moves 3 Na out of cell, 2 K into cell for each ATP
  • P class pump
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14
Q

V class pumps

A

Energy from ATP hydrolysis to pump H+ against gradient from cytoskeleton to intracellular organelles

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15
Q

F class pumps

A
  • inner mitochondrial membrane
  • protons moving down gradient in F0 domain generates formation of ATP in F1 domain
  • aka ATP synthase
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