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Whitney - Biochem Test 2 > Lecture 19 Membrane Transport 2 > Flashcards

Lecture 19 Membrane Transport 2 Flashcards

1
Q

Types of Ion Channels

A

Voltage-gated Chemically Gated Mechanically Gated

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2
Q

Voltage Gated

A

Respond to change in membrane potential

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3
Q

Chemically Gated

A

Respond to ligands such as neurotransmitters

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4
Q

Mechanically Gated

A

Respond to mechanical stimuli, found in sensory neurons (detect vibration, pressure, stretch, touch, sounds, tastes, smell, etc.)

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5
Q

Patch Clamping

A

Proves existence of voltage gated channels

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6
Q

Putative Model of a Sodium Channel

A

260 kDa protein 4 internal repeats 6 transmembrane domains in each

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7
Q

In a sodium channel, which transmembrane protein is the voltage sensor?

A

TM 4

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8
Q

Putative Structure of Potassium Channel

A

6 transmembrane domains S1-S4 = voltage sensor S5-S6 = pore

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9
Q

Sodium and potassium channels are gated by membrane _____ or ______

A

potential or voltage

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10
Q

Sodium and potassium channels undergo _________ changes in response to changes in membrane potential.

A

Conformational

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11
Q

What is the ligand for acetylcholine receptor?

A

Acetylcholine

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12
Q

Where is the acetylcholine receptor located?

A

On the post-synaptic side

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13
Q

True or False: The acetylcholine receptor channel is more permeable to Na+ than K+.

A

False The channel is equally permeable to both Na+ and K+

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14
Q

Describe the Acetylcholine Receptor

A

Pentamer of 4 kinds of membrane spanning subunits arranged in the form of a ring that creates a pore through the membrane (2 alphas, beta, gamma, and delta)

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15
Q

Neurotransmission

A

Most important manifestation of membrane transport - the basis for communication in the nervous system

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16
Q

Nernst Equation

A

Veq = - (2.303) (RT/zF) log ([X]in/[X]out)

17
Q

Describe Each Number

A
  1. Resting membrane potential (-60mV)
  2. Depolarization stimulus
  3. Na+ channels open
  4. Rapid Na+ entry - further depolarization
  5. Na+ channels close, K+ open
  6. K+ move out
  7. Membrane hyperpolarization
  8. K+ channels close
  9. Cells return to resting potential
18
Q

Describe the steps of Synaptic Transmission

A
  1. AP reaches presynaptic terminal
  2. Depolarization opens up the VGCC
  3. Calcium enters cell
  4. Caused fusion of synaptic vesicles
  5. Exocytosis - release of NT in synaptic cleft
  6. NT bind to its receptor on post-synaptic side
  7. Opens up a lingand-gated channel
19
Q

Gap Junctions

A

Special form of ion channels

“Cell to Cell” channels

Important in cell to cell communication

20
Q

Structural Features of Gap Junctions

A

Packed in hexagonal array

Lumen ~20A

Distance between gap junctions of 2 adjacent cells is ~35A

21
Q

What can pass through gap junctions?

A

Small hydrophilic molecules and ions

Molecules less than 1 kDa (sugars, AAs, and nucleotides)

22
Q

What cannot pass through gap junctions?

A

Proteins, polysaccharides, and nucleic acids

23
Q

Structure of Gap Junctions

A

Each channel is made of 12 molecules of connexin

Six connexin molecules are hexagonally arrayed to form a half channel called connexon

Two connexons join end to end in intercellular space to form functional channel

24
Q

Why are gap junctions important in cardiac tissue?

A

Gap junctions ensure synchronous response to stimuli

25
Q

Why are gap junctions important in lens and bone tissue?

A

Distribute nourishment

26
Q

Gap Junctions are regulated by:

A

Membrane potential and hormone-induced phosphorylation

27
Q

Difference between ion channels and gap junctions

A

Gap juctions transverse 2 membranes, connect cytoplasm to cytoplasm, are synthesized by 2 different cells, and remain open for seconds to minutes

28
Q

Water channels/Aquaporins

A

Increase rate of water flow across membranes

29
Q

Where are water channels/aquaporins found?

A

RBC, Kidney, and Cornea

30
Q

Describe the structure of water channels/aquaporins

A

26 kDa protein

Have 6 transmembrane alpha helical domains

Whitney - Biochem Test 2 (6 decks)

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