[2] Class 4: Transport Through Membrane 2 Flashcards Preview

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Flashcards in [2] Class 4: Transport Through Membrane 2 Deck (65)
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1

Integral, polytopic membrane proteins

400 genes in human genome

Mediates Facilitated passive transport

Highly selective and specific for ions

1000X faster than pumps

Opening and closing channels shapes membrane potential

Ion channels

2

Why are transport ions 1000x faster than pumps?

They have efficient gates that can be voltage gated and not require the sequential steps of waiting for ATP binding and hydrolysis for the action to occur.

3

3 types of ion channels:

Voltage
Ligand
Mechanical

4

Respond to change in membrane potential

Voltage-gated

5

Respond to ligand such as neurotransmitters

Chemically gated

6

Respond to mechanical stimuli, detect vibration, pressure. Stretch, touch, sounds, tastes, smell, heat, volume, and vision. Found in sensory neurons:

Mechanically gated

7

How was ion channeling proven by experiment?

Patch clamping

8

Who was involved in first patch clamping experiment?

Erwin neher and Bert Sakmann

9

How long are ion channels open?

Msec 's

10

Current applied to patch clamping

4 pA

11

S5 and S6 form:

The pore of the ion channel

12

S1-S4 form the:

Voltage sensor

13

Sequence homology:

Sodium, Ca+, K+ all homologous seem to be handed down in evo.

14

Model organism for Na+ channel testing:

Electric eel

15

260 kDa protein
4 terminal repeats
6 transmembrane domains
TM 4-voltage sensor

Na+ channel

16

What is the basis of topical anesthetics:

Block sodium channels

17

Toxic substance from pufferfish that acts to inhibit Na+ channels:

Tetrodotoxin

18

Voltage sensor for K + channel

S1-s4

19

S5-s6 K+ channel:

Pore

20

Who determined structure of K+ channel and when?

Robert mackinnon; 1998

21

K+ direction of movement in tissue:

Move from inside out

22

HOw does selectivity filter work for K+ channel?

Hydrated K+ dehydrated when going through selectivity filter. Carbonyl bonds are forms w/ AA's in channel. Rehydrated exiting channel.

23

What is the signature of potassium channel?

TVGYG

24

Which is larger? Na+ or K+

Na+ = 0.95 å

K is 1.33å

25

Why cant Na+ pass through K+ channel if it is smaller than K+?

Na+ is rejected b/c of higher energetic cost of dehydrating sodium would not be recovered when passing through channel.

K+ resolvation energy > desolvation energy

26

How many binding sites for K+ channel?

4

27

Describe the fundamental reason that K+ ions continue through channel as opposed to remaining bonded to carbonyl of AA in pore:

D/t repulsion of like charges- K+ ions push each other along as more come into pore

28

Na+/ K+ channels are gated by:

membrane potential or voltage

29

What happens in voltage gated channels in response to changes in membrane potential?

Conformational change

30

Voltage gated sponsors

S1-s4