Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biochemistry > [2] Class 4: Transport Through Membrane 2 > Flashcards

[2] Class 4: Transport Through Membrane 2 Flashcards

1
Q

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

A

Ion channels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Why are transport ions 1000x faster than pumps?

A

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.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

3 types of ion channels:

A

Voltage
Ligand
Mechanical

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Respond to change in membrane potential

A

Voltage-gated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Respond to ligand such as neurotransmitters

A

Chemically gated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

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

A

Mechanically gated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How was ion channeling proven by experiment?

A

Patch clamping

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Who was involved in first patch clamping experiment?

A

Erwin neher and Bert Sakmann

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How long are ion channels open?

A

Msec ‘s

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Current applied to patch clamping

A

4 pA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

S5 and S6 form:

A

The pore of the ion channel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

S1-S4 form the:

A

Voltage sensor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Sequence homology:

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Model organism for Na+ channel testing:

A

Electric eel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

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

A

Na+ channel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the basis of topical anesthetics:

A

Block sodium channels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

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

A

Tetrodotoxin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Voltage sensor for K + channel

A

S1-s4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

S5-s6 K+ channel:

A

Pore

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Who determined structure of K+ channel and when?

A

Robert mackinnon; 1998

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

K+ direction of movement in tissue:

A

Move from inside out

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

HOw does selectivity filter work for K+ channel?

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is the signature of potassium channel?

A

TVGYG

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Which is larger? Na+ or K+

A

Na+ = 0.95 å

K is 1.33å

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

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

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

How many binding sites for K+ channel?

A

4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

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

A

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

28
Q

Na+/ K+ channels are gated by:

A

membrane potential or voltage

29
Q

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

A

Conformational change

30
Q

Voltage gated sponsors

A

S1-s4

31
Q

Pore of voltage gated channels:

A

S5-s6

32
Q

The duration of the open state can be controlled by length and flexibility of this part of the channel:

A

Ball and chain

33
Q

The ball and chain model inactivation domain is the:

A

Ball

34
Q

What creates a binding site for the + charged ball in the mouth of the pore?

A

Depolarization

35
Q

What happens when the ball binds to the mouth of the pore:

A

It is inactivated by occlusion.

36
Q

How many AA units make up ball:

A

20; Zaidia talked about 1st 40 AA important for closing the channel

37
Q

Ex of ligand gated ion channel

A

Acetylcholine receptor

38
Q

Present on post-synaptic side

Binds acetylcholine and open channel

Equally permeable to Na+ and K+

Pentamer of 4 kinds of membrane spanning (a2ßdelta) arranged in the form of a ring that creates a pore through the membrane

A

Ligand gated Acetylcholine receptor

39
Q

5 subunits come together to form a pore

A

Ach receptor

40
Q

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

A

Neurotransmission

41
Q

Nerve impulse is an ______ _______ produced by the flow of current across the plasma membrane of a neuron.

A

Electrical signal

42
Q

K+ and Na+ content inside of neuron

A

High [K+] and low [Na+]

43
Q

How is the K+/Na+ gradient generated?

A

Na+/K+ ATPase

44
Q

This is used to calculate membrane potential

A

Nernst equation

45
Q

Action potential rise from large transient

A

Changes in the permeability of axonal membrane to ions

46
Q

Conduction for _____ changes first d/t opening of ____channels

A

Na+; Na+

47
Q

__________ increases permeability to Na+ which begin to flow in via the Na+ chanel d/t high [ ] outside

A

Depolarization

48
Q

After Na+ rush in ________ then opens K+ channels and K+ move out

A

Depolarization

49
Q

Sequence of AP

A
  1. resting pot. -60mV
  2. Depolarizing 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
50
Q

Synaptic transmission steps:

A
  1. AP reaches presynaptic terminal
  2. Depolarization opens up the VGCC
  3. Ca++ enters cell
  4. Causes fusion of synaptic vesicles
  5. exocytosis- release of NT in synapse
  6. NT binds to receptor on post-synaptic side
  7. opens up ligand gated Na+ channel
51
Q

Special form of ion channel

Called “cell to cell’ channels

Passages btw contiguous cells

Important role in cell to cell communication

A

Gap junctions

52
Q

Packed in hexagonal array

Lumen ~20å

Distance btw gap junctions of 2 adjacent cells is ~35å

A

Structure of gap junctions

53
Q

Properties of gap junctions:

A

Small hydrophilic molecules and ions pass through

< 1 kDA molecules can pass: sugars, AA, and nucleotides can pass thru

Proteins, polysaccharides and nuclei acids cant pass

54
Q

Allow direct communication

A

Gap junctions

55
Q

Structure of gap junctions

A

12 molecules of transmembrane protein= connexin

6 connexin molecules hexagonally arrayed to form a half channel= connexon
2 connexons join end to end in the intercellular space to form functional channel.

56
Q

Physiological relevance gap junctions in cardiac tissue:

A

Synchronous response to stimuli - contraction in synchrony

57
Q

Significance of gap junctions in lens and bone

A

Distribute nourishment:

Sealed by high Ca+ and H+: protect norm cells from injured or dying cells b/c too much inside of too little outside can be fatal

58
Q

The induction of biological effects in cells that are not directly traversed by a charged particle

A

The bystander effect

59
Q

Differ Ion channels and GAP junctions membrane location:

A

Gap junctions: transverse 2 membranes

Ion: 1 membrane

60
Q

Differ Ion channels and GAP junctions connections:

A

GAP: connect cytoplasm to cytoplasm

Ion: Cytoplasm to ECM

61
Q

Differ Ion channels and GAP junctions synthesis:

A

GAP: synthesized by 2 different cells

Ion:

62
Q

Differ Ion channels and GAP junctions duration of acticity:

A

GAP: remain open for sec to min

Ion: open for only msec

63
Q

Water channels

A

Aquaporins

64
Q

Increase rate of water flow across membranes

Found in RBC, kidney, cornea

24 kDa protein

Have 6 transmembrane alpha helical domains

A

Aquaporins

65
Q

Structure of aquaporins

A

6 transmembrane alpha helical domains

Biochemistry (13 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions