Brainscape's Knowledge GenomeTM

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


See full index

BC3003: Introduction to Cell Biology & Biomembranes > Transport of Molecules Aross Membranes: Transporters & Ion Channels > Flashcards

Transport of Molecules Aross Membranes: Transporters & Ion Channels Flashcards

1
Q

How do Transporters / Carriers transport molecules?

A

Through cycles of conformational changes

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

Do Transporters / Carriers have a high or low rate of transport?

A

Low

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

Do Uniporters transport molecules UP or DOWN their concentration gradients?

A

Down

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

How do Symporters and Antiporters transport molecules?

A

Couple the transport of one type of molecule UP its concentration gradient to the transport of another molecule(s) DOWN an electrochemical gradient

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

What is an example of a Uniporter?

A

GLUT1
* glucose transporter

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

What is an example of a Symporter?

A

Two-Na+ / One-Glucose Symporter
* transports Na+ DOWN its concentration gradient
* transports Glucose UP its concentration gradient

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

Why are TWO Na+ ions used in the Two-Na+ / One-Glucose Symporter?

A
  • Transport of 2 Na+ provides twice as much energy
  • Allows symporter to transport Glucose against a much steeper concentration gradient
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is an example of a Uniporter and Symporter working together?

A

2-Na+ / 1-Glucose Symporter + GLUT2 glucose uniporter
* work together to take up glucose from the gut
* 2-Na+ / 1-Glucose symporter in the microvilli transports glucose UP its concentration gradient from intestine into cells
* Glucose uniporter transports glucose into blood by facillitated diffusion

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

What are THREE Antiporters involved in regulating cellular pH?

A
  1. Na+ / H+ antiporter
  2. Na+ HCO3- / Cl- antiporter
  3. Cl- / HCO3- antiporter
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How does the Na+ / H+ antiporter regulate cellular pH?

A

Exports H+ which Raises pH

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

How does the Na+ HCO3- / Cl- antiporter regulate cellular pH?

A

Imports HCO3- which Raises pH

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

How does the Cl- / HCO3- antiporter regulate cellular pH?

A

Exports HCO3- which Lowers pH

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

How is the opening/closing of Resting (Non-Gated) Ion Channels regulated?

A

Not regulated by any external factors

  • open probability is an intrinsic property of the channel
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How is the opening/closing of Voltage Gated Ion Channels regulated?

A

Regulated by the electrical potential across the membrane
* open probability depends on Vm (voltage across membrane)

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

How is the opening/closing of Ligand Gated Ion Channels regulated?

A

Regulated by binding of one or more ligands to channel
* open probability depends on ligand

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

What is an example of a Resting (Non-Gated) Ion Channel?

A

Resting K+ channel from Streptomyces lividans

17
Q

How is the Resting K+ Ion Channel selective for the larger K+ ion over the smaller Na+ ion?

A
  • K+ is normally coordinated to 8 water molecules
  • Must lose water to pass through channel
  • 8 backbone Carbonyl oxygens from conserved Glycine residues coordinate K+ in the pore
  • Several K+ ions move “in step” through the selectivity filter
  • Na+ is too small to be coordinated properly by the Carbonyl oxygens and so can’t shed its water and can’t enter pore
18
Q

What is an example of a Voltage-Gated Ion Channel?

A

Voltage-Gated Channels in neurons

19
Q

What is Mytonia and what causes it?

A
  • Delayed relaxation of muscle after contraction
  • Characterised by decreased Cl- conductance of muscle cells
20
Q

What mutation causes congenital myotonia in fainting goats?

A

Ala 855 Pro mutation in voltage gated Cl- channel gClC-1
* decreased opening probability at physiological Vm

21
Q

What does a mutation in the sodium channel SCN1A cause?

A

Epilepsy

22
Q

What is an example of a Ligand-Gated Ion Channel?

A

Nicotinic Acetylcholine Receptor (nAChR) at the NMJ

23
Q

How many subunits does an nAChR have?

A

5 (pentameric)

24
Q

How many binding sites does an nAChR have?

A

Two acetylcholine binding sites

25
Q

Are nAChR channels fast or slow acting?

A

Fast.
* channel opens within milliseconds of ACh binding

26
Q

What forms the gate on an nAChR channel?

A

Kinked M2 helices to constrict the pore / gate
* conformational change on ligand binding causes helices to rotate, opening the gate

27
Q

How wide is the gate on an nAChR channel when open?

A

0.6 - 0.8 nm
* allows cations to pass through WITH water

BC3003: Introduction to Cell Biology & Biomembranes (15 decks)

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