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Intergrated physiology and pharmacology > Proteins and bioelectricity > Flashcards

Proteins and bioelectricity Flashcards

1
Q

What are the main ionic components of the intracellular fluid?

A
  1. High phosphate
  2. K+
  3. Low Na+
  4. Low Cl-
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2
Q

What are the main ionic components of the extracellular fluid?

A
  1. High Na+
  2. High Cl-
  3. Low phosphate
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3
Q

What are the 3 main types of membrane protein

A
  1. Carrier
  2. Channel
  3. Pump
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4
Q

List the order of speed of turnover of these proteins

A

Fastest- channel
carrier
Slowest- pump

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5
Q

What technique measures the activity of ion channels?

A

Patch-clamp technique

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6
Q

What are the 3 types of carrier?

A

Uniporter
Symporter
Antiporter

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7
Q

What is the structure of a bacterial K+ channel?

A

Tetramer
4 identical subunits
Arranged symmetrically around a central ion conducting pore

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8
Q

What are 4 characteristics of the Na+/K+ ATPase

A
  1. It is ubiquitous
  2. Pumps 3Na+ out for every 2K+ in
  3. Electrogenic (charge generating)
  4. tetramer structure- 2 alpha subunits, 2 beta subunits
  5. Maintains low intracellular Na+
  6. Critical for maintaining the resting membrane potential
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9
Q

What are the components of:

I=N.Po.g.(Vm-Ei)

A 
I- current
N- number of channels
Po- open probability of channels
g- single channel conductance 
Vm- membrane potential
Ei- equilibrium potential for the ion
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10
Q

How do you regulate the current?

A

Change the no. of channels- membrane shuttling
Change the open probability of a channel- phosphorylation, Ca2=, G proteins etc.
Change the Vm by activating or inhibiting other channels

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11
Q

How do you measure membrane potential?

A

Using glass micro-electrodes
Measures potential difference between inside and outside of cell
Vm=Vi-Vo
*Voltage sensitive fluorescent dyes

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12
Q

What are the concentrations of K+,Na+ and A- in the intracellular and extracellular fluid?

A

Na+- IC= 15mM, EC= 150mM
K+- IC=150mM, EC=5nM
A- IC=65mM, EC=0

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13
Q

What is the Nernst potential for an ion?

A

When all channels for a particular ion are open, and there is no net movement of the ion= Nernst potential for an ion

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14
Q

What is the Goldmann equation, and how is it different to the Nernst potenial?

A

Vm= RT/ZF x log pK[K+]o+pNa[Na+]o

/ pK[K+]i+pNa[Na+]i

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15
Q

What causes a change in Vm?

A

A change in the permeability of electrogenic transporters

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16
Q

How do you calculate the Nernst potential

A

Eion= RT/ZF x log [ion]out

/ [ion]in

17
Q

Why is it important that [Na+]i to be low?

A

1.Counter-current multiplication (in the thick ascending limb)- reabsorption of NaCl into blood
Activity of NKCC2 depends on inwards Na gradient
*If this is compromised- diuresis
2.Maintaining resting membrane potential in cells
*If [Na]i increases- problems with propagation of action potentials

18
Q

How is [Na+]i controlled?

A

Na/K ATPase

19
Q

What happens when ATP phosphorylates the pump?

A

Conformational change arises, faces outside- Na+ released outside the cell

20
Q

What limits the rate of this pump?

A

[K]o, [Na]i and ATP

21
Q

What is the concentration of calcium in the intracellular and extracellular fluid?

A 
Extracellular= 1million nM
Intracellular= 100nM
22
Q

What are the 2 classes of calcium store channels?

A
  1. IP3 receptor channels

2. Ryanodine receptors- low concentration of ryanodine activates the receptor

23
Q

What are the 4 types of calcium channel?

A
  1. Voltage gated Ca2+
  2. Receptor activated Ca2+ channels- NMDA etc
  3. Mechanically operated Ca2+ channels
  4. Store operated Ca2+ channels
24
Q

Why is Ca2+ regulation so important?

A

Ca2+ is important in second messenger signalling

25
Q

How is [Ca2+]i kept low?

A
  1. Na/Ca exchanger

2. Ca2+ ATPases

26
Q

How does the Na/Ca exchanger transport Ca against its concentration gradient?

A

Uses energy stored in the electrochemical gradient of Na+ by allowing 3Na+ to flown down its gradient in exchange for 1 Ca

27
Q

What are the 2 main types of Ca2+ ATPase

A

PMCA- Ca2+ out of the cell

SERCA- Ca2+ into sarcoplasmic reticulum

Intergrated physiology and pharmacology (19 decks)

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