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Cellular And Molecular > Lecture 1: Membranes > Flashcards

Lecture 1: Membranes Flashcards

1
Q

What is Lecithin?

A

Amphiphilic
Phosphatidylcholibe is common in biological membrane
Named by polar head group
Variety of hydrophobic tails
Tails are Saturated or unsaturated fatty acids

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2
Q

What is sphingolipids?

A

Use sphingosine and fatty acid for hydrophobic side chains

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3
Q

What is cholesterol?

A 
Sterol
Required for membrane structure and flexibility 
Comprises about 30% of the membrane 
Essential for life 
We make it 
Associated with phospholipids 
Controls fluidity of membrane
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4
Q

What is integral membrane protein?

A

Integral monotopic protein
Singlepass protein
Multipass protein
Multi-subunit protein (ion channels form)

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5
Q

What is lipid-anchored membrane proteins?

A

Fatty acid
Isoprenyl anchor
GPI anchor

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6
Q

If membrane was lipid, what would they be?

A

Insulators

Not be able to pass molecules that are charged

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7
Q

What are lipid rafts?

A 
Membrane is not uniform 
Arranged in microdomains
Have more cholesterol
Membrane is thicker 
Generates a wider membrane than average 
Behaviour depends on lipid environment
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8
Q

What is phospholipid bilayer poorly permeable to?

A

Water and ions

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9
Q

Despite phospholipid bilayer being poorly permeable to water and ions, how can they pass these?

A

Water channels
Ion transporters
Hydrated ion selective Chanel

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10
Q

What happens at equilibrium?

A

Equal number of ions move back and forth to maintain the equilibrium

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11
Q

What perturbs ion distribution?

A

Presence of impermeant anion

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12
Q

Why is the presence of osmotically active and impermeant anions an issue?

A

Affect H20 balance

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13
Q

How do you neutralise the negative charges within the cell?

A

Actions flow in

Increases the osmotic pressure inside relative to the outside of cell

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14
Q

What does increased osmotic pressure force?

A

Water to flow into the cell

Tissue swelling

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15
Q

How do you even the osmotic forces?

A

Make Na+ ions effectively impermeant

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16
Q

What is transmembrane Na+ gradient used for?

A

Signalling

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17
Q

What is metabolic energy?

A

Sodium-potassium ATPase

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18
Q

What is the equilibrium state?

A

Equal movements of potassium down the concentration gradient and in reverse down the electrochemical gradient
When these are equal and opposite and there is no further charge movement

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19
Q

What do Na+ ions respond to?

A

Applied depolarisation

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20
Q

How is applied depolarisation transduced?

A

Channel

The channel has charged portion which can respond to changes in electrical field

21
Q

What goes down both concentration and chemical gradient?

A

Na+ ions

22
Q

What is action potential?

A

Where the influx of Na+ ions generate action potential upswing

23
Q

What is resting potential?

A

Where influx and efflux of charges are balanced

24
Q

What does the Nernst Equation calculate?

A

Exact values of the equilibrium potential in Mv

25
Q

What is the electrical potential?

A

The work per unit of charge required to move a charge from a reference point to a specified point

26
Q

What does the electrical potential represent?

A

Potential in Mv where there is no bet movement of charged molecules in or out of the cell for a given chemical potential

27
Q

Ek

A

Normally negative

28
Q

Ena

A

Normally positive

29
Q

What is the equilibrium potential for an ion?

A

The potential in which no current flows across the membrane

Potential gradient and concentration gradient of the ions cancel out

30
Q

What is the Nernst Equation?

A

Ex = RT/ZF x ln ([out]/[in])

31
Q

What is the reversal potential?

A

Membrane/Nernst potential of an ion which there is no net flow of a particular ion from one side of the membrane to the other

32
Q

20 degrees

A

58.2 log10 [out]/[in]

33
Q

37 degrees

A

61.5 log10 [out]/[in]

34
Q

Define capacitance

A

How quickly the membrane potential can respond to change in current

35
Q

Capacitance

A

How much charge is needed to cross the membrane to give a change in membrane voltage

36
Q

What happens to current injected into cell?

A

Most of the current will be used to change the membrane capacitance

37
Q

Large capacitance

A

More currents must flow to change the potential across it

38
Q

Smaller capacitance

A

Less current must flow to change to potential across it

39
Q

What is the capacitance taken to be?

A

1 mF/cm2

40
Q

Small neurons have a total capacitance of?

A

25-50 pf

41
Q

Nodes of Ranvier in large myelinated nerves are around?

A

1.5 or 2 pF

42
Q

What is the Goldman-Hodgkin-Katz voltage equation?

A

Tells you when a membrane is permeable to more than 1 ion simultaneously

43
Q

What does GHK equation incorporate?

A

Permeability terms for each of 3 Monovalent ions

44
Q

What contributes to setting the membrane potential?

A

Na+
K+
Cl-

45
Q

What is threshold?

A

Critical levels to which a membrane potential must be polarised to initiate action potential

46
Q

What are two types of threshold?

A

Voltage

Current

47
Q

What happens in voltage clamp?

A

The membrane potential is maintained constant or held at a command potential using a negative feedback

48
Q

What happens in current clamp?

A

The membrane potential can vary and the current applied is made to follow a command signal

49
Q

What is the property of cell membrane that holds charge?

A

Membrane capacity

Cellular And Molecular (9 decks)

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