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BMS 242 - Core Phys/pharm > Introduction > Flashcards

Introduction Flashcards

1
Q

What % of the membrane is:
Lipids
Proteins
Carbohydrates

A

Lipids - 42%
Proteins - 55%
Carbohydrates - 3%

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2
Q

Where are Na+ the highest?

A

In the plasma and interstitial fluid (extracellular)

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3
Q

Where are Na+ the lowest?

A

Intercellular fluid

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4
Q

Where are K+ the highest?

A

Intercellular

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5
Q

Where are K+ the lowest?

A

In the plasma and interstitial fluid (extracellular)

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6
Q

Where are Cl- the highest/lowest?

A

Highest outside of the cell

Lowest inside

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7
Q

Where are PO4^2- the highest/lowest?

A

Highest inside of the cell (ATP)

Lowest outside of the cell

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8
Q

Where is HCO3- found?

What is it important for?

A

In the interstitial fluid, plasma and intracellular fluid

Important pH buffer

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9
Q

Which cells have higher Cl- INSIDE?

A

Chloride secreting cells in the upper airway epithelial cells

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10
Q

What molecules are transported across the membrane via diffusion?

A

Lipid soluble molecules

O2, CO2

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11
Q

What molecules are transported across the membrane via transport proteins?

A

Small molecules and ions

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12
Q

What molecules are transported across the membrane via endocytosis?

A

Large molecules

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13
Q

What is another name for carrier proteins?

A

Facilitated transport proteins

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14
Q

What are carriers driven by?

A

The electrochemical gradient

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15
Q

What are examples of a carrier?

A

Sodium glucose cotransporter

Ion channels

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16
Q

What are primary active transport proteins?

A

Pumps
eg. ATPases
ONLY work if ATP is present

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17
Q

What is an important feature about channels?

A

They are GATED

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18
Q

Which transport proteins facilitate ACTIVE transport?

A

PUMPS

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19
Q

Which transport proteins facilitate PASSIVE transport?

A

Carriers and channels

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20
Q

What is active transport?

A

AGAINST the electrochemical gradient

Channels DIRECTLY hydrolyse ATP to change confirmation of the protein

Requires energy through ATP hydrolysis

Substances bind on one side of the membrane and are released on the other side, as a result of conformational change

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21
Q

What is passive transport?

A

FOLLOWS the electrochemical gradient

Are INDIRECTLY reliant on the NA/K ATPase to set up the electrochemical gradient

So they are INDIRECTLY reliant on ATP

Secondary active transport proteins

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22
Q

When is ATPase active transport needed?

A

When there is NO electrochemical driving force or when need to go AGAINST the electrochemical driving force

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23
Q

What is the transport rate of ATPase active transport?

A

LOW turn-over

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24
Q

What is the structure of Na/K ATPase?

A

Tetramer:
2 alpha subunits
2 beta subunits

25
Q

Where is Na/K ATPase found?

A

Ubiquitous (in nearly EVERY cell in the body)

NOT found in RBC of DOG

26
Q

What does Na/K ATPase transport?

What does this generate?

A

3 Na+ OUT
2 K+ IN

Generates a net loss of 1 positive charge from the cell - generating a -ve intracellular charge

27
Q

What does Na/K ATPase maintain?

What is this important for?

A

Low Na+ INSIDE the cell

Important to drive carriers and channels, which work with the electrochemical gradient

28
Q

What is the transport of carriers (facilitated transport proteins) dependant on?

A

The electrochemical gradient of at least ONE of the substances being transported (usually the Na+ gradient)

29
Q

What is the turnover of carriers?

A

High

30
Q

What can happen to carriers?

Why?

A

They can become SATURATED

As cannot put any more channels in the membrane

31
Q

What are the 3 classifications of carriers?

Describe them

A

1) UNIPORTER
- Transports 1 ion/solute
- DOWN the concentration gradient

2) SYMPORTER (co transporter)
- Transports 2 ions/solutes
- DOWN the concentration gradient

3) ANTIPORTER (exchanger)
- Transport one ion IN
- Transport on ion OUT

32
Q

What is an example of a uniporter?

A

Glucose transport protein

33
Q

What is an example of a cotransporter?

A

Sodium/glucose cotransporter

34
Q

What is an example of an exchanger?

A

Na/H exchanger

35
Q

What is the turn over of ion channels?

A

VERY high

36
Q

Why can the patch clamp technique be used?

A

When ions travel through an ion channel they generate a CURRENT as the ions are CHARGED

This current can be measured

37
Q

Are ion channels selective or non-selective?

A

BOTH

  • Can be selective for a certain ion (eg. Na+, Cl- etc.)
  • Can be non-selective for a certain group of ions (cation selective, anion selective)
38
Q

Who derived the patch clamp technique?

When?

A

Nehr and Sakmann

In 1993

39
Q

What can be identified using the patch clamp technique? (6)

A
  • What ion channels are present
  • What regulates these ion channels
  • Can identify SINGLE channels
  • Can identify the physiological function of the channels
  • Can identify pathophysioloigical CHANGES to a channel which cause disease
  • Can look at the impact on the cell when overexpress mutated channels
40
Q

Describe the process of the patch clamp technique

A
  • Glass electrode
  • Chloride metal wire attached to equipment
  • REFERENCE electrode sat in bath but also attached to equipment
  • Electrode looks at the DIFFERENCE between the 2 electrodes
    1) Bring glass electrode to touch cell membrane
    2) Seal cell membrane around the glass electrode
    3) Look at current flow
41
Q

As well as single ion channels, what can the patch clamp technique look at?

What is the method for this?

A

ALL the channels in the cell membrane

1) Pulses of suction to rupture the cell membrane
2) Solution in patch pipette - now intracellular solution
3) Can measure TOTAL current flow across the whole membrane
4) Clamp the potential and measure the current

42
Q

What equation which describes the total current?

A

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

I = total current 
N = number of channels in the membrane 
Po = open probability of the channels 
g = single channel conductance (a constant)
Vm = membrane potential 
Ei = Equilibrium potential
43
Q

What is the ‘open probability’ of a channel?

What scale is it measured on?

A

How often the channel is open

Measured on a scale 0-1:
0 = never open
1 = always open

44
Q

What 3 things can change the open probability of the channel?

A

1) Adding a phosphate
2) pH
3) G protein

45
Q

What is the equilibrium potential of an ion AKA?

A

Nerst potential

46
Q

What is Vm-Ei?

A

The POTENTIAL of the membrane (DRIVING FORCE of the ions)

47
Q

What is the relationship between driving force/potential and current?

A

The bigger the driving force, the bigger the potential

48
Q

What things can increase I (the total current)?

A

1) Increase no. of channels
2) Increase open probability (Gprotein, pH, phosphorylation)

3) Vm-Ei (driving force)
- Can increase membrane potential by opening/closing other channels which are electrogenic

49
Q

What is the structure of a Kv channel (voltage gated potassium channel)?

A

6 TM domains in each subunit

4 subunits together to make a functional channel

N and C are INTRACELLULAR

50
Q

What is the structure of a Kir channel (inwardly rectifying potassium channel)?

A

2 TM domains in each subunit

4 subunits to make functional channel

N and C are INTRACELLULAR

51
Q

What is the structure of a Nav channel?

A

24 TM in blocks of 6

N and C are INTRACELLULAR

52
Q

What is the structure of a Cav channel?

A

Same as Nav:

24 TM in blocks of 6
N and C are INTRACELLULAR

53
Q

What is the structure of a Ach channel?

A

4 TM

N and C are EXTRACELLULAR

54
Q

What is the structure of a CFTR Cl- channel?

A

12 TM

N and C are INTRACELLULAR

55
Q

What is the structure of a bacterial K+ channel?

A

Crystallised

Homologous to human Kir channel:

  • 2 Tm domains
  • 4 subunits to make functional channel
  • Pore in the middle where a TRAIN of K+ ions travel through
56
Q

Who discovered the structure of the bacterial K channel?

A

Rod MacKinnon in 1998

57
Q

What is the intracellular concentration of Cl-?

A

6 mM

58
Q

What is the extracellular concentration of Cl-?

A

100 mM

BMS 242 - Core Phys/pharm (13 decks)

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