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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
Where is Na/K ATPase found?
Ubiquitous (in nearly EVERY cell in the body) NOT found in RBC of DOG
26
What does Na/K ATPase transport? What does this generate?
3 Na+ OUT 2 K+ IN Generates a net loss of 1 positive charge from the cell - generating a -ve intracellular charge
27
What does Na/K ATPase maintain? What is this important for?
Low Na+ INSIDE the cell Important to drive carriers and channels, which work with the electrochemical gradient
28
What is the transport of carriers (facilitated transport proteins) dependant on?
The electrochemical gradient of at least ONE of the substances being transported (usually the Na+ gradient)
29
What is the turnover of carriers?
High
30
What can happen to carriers? Why?
They can become SATURATED As cannot put any more channels in the membrane
31
What are the 3 classifications of carriers? Describe them
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
What is an example of a uniporter?
Glucose transport protein
33
What is an example of a cotransporter?
Sodium/glucose cotransporter
34
What is an example of an exchanger?
Na/H exchanger
35
What is the turn over of ion channels?
VERY high
36
Why can the patch clamp technique be used?
When ions travel through an ion channel they generate a CURRENT as the ions are CHARGED This current can be measured
37
Are ion channels selective or non-selective?
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
Who derived the patch clamp technique? When?
Nehr and Sakmann In 1993
39
What can be identified using the patch clamp technique? (6)
- 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
Describe the process of the patch clamp technique
- 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
As well as single ion channels, what can the patch clamp technique look at? What is the method for this?
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
What equation which describes the total current?
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
What is the 'open probability' of a channel? What scale is it measured on?
How often the channel is open Measured on a scale 0-1: 0 = never open 1 = always open
44
What 3 things can change the open probability of the channel?
1) Adding a phosphate 2) pH 3) G protein
45
What is the equilibrium potential of an ion AKA?
Nerst potential
46
What is Vm-Ei?
The POTENTIAL of the membrane (DRIVING FORCE of the ions)
47
What is the relationship between driving force/potential and current?
The bigger the driving force, the bigger the potential
48
What things can increase I (the total current)?
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
What is the structure of a Kv channel (voltage gated potassium channel)?
6 TM domains in each subunit 4 subunits together to make a functional channel N and C are INTRACELLULAR
50
What is the structure of a Kir channel (inwardly rectifying potassium channel)?
2 TM domains in each subunit 4 subunits to make functional channel N and C are INTRACELLULAR
51
What is the structure of a Nav channel?
24 TM in blocks of 6 N and C are INTRACELLULAR
52
What is the structure of a Cav channel?
Same as Nav: 24 TM in blocks of 6 N and C are INTRACELLULAR
53
What is the structure of a Ach channel?
4 TM N and C are EXTRACELLULAR
54
What is the structure of a CFTR Cl- channel?
12 TM N and C are INTRACELLULAR
55
What is the structure of a bacterial K+ channel?
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
Who discovered the structure of the bacterial K channel?
Rod MacKinnon in 1998
57
What is the intracellular concentration of Cl-?
6 mM
58
What is the extracellular concentration of Cl-?
100 mM

BMS 242 - Core Phys/pharm (13 decks)

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