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Physiology > Membrane Transport 1 > Flashcards

Membrane Transport 1 Flashcards

1
Q

What is the role of the membrane transport process?

A

Nutrients
Waste Rmvl
Ion Balance

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2
Q

Where is Na+ concentration higher, in the cytosol or outside the cell?

A

Extracellular. Cyt LO solt

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3
Q

What is the plasma membrane composed of?

A

Lipids, Proteins, and a tiny bit of carbohydrate

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4
Q

What are the 3 types of lipids in the membrane

A

Phospholipid
Cholesterol
Glycolipid

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5
Q

What is the head of the phospholipid?

A

Polar glycerol group

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6
Q

How can the structures in the membrane move?

A

Phospholipids rotate
Fatty acid chains bend
Fast Lateral diffusion in the same layer
Very rare and slow flip flop from one layer to the other

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7
Q

Is the composition of the two lipid layers always the same?

A

No. In fact it is usually different

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8
Q

What determines the ratio of lipids to proteins in the membrane?

A

The specific function of the cell

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9
Q

What are intrinsic membrane proteins?

A

Proteins that penetrate the bilayer and usually span it completely

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10
Q

What shape of the protein is usually spanning the membrane?

A

The alpha helix portion with the hydrophilic amino acids inside.

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11
Q

What is the basic description of an extrinsic or peripheral protein?

A

One that doesn’t penetrate the bilayer and it attached to one side or the other by weak ionic interactions.

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12
Q

What do extrinsic proteins usually attach to?

A

Membrane phospholipids or

Regions of intrinsic membrane proteins

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13
Q

Where are carbohydrates found when they are part of the membrane?

A

On the extracellular side

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14
Q

What percent of lipids are glycosolated?

A

10%

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15
Q

Are most extracellular proteins glycosolated?

A

Yes, almost all. A stark contrast compared to lipids

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16
Q

What is the role of the carbohydrate chains?

A

Cell recognition and receptor specificity

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17
Q

What are the 5 types of membrane transport?

A 
Simple diffusion
Facilitated diffusion
Primary active transport
Secondary active transport
Osmosis
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18
Q

What two methods of membrane transport are passive?

A

Simple diffusion

Facilitated diffusion

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19
Q

What makes them passive reactions?

A

The solutes are moving down the electrochemical gradient

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20
Q

For the active transport methods, where does the energy come from?

A

ATP hydrolysis

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21
Q

What are the three characteristic features of Carrier-Mediated Transport?

A

Saturation
Stereospecificity
Competition

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22
Q

What is the term that describes the point in time at which all binding sites of a receptor are occupied by the solute?

A

Transport Maximum (Tm)

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23
Q

Which characteristic of carrier mediated transport will allow the proteins to discriminate between D-glucose and L-glucose?

A

Stereospecificity….simple diffusion will not differentiate between isomers

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24
Q

What does Km stand for in a standard rate of solubility graph?

A

Solute concentration which gives half of the maximum transport rate

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25
Q

On a rate of solubility graph, which type of transport is represented by a line with a constant slope?

A

Simple diffusion.

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26
Q

What is the basic definition of simple diffusion?

A

Non-carrier mediated transport down an electrochemical gradient

27
Q

What determines the rate of simple diffusion for a non-ionic solute?

A

The concentration gradient of the solution on each side of the membrane

28
Q

What determines the rate of simple diffusion for electrolytic solutes?

A

The concentration (chemical) and electrical gradient….in other words the electrochemical (combined) gradient.

29
Q

In terms even more basic then electrochemical gradient what causes diffusion to proceed?

A

Random thermal movement of molecules

30
Q

What is the term for the rate of net diffusion of solutes across the membrane?

A

Flux (J)

31
Q

In what terms is Flux expressed?

A

Amount of solute moving across a unit area of membrane per unit of time

32
Q

What are the 5 primary variable that effect Flux?

A

The concentration gradient across the membrane [C1-C2]
The thickness of the membrane (Constant in our case)
Lipid solubility of the solute
Diffusion Coefficient
Permeability of the Solute

33
Q

The variable that represents lipid solubility is called what?

A

K, the oil water partition coefficient

34
Q

Please write the equation for K

A

K = (Concentration in Oil Phase)/(Concentration in Water Phase)

35
Q

For solutes that a very lipid soluble will the K value be higher or lower?

A

Higher

36
Q

What is the variable that represents the diffusion coefficient?

A

D

37
Q

How does the diffusion coefficient of a solute relate to its size and the viscosity of the medium?

A

It is INVERSELY correlated with the radius of the solute and the viscosity of the medium.

38
Q

So which will move across the membrane faster? A large solute in a viscous medium or a small solute in a non-viscous medium?

A

The small solute in the less viscous medium?

39
Q

What is the permeability of a solute?

A

Its a combination of several other factors combined into a term that calculated the permeability of the solute in units of cm/sec

40
Q

What is the formula for Permeability (P)?

A

P = KD/Membrane Thickness

41
Q

What is the formula for Flux for an uncharged solute diffusing from a region of high concentration to low?

A

J = P[C1-C2]

42
Q

Once C1=C2 is there still diffusion of the solute across the membrane?

A

Yes, but there is no net diffusion. It has reached dynamic equilibrium

43
Q

How would you determine the total amount of solute diffusing across the membrane of the entire cell?

A

By multiplying Flux (J) times the area of the plasma membrane

44
Q

What does the term diffusion trapping refer to?

A

The diffusion of weak acids across the membrane.

45
Q

How can weak acids get trapped?

A

the un-dissociated weak acid can diffuse because it has no charge. However when it crosses the membrane and the pH changes it can then dissociate and become trapped on one side of the membrane

46
Q

How can lipid insoluble substances get across the membrane?

A

Facilitated diffusion

47
Q

How does the rate of facilitated diffusion compare to simple diffusion?

A

Facilitated is much faster

48
Q

What can halt facilitated diffusion compared to simple?

A

Saturation…simple diffusion will continue as long as the gradient exists

49
Q

Besides saturation, how can facilitated diffusion be inhibited?

A

Competitive binding

50
Q

Which is faster for transporting ions across the membrane: Ion channels or Facilitated Diffusion?

A

Ion channels are 1000x faster

51
Q

Which can be regulated? Ion channels or Facilitated Diffusion?

A

Ion channels

52
Q

What separates Primary Active Transport from Secondary Active Transport?

A

Primary active transport of a solute is directly linked to ATP hydrolysis

53
Q

What enzyme uses 30% of a cell’s energy to create intentional Ion imbalances?

A

Na/K ATPase (Sodium Potassium Pump)

54
Q

What can inhibit the pump?

A

Cardiac Glycosides: Ouabain & Digoxin

55
Q

What is the ratio of ions moved for each ATP used?

A

3 Balls
2 StriKes

3 Sodium ions are ejected
2 Potassium ions are brought in

56
Q

By pumping out three Na and taking in only 2 K what does the pump create besides a chemical imbalance?

A

A small negative charge inside the cell

57
Q

Where is the Ca2+ ion pump located?

A

Mainly in the sarcoplamic reticulum, mitochondria, and plaslemma membranes

58
Q

Where is the H+/K+ Pump found?

A

Gastric parietal cells of the stomach and in the kidney

59
Q

If its not tied directly to ATP hydrolysis, how does secondary transport move solutes upstream?

A

It relies on the electrochemical gradients created by primary active transport

60
Q

What are the 2 types of secondary active transport?

A

Symport/Co-Transport

Antiport/Exhange

61
Q

What is symporting?

A

All solutes move in the same direction across the membrane

62
Q

What is an example of a symporter?

A

Na+ coupled to D-Glucose in the intestinal epithelium

63
Q

What is an antiporter?

A

Solutes are moving in opposite directions across the membrane. So as sodium moves into the cell, the solute will leave the cell against its own chemical gradient

64
Q

What is an example of an antiporter?

A

Ca2+/Na+ exchange

Physiology (13 decks)

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