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BMS 752 (Medical Physiology) > Membrane transport > Flashcards

Flashcards in Membrane transport Deck (72):
1

what are three methods of solute transport across cell membranes

  1. passive/non-carrier mediated
  2. passive/carrier mediated
  3. active

 

2

three examples of passive non carrier cell transport

  1. simple diffusion across the cell membrane
  2. simple diffusion through pores
  3. simple diffusion through gated channels

 

3

what is an example of carrier mediated transport

facilitated diffusion

4

what are three methods of active solute transpoirt

  1. active transport requiring ATP
  2. active transport using energy from redox reactions
  3. secondary active transport

 

5

osmosis

the diffusion of water across a cell membrane

6

what happens in secondary active transport

two simultaneous movement of two link substances across a cell membrane

7

two types of secondary active transport

  1. symport
  2. antiport

 

8

symport

coupled transport where the linked substances move in the same direction

9

antiport

coupled transport where the two substances move in opposite directions

10

what types of solutes are capable of simple diffusion? examples (3)

solutes must be uncharged and hydrophobic

  1. gasses
  2. steroid hormones
  3. anesthetics

 

11

what is the driving force behind simple diffusion

the concentration gradient on either side of the cell membrane

12

define all variables

Q image thumb

R = ideal gas constant (.002kcal/mol)

T = temp in Kelvin (310 in humans)

Xi = intracellular fluid concentration of X

X0 - extracellular fluid concentrationof X

13

flux

the number of moles of a solute that cross a unit area of a membrane per unit of time (moles/cm2 * s)

14

what is ficks first law of diffusion

flux will move from areas of high concentration to areas of low concentration

15

what two factors determine the amount of flux (diffusion)

  1. permeability of the membrane to X
  2. magnitude of the gradient fo X across the membrane

 

 

16

pores

intergra membrane proteins that for conduits that are always open

17

channell

a gated pore that can be opened or closed

18

describe the variables and what this equation means (3)

Q image thumb

  1. the electrochemical difference is the the driving force behind passive diffusion
  2. the electrochemical difference is the sum of the chemical energy difference and electrical energy difference
  3. z = valence of the ion, F = .023kcal/mol *mV, psi1 - psi0 = the membrane potential

19

describe the variables

Q image thumb

  • E si the equilibrium potential for the ion
  • R is the ideal gas constant
  • T is the temperature in kelvin
  • Xi is the ICF solute concentration
  • Xo is the ECF solute concentration
  • zx is the valence of electron x
  • F is Farraday constant

 

20

what are six steps in passive membrane transport through integral membrane proteins

  1. the carrier protein is open
  2. x enters the protein and bind to the binding site
  3. outer gate closes and x becomes trapped in the protein
  4. inner gate opens with x still bound
  5. X exits the inside of the cell
  6. the outer gate closes, occluding the empty binding site

 

21

primary active transport

solute movement against electrochemical gradiant that requires energy

22

what are two sources of energy for primary active transport

  1. ATP hydrolysis
  2. directly from a primary metabolic reaction

 

23

aquaporins

specialized water channels in the cell membrane

24

what are two types of cells that always have aquaporins (AQP1)

  1. RBCs
  2. Renal proximal convoluted tubule

 

25

what is an example of a cell that places aquaporins based on hormonal control

cells in the renal collecting duct in response to ADH

26

why is it impractical to measure the concentration of water

because there is too mich water to be accurate

27

what is the relationship between solute concentration and water concentration

as solute concentration goes up water concentration goes down

28

Gibbs-Donnan effect

the effect of a charged membrane on charged particles, leading to unequal distribution of ions across the membrane

29

why must animal cells perform osmotic work

because animal cells swell rather than increase osmotic pressure as water enters and must pump water out of the cell

30

when does osmotic work occur

during active transport with the Na/K pump

31

osmolality

the total number of osmotically active solutes in a solution

32

tonicity

the comparision of effective osmolalities between two solutions seperated by a membrane

33

what happens to the ECF and ICF with an infusion of isotonic saline

ECF increases with no increase in ICF because there is no change in osmolality

34

what happens to ECF and ICF with an infustion of solute free water

the ECF experiences an intial decrease in osmolality, causing solutes to diffuse out of the ICF to restore equalibrium

35

what happens to ECF and ICF with an infusion of NaCl

ECF experiences an increase in osmolality, causing solute to difuse into the ICF 

36

why is epithelial transport important to homeostasis

it controls the composition of interstitual fluid through membrane transport between the body and environment

37

two places where epithelial transport takes place

  1. apical membrane
  2. basolateral membrane

 

38

three parts of the apical membrane

  1. brush border
  2. mucosal membrane
  3. luminal membrane

 

39

two parts of the basolateral membrane

  1. serosal membrane
  2. peritubular membrane

 

40

apical membrane

the cell surfaces that face inward toward a lumen 

41

basolateral membrane

the epitheial cells surfaces that face adjacent cells or toward the underlying connective tissue

42

two epithelial transport membrane

  1. transcellular
  2. paracellular

 

43

transcellular epithelial transport

substances crosses the cell by going through the apical and then basolateral membranes

44

paracellular epithelial transport

substances bypass the cell and cross epithelium through cell junctions

45

two types of epithelial cell junctions

  1. tight
  2. leaky

 

46

tight epithelia

cell junctions that maintain large ion concentration and osmotic gradients

47

four examples of tight epithelia

  1. distal portion of the distal convoluted tubule
  2. collecting duct
  3. large intestine
  4. urinary bladder

 

48

leaky epithelia

cell junctions cannot maintain large gradients and are used for bulk transport of solute and water

49

two examples of leaky epithelia

  1. small intestine
  2. proximal convoluted tubule

 

50

where are the Na/K pumps located

the basolateral membrane

51

what is the function of the Na/K pumps

the keep a large inward Na gradient to drive secondary active transport

52

what happens to most of the K brought into the cell from the Na/K pump

it is recycled through the basolateral membrane via K channels

53

flow

movement of matter

54

flux

diffusion

55

current

the flow of charged particles

56

how can we increase current, flow, or flux

increase the driving force or decrease the resistance

57

what is a simple way the body can regulate function

by regulation of current flux and flow

58

T/F passive transport does not involve energy

false, passive transport releases energy

59

in terms of energy, what direction does diffusion move

from high energy to low energy

60

from an energy standpoint, what is a concentration gradient

store potential energy

61

what is the largest energy expenditure in basal metabolism

the Na/K pump

62

what is the driving force of simple diffusion

the chemical energy difference on each side of the concentration gradient

63

resting membrane potential for a neuron

-70mV

64

what is the charge inside the cell? why

negative, because the positive sodium is pumped out

65

why is the resting membrane potential of a cell relevant to diffusion

because it is negative, so positive ions are pulled into the cell, and the concentration pushes sodium into the cell

66

based on chemical energy and concentration, where will potassium be driven in the cell

it will depend on if the chemical energy is overcome by potential energy of the concentration gradient

67

what direction does a negative delta G move

into the cell

68

what direction does a positive delta G move

out of the cell

69

what is the nerst equation and what is it used for

used to determine the equilibrium concentration of an ion

A image thumb
70

what is used to determine the concentration gradient

the ideal gas law

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71

what is used to determine the electrochemical gradient

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72

why does a cell do osmotic work

to counter act donnan forces that move ions into the cell