Membrane transport

Question 1

what are three methods of solute transport across cell membranes

Answer 1

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

Question 2

three examples of passive non carrier cell transport

Answer 2

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

Question 3

what is an example of carrier mediated transport

Answer 3

facilitated diffusion

Question 4

what are three methods of active solute transpoirt

Answer 4

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

Question 5

osmosis

Answer 5

the diffusion of water across a cell membrane

Question 6

what happens in secondary active transport

Answer 6

two simultaneous movement of two link substances across a cell membrane

Question 7

two types of secondary active transport

Answer 7

1. symport
2. antiport

Question 8

symport

Answer 8

coupled transport where the linked substances move in the same direction

Question 9

antiport

Answer 9

coupled transport where the two substances move in opposite directions

Question 10

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

Answer 10

solutes must be uncharged and hydrophobic

1. gasses
2. steroid hormones
3. anesthetics

Question 11

what is the driving force behind simple diffusion

Answer 11

the concentration gradient on either side of the cell membrane

Question 12

define all variables

Answer 12

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

T = temp in Kelvin (310 in humans)

X_i = intracellular fluid concentration of X

X₀ - extracellular fluid concentrationof X

Question 13

flux

Answer 13

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

Question 14

what is ficks first law of diffusion

Answer 14

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

Question 15

what two factors determine the amount of flux (diffusion)

Answer 15

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

Question 16

pores

Answer 16

intergra membrane proteins that for conduits that are always open

Question 17

channell

Answer 17

a gated pore that can be opened or closed

Question 18

describe the variables and what this equation means (3)

Answer 18

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

Question 19

describe the variables

Answer 19

• 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

Question 20

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

Answer 20

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

Question 21

primary active transport

Answer 21

solute movement against electrochemical gradiant that requires energy

Question 22

what are two sources of energy for primary active transport

Answer 22

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

Question 23

aquaporins

Answer 23

specialized water channels in the cell membrane

Question 24

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

Answer 24

1. RBCs
2. Renal proximal convoluted tubule

Question 25

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

Answer 25

cells in the renal collecting duct in response to ADH

Question 26

why is it impractical to measure the concentration of water

Answer 26

because there is too mich water to be accurate

Question 27

what is the relationship between solute concentration and water concentration

Answer 27

as solute concentration goes up water concentration goes down

Question 28

Gibbs-Donnan effect

Answer 28

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

Question 29

why must animal cells perform osmotic work

Answer 29

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

Question 30

when does osmotic work occur

Answer 30

during active transport with the Na/K pump

Question 31

osmolality

Answer 31

the total number of osmotically active solutes in a solution

Question 32

tonicity

Answer 32

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

Question 33

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

Answer 33

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

Question 34

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

Answer 34

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

Question 35

what happens to ECF and ICF with an infusion of NaCl

Answer 35

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

Question 36

why is epithelial transport important to homeostasis

Answer 36

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

Question 37

two places where epithelial transport takes place

Answer 37

1. apical membrane 2. basolateral membrane

Question 38

three parts of the apical membrane

Answer 38

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

Question 39

two parts of the basolateral membrane

Answer 39

1. serosal membrane 2. peritubular membrane

Question 40

apical membrane

Answer 40

the cell surfaces that face inward toward a lumen

Question 41

basolateral membrane

Answer 41

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

Question 42

two epithelial transport membrane

Answer 42

1. transcellular 2. paracellular

Question 43

transcellular epithelial transport

Answer 43

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

Question 44

paracellular epithelial transport

Answer 44

substances bypass the cell and cross epithelium through cell junctions

Question 45

two types of epithelial cell junctions

Answer 45

1. tight 2. leaky

Question 46

tight epithelia

Answer 46

cell junctions that maintain large ion concentration and osmotic gradients

Question 47

four examples of tight epithelia

Answer 47

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

Question 48

leaky epithelia

Answer 48

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

Question 49

two examples of leaky epithelia

Answer 49

1. small intestine 2. proximal convoluted tubule

Question 50

where are the Na/K pumps located

Answer 50

the basolateral membrane

Question 51

what is the function of the Na/K pumps

Answer 51

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

Question 52

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

Answer 52

it is recycled through the basolateral membrane via K channels

Question 53

flow

Answer 53

movement of matter

Question 54

flux

Answer 54

diffusion

Question 55

current

Answer 55

the flow of charged particles

Question 56

how can we increase current, flow, or flux

Answer 56

increase the driving force or decrease the resistance

Question 57

what is a simple way the body can regulate function

Answer 57

by regulation of current flux and flow

Question 58

T/F passive transport does not involve energy

Answer 58

false, passive transport releases energy

Question 59

in terms of energy, what direction does diffusion move

Answer 59

from high energy to low energy

Question 60

from an energy standpoint, what is a concentration gradient

Answer 60

store potential energy

Question 61

what is the largest energy expenditure in basal metabolism

Answer 61

the Na/K pump

Question 62

what is the driving force of simple diffusion

Answer 62

the chemical energy difference on each side of the concentration gradient

Question 63

resting membrane potential for a neuron

Answer 63

-70mV

Question 64

what is the charge inside the cell? why

Answer 64

negative, because the positive sodium is pumped out

Question 65

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

Answer 65

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

Question 66

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

Answer 66

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

Question 67

what direction does a negative delta G move

Answer 67

into the cell

Question 68

what direction does a positive delta G move

Answer 68

out of the cell

Question 69

what is the nerst equation and what is it used for

Answer 69

used to determine the equilibrium concentration of an ion

Question 70

what is used to determine the concentration gradient

Answer 70

the ideal gas law

Question 71

what is used to determine the electrochemical gradient

Answer 71

Question 72

why does a cell do osmotic work

Answer 72

to counter act donnan forces that move ions into the cell