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Physiology 2410 > Lecture 4- Transport across the cell membrane > Flashcards

Lecture 4- Transport across the cell membrane Flashcards

1
Q

what is diffusion?

A

process of moving solute molecules away from an area of high concentration towards area of low concentration (down the concentration gradient)

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2
Q

what is passive diffusion?

A

no external energy, just kinetic energy of molecules

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3
Q

when does diffusion stop?

A

when equilibrium is reached

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4
Q

when is diffusion fast? (3)

A

over short distances
high temperature
faster for small molecules

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5
Q

when is diffusion slow? (2)

A

over long distances
across a membrane

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6
Q

how do you calculate the time taken to get from one point to another in the membrane?

A

distance squared (if its 2 miles to get there it will be 2^2 therefore 4 miles, this is because molecules move randomly)

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7
Q

what is simple diffusion?

A

no membrane
diffusion is fast
(ex. small gases like O2)

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8
Q

how does a semipermeable membrane work?

A

allows selected solutes to pass, but more slowly (does not allow some solutes to pass)

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9
Q

what does the cell membrane allow to pass through it?

A

hydrophobic
non- polar
small uncharged polar molecules

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10
Q

are fat soluble molecules able to pass through the cell membrane?

A

yes, as well as, steroids, lipids, oxygen and carbon dioxide

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11
Q

is water able to pass through cell membranes?

A

yes, because its so small it can slip through but there is also some resistance against water
there are also water channels in the cell membrane

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12
Q

what is unable to pass through the cell membrane?

A

large molecules
uncharged molecules
polar molecules

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13
Q

what are the 5 rules of diffusion of solute across cell membranes?

A
  1. permeability across cell membrane
  2. concentration gradient
  3. surface area
  4. temperature
  5. composition of membrane/ lipid layer
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14
Q

what does the rule mean about permeability across cell membrane?

A

size
lipid solubility

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15
Q

what does lipid solubility describe?

A

polar: wont go through
non- polar: goes through but not easily
VERY non- polar: goes through easily

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16
Q

what does the composition of membrane rule mean?

A

types of phospholipids and sphingolipids
presence of cholesterol
simple bilayer or bilayer filled with proteins

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17
Q

why would the presence of cholesterol affect diffusion across a cell membrane?

A

if theres lots of cholesterol, its harder for a solute to diffuse across because cholesterol plugs all the spaces between tails

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18
Q

what are ficks 5 laws of diffusion?

A

lipid solubility
molecular size
concentration gradient
membrane surface area
composition of lipid layer

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19
Q

what will happen to a small polar molecule?

A

it will diffuse

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20
Q

why might some drugs have low bioavaliability?

A

poor solubility

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21
Q

why might some drugs be toxic at useful doses?

A

because some drugs like the cancer drugs (kill cancer cells) direct one thing in the body, so you need to take a higher dosage. the higher dosage can be toxic. this only happens with drugs that are targeted to a specific cell type.

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22
Q

what is liposomal drug delivery and what does it do?

A

selectively deliver their payload to the diseased site through passive and/or active targeting. in doing this it makes the drug not toxic!

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23
Q

how does liposomal drug delivery work?

A

drug molecules are implanted into the aqueous core of the liposome and turn smaller into micro- crystals in there. Over time the bilayer deteriorates and the liposomes release their inner drug contents.

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24
Q

what is a lipid nanoparticle?

A

liposome that uses the inner phospholipid bilayer to surround the drug when inside the cell

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25
Q

what are mRNA-LNPs used for?

A

mRNA-LNPs are used as delivery agents encapsulating lipophilic and hydrophilic medication because of their high targeting qualities through ligand functionalization

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26
Q

how much of the body’s total water volume is in the intracellular and extracellular fluid?

A

intracellular: 2/3
extracellular: 1/3

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27
Q

what does the extracellular fluid consist of? (2)

A

interstitial fluid (makes up 75% of ECF)
plasma (makes up 25% of ECF)

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28
Q

what is chemical disequilibrium?

A

chemical disequilibrium- more solutes are concentrated in either one body compartment or another which creates chemical disequilibrium.

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29
Q

what is electrical disequilibrium?

A

electrical disequilibrium is due to ionic imbalance from cations and anions not being equally distributed throughout the body.

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30
Q

what is osmotic equilibrium?

A

osmotic equilibrium is when the concentrations are equal on both sides of the membrane. This results in zero osmotic pressure and non net movement of water

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31
Q

what is osmosis?

A

diffusion of water

32
Q

how does water diffuse?

A

down its concentration gradient

33
Q

what can the movement of water result in?

A

pressure

34
Q

what has the highest concentration of water?

A

pure water

35
Q

how does waters concentration gradient work?

A

where theres more solutes thats where the water will go

36
Q

what are the normal physiological concentrations of salts in mammalian cells (extracellular and intracellular)

A

extracellular:
K+ 5 mM
Na+ 145 mM
Cl- 108 mM
Ca++ 1 mM

intracellular:
K+ 150 mM
Na+ 15 mM
Cl- 5 mM
Ca++ 0.0001 mM

37
Q

in general, what is the healthy amount of milliosmoles (mOsm) per kilogram of water for a person

A

290 mOsm

38
Q

if there is 1M of glucose how many OsM will we have?

A

1 Osm

39
Q

if we have 1M of NaCl how many OsM will we have?

A

2 Osm
because NaCl is technically 2 molecules so we calculate it like that even though in ionic state theyre together)

40
Q

what does changing osmolarity of the extracellular solution cause?

A

redistribution of water and some solutes in cells
causes cells to shrink or swell

41
Q

if a solution is hypertonic, what does that mean?

A

higher solute concentration outside the cell
cells will shrink

42
Q

if a solution is isotonic what does that mean?

A

cells dont change size and everyones happy
(ecf may be higher than inside the cell but if its at 290 mOsM that is perfectly where they want to be)

43
Q

if a solution is hypotonic, what does that mean?

A

concentration of solute is higher inside the cell, thus water enters the cell and cell swells

44
Q

what is the difference between osmolarity and tonicity?

A

osmolarity:
-describes the number of solute molecules in a cell (units of Osm)
-compares any two solutions
-doesn’t always tell if a cell swells or shrinks
tonicity:
-describes whether a cell changes volume (no units)
-compares solution to a cells intracellular solution
-tells if a cell swells or shrinks

45
Q

what does osmolarity measure the concentration of?

A

concentration of penetrating and non- penetrating solutes

46
Q

what does tonicity measure?

A

only non- penetrating

47
Q

what are examples of penetrating molecules?

A

urea, glycerol, ethanol
(small polar and non-polar molecules)

48
Q

what are examples of non- penetrating molecules?

A

Na+, glucose, amino acids
(ions and larger polar molecules)

49
Q

are normal physiological intracellular solutes penetrating or non- penetrating?

A

non- penetrating

50
Q

are hypoosmotic solutions always hypotonic?

A

yes

51
Q

are hyperosmotic solutions always hypertonic?

A

not necessarily

52
Q

what do you do if you are trying to determine tonicity and penetrating solutes are present?

A

disregard their concentrations (water will flow into the compartment that contains the higher concentration of non- penetrating solutes)

53
Q

what are channel proteins?

A

water filled pore that can open to both sides

54
Q

what are the two types of channel proteins?

A

gated channels
open channels

55
Q

what is the big difference between carrier proteins and channel proteins?

A

carrier proteins never form an open channel between the two sides of the membrane

56
Q

carrier proteins have uniport carriers, symport carriers and antiport carriers, what do they all do?

A

uniport: one direction with one molecule at a time
symport: one direction with two molecules at a time
antiport: moves two molecules but in different directions

57
Q

how do carrier proteins work?

A

molecule enters carrier protein into its own specific spot
carrier protein closes
carrier protein opens to the icf to release molecule

58
Q

in terms of energy requirements there are 3 categories of carrier proteins, what are they?

A

facilitated diffusion
primary active transport
secondary active transport

59
Q

what is facilitated diffusion?

A

moves a solute molecule across the cell membrane with the help of a carrier protein

60
Q

what is unique about facilitated diffusion?

A

does not require energy otehr than the concentration gradient, therefore does not require ATP or other solutes.

61
Q

whats another name for facilitated diffusion?

A

passive transport

62
Q

can passive transport/ facilitated diffusion go against a concentration gradient? what does it mean

A

no, therefore, molecules only move in one direction down their concentration gradient.
facilitated diffusion is an example of uniport carrier

63
Q

what is an examples of facilitated diffusion?

A

GLUT protein (transporter that transports glucose)

64
Q

how does the cell never allow glucose levels to be at equilibrium?

A

convert imported glucose into glucose 6- phosphate
keeps intracellular glucose concentrations low

65
Q

why is it called primary active transport?

A

directly uses chemical energy (ATP) to transport all solutes across a membrane against their concentration gradient

66
Q

what can primary active transport also be called?

A

pumps

67
Q

what is an example of primary active transport?

A

Na+/ K+ ATPase

68
Q

how does Na+/ K+ ATPase work?

A

for every 2 K+ and 3 Na+ it uses 1 ATP

69
Q

is Na+/ K+ ATPase a channel?

A

NO

70
Q

what is secondary active transport?

A

active transport
does not directly utilize ATP as a source of energy, moves one molecule down its gradient while simultaneously moving another molecule against its concentration gradient. it takes the energy from moving one molecule down its gradient

71
Q

what is an example of secondary active transport protein?

A

SGLT- protein
sodium glucose active transport protein

72
Q

in SGLT- protein transport, which molecule is moving against its concentration gradient?

A

glucose is high inside the cell, therefore, the sodium binds to the SGLT- protein first which makes a spot for the glucose to bind

73
Q

what kind of transport does epithelial transport use?

A

facilitated diffusion
primary active transport
secondary active transport

74
Q

what is the first type of transport epithelial transport uses?

A

primary active transport (active transport)
Na+/ K+ ATPase maintains Na+ gradient

75
Q

what is the second type of transport epithelial transport uses?

A

secondary active transport (active transport)
Na+ gradient is used to get glucose transported into the cell against the concentration gradient

76
Q

what is the third type of transport epithelial transport uses?

A

facilitated diffusion
if glucose gets way too high in the cell from all the glucose going against its concentration gradient in secondary active transport it can leave through the GLUT transporter

Physiology 2410 (21 decks)

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