1 2 Membrane Transport: Passive and Active Flashcards Preview

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Flashcards in 1 2 Membrane Transport: Passive and Active Deck (60):
1

___, like ___ and ___ are highly lipid soluble and easily pass though the PM

gasses like oxygen and carbon dioxide

2

lipid bilayer is made of

phospholipids with hydrophlic heads and hydrophobic fatty acid tails (the lipid part is in the middle)

3

e.g. of intrinsic membrane proteins

ion channels, water channels, transporters, hormone receptors, cell surface antigens

4

intrinsic membrane proteins have _____ amino acid regions which are tucked within the alpha helix

hydrophlic
these are tucked inside since they are running through a hydrophobic region (the membrane)

5

movement in the bilayer (2 examples)

axial rotation
lateral diffusion

6

e.g. extrinsic/peripheral proteins

proteins of the cytoskeleton

7

extrinsic protein features

do not span the membrane
attachment occurs via ionic interactions to membrane phospholipids or intrinsic proteins

8

carbohydrates are on the ___ surface of the membrane

extracellular

9

role of monosaccharides on the PM

cell recognition/determining receptor specificity

10

passive transport: definition, examples

substance is transported down its electrochemical gradient and no energy is required
simple diffusion, facilitated diffusion

11

active transport: definition, examples

substance is transported against its electrochemical gradient and requires energy (ATP)
primary active transport, secondary active transport

12

all transport except for ____ needs a carrier molecule

simple diffusion

13

3 characteristics of carrier mediated transport

saturation
stereospecificity
competition

14

saturation

limited number of binding sites on carrier proteins (transport maximum or Tm)

15

which type of diffusion does not care about stereospecificity

simple diffusion

16

competition

structurally similar solutes compete for the same site

17

is simple diffusion saturable?

no

18

Km =

solute concentration which gives half the maximal transport rate

19

simple diffusion

non-carrier mediated transport down an electrochemical gradient

20

FLUX, J

the rate of net diffusion of solute molecules
the amount of solute moving across a unit area of membrane per unit of time

21

flux depends on 5 things

concentration gradient across the membrane
thickness of the membrane
lipid solubility of the solute
diffusion coefficient
permeability of a solute

22

oil water partition coefficient (K)

oil / water
the higher it is, the greater the lipid solubility

23

diffusion coefficient (D)

the larger the molecule and more viscous the medium, the lower the D

24

permeability

P = KD / membrane thickness

25

flux formula

J = P (C1-C2)
permeability constant * diff in conc of solute across the membrane

26

in the flux equation, as long as C1 > C2, that means

there is net movement of solute from side 1 to side 2 of the PM

27

once equilibrium has been reached, this is considered ___ ___ flux of solute

no net flux

28

formula for the total amount of solute diffusing across an entire membrane into a cell

flux formula times the area of the membrane
= PA (C1-C2)

29

the rate at which an uncharged solute (non-electrolyte) diffuses across the cell membrane is dictated by its ____ and _____

lipid solubility and molecular size

30

are bigger or smaller molecules faster at diffusing through the PM?

smaller

31

which form of a weak acid/base can diffuse across the membrane?

the un-dissociated form

(they can get "trapped" if the pH changes and they dissociate)

32

facilitated diffusion

how lipid insoluble stuff gets across the membrane without using energy

33

facilitated diffusion is different from simple diffusion b/c (4 things)

-allows much more solute to be transported
-is saturable
-is solute specific
-competition is involved

34

ion channels (4 things)

-passive (driven by electrochemical gradient)
-regulated (channels open and close)
-three magnitudes faster than facilitated diffusion
-for electrical signaling and secretory processes

35

facilitated diffusion is for the movement of

sugars and amino acids

36

active transport

requires energy
moves things against a chemical or electrochemical gradient

37

primary active transport

directly coupled to an energy producing reaction
i.e. sodium pump (Na/K ATPase)

38

inhibitors of the sodium pump (2)

cardiac glycosides: ouabain and digoxin

*these also inhibit secondary active transport*

39

for each molecule of ATP, ___ Na ions are pumped out and ____ K ions are pumped in

3 Na out
2 K in

40

two other examples of primary active transport

Ca2+ ATPase - pumps Ca2+ out of cytoplasm
H+-K+ ATPase

41

secondary active transport

NOT directly coupled to an energy producing reaction but instead depends on the primary active transport of sodium

42

secondary active transport depends on the primary active transport of this ion

Na+

43

there are two types of secondary active transport

1/ symport or co-transport
2/ antiport/countertransport/exchange

44

symport/co-transport

all solutes move in the same direction across the cell membrane

the uphill solute moves in the same direction as sodium, so INTO THE CELL

45

antiport/countertransport/exchange

uphill solute moves in the opposite direction to the sodium

sodium moves into the cell down its gradient
the solute here moves out of the cell AGAINST its gradient (the solute conc is high outside and low inside)

46

aquaporins

the holes water travels through across a membrane

47

osmosis

movement of water across a semi-permeable membrane as a result of the difference in the concentration of particles of a solute that is unable to pass across the membrane

water moves from the solution with the lowest to the solution with the highest concentration of particles

48

_____ ______ is the driving force for osmosis

osmotic pressure

49

in osmosis, the movement of water continues until the ____ pressure opposes the osmotic pressure

hydrostatic pressure (column of water)

50

osmolarity

the number of solute particles present in a solution

51

osmoles

= n x moles
n = number of particles from each molecule

52

concentrated solutions have ____ osmolarity

higher

53

concentrated solutions have ____ osmotic pressures than dilute solutions

higher

54

water moves from ____ to _____ osmotic pressures across a semipermeable membrane

lower to higher

55

osmotic pressure is proportional to _____ concentration

solute

56

osmotic pressure depends on total _____ of the solution

osmolarity

57

iso-osmotic solution

isotonic - no swelling or shrinkage occurs

58

hypotonic solution

surrounding environment is less concentrated, so water swells into the more concentrated cell and swells it

(more dilute solutions cause bursting)

59

hypertonic solution

surrounding environment is more concentrated, so water inside the cell rushes out, causing the cell to shrink and shrivel

60

what happens to a cell when the sodium pump is not working?

Na+ is not pumped out, so water rushes in, causing the cell to swell