1 2 Membrane Transport: Passive and Active

Question 1

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

Answer 1

gasses like oxygen and carbon dioxide

Question 2

lipid bilayer is made of

Answer 2

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

Question 3

e.g. of intrinsic membrane proteins

Answer 3

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

Question 4

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

Answer 4

hydrophlic

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

Question 5

movement in the bilayer (2 examples)

Answer 5

axial rotation

lateral diffusion

Question 6

e.g. extrinsic/peripheral proteins

Answer 6

proteins of the cytoskeleton

Question 7

extrinsic protein features

Answer 7

do not span the membrane

attachment occurs via ionic interactions to membrane phospholipids or intrinsic proteins

Question 8

carbohydrates are on the ___ surface of the membrane

Answer 8

extracellular

Question 9

role of monosaccharides on the PM

Answer 9

cell recognition/determining receptor specificity

Question 10

passive transport: definition, examples

Answer 10

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

Question 11

active transport: definition, examples

Answer 11

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

Question 12

all transport except for ____ needs a carrier molecule

Answer 12

simple diffusion

Question 13

3 characteristics of carrier mediated transport

Answer 13

saturation
stereospecificity
competition

Question 14

saturation

Answer 14

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

Question 15

which type of diffusion does not care about stereospecificity

Answer 15

simple diffusion

Question 16

competition

Answer 16

structurally similar solutes compete for the same site

Question 17

is simple diffusion saturable?

Answer 17

no

Question 18

Km =

Answer 18

solute concentration which gives half the maximal transport rate

Question 19

simple diffusion

Answer 19

non-carrier mediated transport down an electrochemical gradient

Question 20

FLUX, J

Answer 20

the rate of net diffusion of solute molecules

the amount of solute moving across a unit area of membrane per unit of time

Question 21

flux depends on 5 things

Answer 21

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

Question 22

oil water partition coefficient (K)

Answer 22

oil / water

the higher it is, the greater the lipid solubility

Question 23

diffusion coefficient (D)

Answer 23

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

Question 24

permeability

Answer 24

P = KD / membrane thickness

Question 25

flux formula

Answer 25

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

Question 26

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

Answer 26

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

Question 27

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

Answer 27

no net flux

Question 28

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

Answer 28

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

Question 29

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

Answer 29

lipid solubility and molecular size

Question 30

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

Answer 30

smaller

Question 31

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

Answer 31

the un-dissociated form | they can get "trapped" if the pH changes and they dissociate

Question 32

facilitated diffusion

Answer 32

how lipid insoluble stuff gets across the membrane without using energy

Question 33

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

Answer 33

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

Question 34

ion channels (4 things)

Answer 34

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

Question 35

facilitated diffusion is for the movement of

Answer 35

sugars and amino acids

Question 36

active transport

Answer 36

requires energy | moves things against a chemical or electrochemical gradient

Question 37

primary active transport

Answer 37

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

Question 38

inhibitors of the sodium pump (2)

Answer 38

cardiac glycosides: ouabain and digoxin *these also inhibit secondary active transport*

Question 39

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

Answer 39

3 Na out | 2 K in

Question 40

two other examples of primary active transport

Answer 40

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

Question 41

secondary active transport

Answer 41

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

Question 42

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

Answer 42

Na+

Question 43

there are two types of secondary active transport

Answer 43

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

Question 44

symport/co-transport

Answer 44

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

Question 45

antiport/countertransport/exchange

Answer 45

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)

Question 46

aquaporins

Answer 46

the holes water travels through across a membrane

Question 47

osmosis

Answer 47

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

Question 48

_____ ______ is the driving force for osmosis

Answer 48

osmotic pressure

Question 49

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

Answer 49

hydrostatic pressure (column of water)

Question 50

osmolarity

Answer 50

the number of solute particles present in a solution

Question 51

osmoles

Answer 51

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

Question 52

concentrated solutions have ____ osmolarity

Answer 52

higher

Question 53

concentrated solutions have ____ osmotic pressures than dilute solutions

Answer 53

higher

Question 54

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

Answer 54

lower to higher

Question 55

osmotic pressure is proportional to _____ concentration

Answer 55

solute

Question 56

osmotic pressure depends on total _____ of the solution

Answer 56

osmolarity

Question 57

iso-osmotic solution

Answer 57

isotonic - no swelling or shrinkage occurs

Question 58

hypotonic solution

Answer 58

surrounding environment is less concentrated, so water swells into the more concentrated cell and swells it (more dilute solutions cause bursting)

Question 59

hypertonic solution

Answer 59

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

Question 60

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

Answer 60

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