membrane transport

Question 1

ions found mostly in extraceullar fluid

Answer 1

Na and Cl

Question 2

ions found mostly in cells

Answer 2

K and PO43+

Question 3

rate of solute movement across a membrane

Answer 3

P x C

where P is the permeability coefficient and C is the concentration gradient

Question 4

hydrophobic molecules

Answer 4

diffuse easily across the membrane

O2, CO2, N2, steroid hormones

Question 5

small uncharged polar molecules

Answer 5

kinda go through the plasma membrane

water, urea, glycerol, NH3

Question 6

large uncharged polar molecules

Answer 6

mostly don’t go through the membrane

glucose and sucrose

Question 7

ions

Answer 7

don’t go through the plasma membrane at all

protons, sodium, HCO3-, K+, Ca2+, Cl-, Mg2+

Question 8

osmolarity

Answer 8

the concentration of everything but water

Question 9

why is osmolarity sometimes hard too calculate

Answer 9

• Depends on how much stuff dissociates

- Osmolaritty of proteins and macromolecules hard to predict depends on dissociation

Question 10

osmolarity of intracellular fluid

Answer 10

• Osmolarty of intracellular fluid is 300mOsmol/L

Question 11

aquaporins

Answer 11

channel allowing water to move

allows bidirectional movement

Question 12

tonicity

Answer 12

whether a cell swells or shrinks due to osmosis

Question 13

isotonic

Answer 13

cell stays the same size

Question 14

hypertonic

Answer 14

has more solutes so the cell shrinks

Question 15

hypotonic

Answer 15

has less solute so the cell swells or bursts

Question 16

iso osmolar

Answer 16

same osmotic value

Question 17

why is iso-osmolar not the same as isotonic

Answer 17

solutes can move through membrane as well

Question 18

when is iso osmolar the same as isotonic

Answer 18

when dealing with solutes that don’t move across the membrane

Question 19

channel and transporter mediated transport is powered by

Answer 19

concentration gradient

Question 20

pump mediated transport is powered by

Answer 20

ATP

Question 21

pores and channels

Answer 21

• Water filled pores and channels increase permeability
  
  • Pores and channels can be selective eg. Aquaporin for water
  • Channels are gated pores allow control of permeability

Question 22

channels are different to pores because

Answer 22

• Channels are gated pores allow control of permeability

Question 23

3 types of gated channels

Answer 23

mechanically gated, ligand gated, voltage gated

Question 24

mechanically gated channels

Answer 24

shut when there is no tension

Question 25

ligand gated channels

Answer 25

○ Chemical molecule - ligand - opens the channels | ○ Can be extracellular or intracellular ligand

Question 26

voltage gated channels

Answer 26

○ Most cells are negative on the inside and positive on the outside ○ When the voltage changes the channels open

Question 27

carrier proteins and transport proteins

Answer 27

- Facilitated diffusion - Conformational change -> transport - Energy from concentration gradient

Question 28

uriporters

Answer 28

○ Transport a signle solute from one side of the membrane to another

Question 29

- Co-transporters

Answer 29

○ Transfer of one solute depends on the simultaneous transport of a second solute (coupled transport)

Question 30

2 types of co transporters

Answer 30

○ Symporters § Transfer second solute in the same direction as the first ○ Antiporters § Transfer the second molecule in the opposite direction tto the first

Question 31

SGLT1

Answer 31

- Sodium-dependant glucose transporter - Na+ and glucose transport - Symporter

Question 32

Active transport - pumps

Answer 32

- Pumps use the chemical potential energy to pump molecules up hill against their concentration gradient - The pump is effectively a carrier being forced to operate in reverse (both are called transporters/facilitated diffusion)

Question 33

ATP-binding cassette transporters - ABCs

Answer 33

- bind specific molecules and use ATP energy to transport them across phospholipid bilayers - Huge superfamily (many transporters = many target molecules)

Question 34

ABC transporter example

Answer 34

ABCA/ABCG - exports cholesterol out of cells

Question 35

The Na+/K+ pump

Answer 35

- Uses ATP - Antiporter - All cells have this pump and it uses 33% of it's cellular energy

Question 36

how many ions does the NA/K pump transport

Answer 36

- Pumps 3x Na+ put and 2x K+ in per cycle | - Uses 1xATP molecule

Question 37

electrical effect of Na/K pump

Answer 37

- Electrogenic - net movement of +ve charge out of cell

Question 38

inside of the cell is charged

Answer 38

negatively

Question 39

secondary active transport

Answer 39

establishing the Na/K gradient and using it to pump other things in and out of the cell

Question 40

example of secondary active transport

Answer 40

SGLT1 symporter of Na and glucose | allows glucose uptake

Question 41

2 types of exocytosis

Answer 41

constitutive and regulated

Question 42

constitutive exocytosis

Answer 42

§ Produce a protein and put it in a vessicle and it has unregulated membrane fusion

Question 43

regulated exocytosis

Answer 43

§ Regulated membrane fusion

Question 44

endocytosis

Answer 44

○ Big things (phagocytosis), little things (pinocytosis) | ○ Can be highly specific (receptor mediated)

Question 45

what products the vesicle

Answer 45

coat protein - clatherin

Question 46

clatherin is a

Answer 46

coat protein

Question 47

how does the vesicle know where to go

Answer 47

Rab protein

Question 48

rab effector

Answer 48

moves vessicle to the plasma membrane

Question 49

SNAREs

Answer 49

mediate fusion

Question 50

v-snares

Answer 50

on the vesicle

Question 51

t-snares

Answer 51

on the target membrane