Transport

Question 1

Na+/K+ ATPase

Answer 1

-plasma membrane transporter
-3 Na+ out of cytosol into extracellular fluids
-2 K+ in to cytosol (intracellular fluid)
-hydrolysis of 1 ATP –> ADP + Pi = 30% of ATP use in cells
-Na+/K+ gradient: prevent cell swelling due to osmosis, Na+ gradient can be used to transport other substances across membrane (co- or counter transport)

-active transport; pump against gradient from low to high concentration
-Na+ high [ ] outside and pump out more
-K+ high [ ] inside and pump in more

Question 2

concentration intracellular vs extracellular of:
Na+, K+, Cl-

Answer 2

Na+ high extracellular
K+ high intracellular
Cl- high extracellular

Question 3

passive transport; what is able to do passive transport?

Answer 3

-high to low [ ]
-diffuse
-use channels or transporters unless molecule is small and hydrophobic (i.e. CO2 or O2)

-includes facilitated transport

Question 4

active transport; where is energy gotten?

Answer 4

energy needed
-energy from ATP hydrolysis
-energy from gradient of other molecules
–> requires internal membrane protein

-includes co-transport and counter- transport

Question 5

active transport process and example

Answer 5

a protein moves a substance across a membrane against a concentration gradient

i.e. Na+/ K+ ATPase

Question 6

passive transport process and example

Answer 6

a protein forms a channel that allows a substance across the membrane, along its concentration gradient

i.e. aquaporins (for H2O)

Question 7

facilitated transport process and example

Answer 7

-passive
-a protein carrier binds to a substance and transports it across a membrane, allowing it to follow its concentration gradient (move large molecules)

i.e. glucose transporter GLUT

Question 8

co-transport process and example

Answer 8

-active (use energy of something else)
-the transport of 2 substance (X and Y) are coupled using the same protein. the concentration gradient of X favours movement into the cell- Y is “pulled” along, even if the gradient for Y does not favour cell entry

i.e. sodium-glucose co-transporter (SGLT-1 and -2)

Question 9

counter-transport process and example

Answer 9

-active (use energy of something else)
-X and Y move in opposite directions across the cell membrane- the gradient of one of the molecules supplies the energy to drive the transport

i.e. Cl-/HCO3 counter-transporter

Question 10

what prevents cell swelling

Answer 10

Na+/K+ pump

when ATP levels fall to 10% of normal levels bc then ATP can’t push Na+ out of cell and Na+ attracts H2O