B2.1 Membranes and membrane transport HL

Question 1

voltage of resting potential

Answer 1

-70mV

Question 2

if action potential going through, what is the charge of the inside comparative to the outside?

Answer 2

inside more positive than outside

(originally outside more positive than inside)

Question 3

what moves to cause these changes?

Answer 3

sodium and potassium ions move

Question 4

what is threshold potential and what happens

Answer 4

sodium comes in at around -50mV

Question 5

at what voltage is an action impulse created at?

Answer 5

30mV

Question 6

when potassium leaves, what happens to voltage

Answer 6

voltage decreases

Question 7

why does only sodium pass through voltage gated sodium channel

Answer 7

how does sodium pass thru and not others → diameter of channel

channel is negatively charged/polar → can be attracted to sodium, things with negative charge is repelled

sodium is small enough to pass through

Question 8

why does only potassium pass through voltage gated potassium channel

Answer 8

potassium is bigger than sodium

when potassium goes through → potassium forms hydrogen bonds with oxygen on the surface of the ion channel

sodium doesn’t fit perfectly → still surrounded by water, cannot get rid of water → sodium ion cannot fit through

go through channel with water gate

need to break the water gate for sodium to go through

potassium can break water gate and form hydrogen bonds with oxygen

Question 9

the channels are () made for the size of ions

Answer 9

specifically

Question 10

what causes voltages across membranes

Answer 10

imbalance of positive and negative charges

Question 11

if voltage below -50mV, what happens to sodium and potassium channels

Answer 11

they remain closed

Question 11

if voltage above -50mV, what happens to sodium and potassium channels

Answer 11

sodium channels open, allowing Na+ ions to diffuse in ⇒ causes the voltage to rise more

Question 12

what happens to potassium channels when sodium channels open?

and why?

Answer 12

when sodium open, potassium close

when potassium open, sodium close

– due to differences in voltage

Question 13

if voltage reaches +40mV, what happens

Answer 13

potassium channels open, allowing K+ ions to diffuse out of the neuron

Question 14

differences in structure of lipid (triglyceride) of saturated & unsaturated fatty acids

Answer 14

saturated: solid in room temp, all fatty acids are straight

unsaturated: liquid in room temp, 2nd fatty acid is bent (bent = kink)

Question 15

effect of saturated or unsaturated lipid

what controls the ____

Answer 15

affect the fluidity of the membrane

The ratio of saturated and unsaturated fatty acids are controlled to determine the fluidity

Question 16

structure of membrane made of saturated fatty acids

Answer 16

fatty acids are longer

more perpendicular to membrane

membrane is thicker

Question 17

structure of membrane made of unsaturated fatty acids

Answer 17

more loosely packed due to kink

thinner and more fluidity

Question 18

structure of cholesterol

Answer 18

• most of cholesterol molecule → hydrophobic, attracted to hydrophobic hydrocarbon tails in centre of the membrane
• one end of molecule has a hydroxyl (-OH) group → hydrophilic, attracted to phosphate heads on the periphery
• cholesterol molecules are therefore positioned between phospholipids in the membrane, with the hydroxyl group usually facing outwards
• preferentially intercalates between saturated rather than unsaturated hydrocarbon chains

(-OH hydroxl group of cholesterol is polar (hydrophilic)

• rest of cholesterol is non-polar (hydrophobic)
• water is attracted to phosphate head; to move phospholipid away from each other → not too closely packed
• hydrophilic: attracted to phosphate head
• make a gap between the thingies (phospholipids??)
• cholesterol increases the fluidity in membrane)

Question 19

function of cholesterol

Answer 19

• stabilises membranes at higher temperatures, maintaining impermeability to hydrophilic particles (e.g. sodium ions, hydrogen ions)
• helps to ensure saturated fatty acid tails do not solidify at low temps → preventing a stiffening of the membrane

Answer 20

after sodium goes in, sodium increases to??

• once reach -50mV → all other sodium channels will open → a lot of sodium will go in
• voltage will increase → action potential → new impulse generated and passed on
• works with voltage gated sodium channel (potassium channel, sodium-potassium pump)
• nicotine → from smoking, can also bind onto receptors and opens it → addiction

Question 21

name of neurotransmitter related to nicotinic acetycholine receptor

Answer 21

acetycholine

Question 22

describe indirect active transport in proximal convoluted tubule

Answer 22

1) sodium-potassium pump will use ATP to actively transport Na+ ions out of the proximal convoluted tubule cells

2) low Na+ concentration is generated inside the cell

3) higher Na+ concentration in the lumen, this allows Na+ to diffuse into the cell using sodium-dependent glucose co-transporter

4) since glucose is co-transported into the cell, the cell has a higher glucose concentration

5) glucose will diffuse through the glucose channel proteins and back into the blood

6) this is known was indirect active transport

+as solutes (sodium, glucose) → water potential in cell decrease

lumen has a higher water potential

water move from lumen into the cell

as cell gains more water → water moves into the blood (lower water potential)+