Lecture 7- transport across membranes

the K+ ion channel is:

voltage-gated

he Na+/Ca++ exchanger (NCX) works by what to
control Ca++ levels

antiport

removes calcium from the what by using energy stored by the Na+ gradient (one Ca++ “out” for 3 Na+ in) secondary active
transport (coupled)

cytosol

the Na+/Ca++ exchanger (NCX) works by antiport to
control Ca++ levels: has a low affinity for Ca++ but what
capacity (ie, fast at high concentrations

high

Ca++ is an important messenger within the cell and can be released to send what

signals

Calcium levels are low in the cytosol because it is pumped out into the what and the membrane is highly impermeable to the ion

extracellular space

Calcium channels can be transiently opened by
action potential or what itself

calcium

Calcium binds to what, which
can initiate downstream signals (like heart beats)

calcium-binding proteins

ouabain and digoxin bind to the Na+/K+ pump (not shown) and
inhibit it, resulting in what intracellular sodium.
this reduces the NCX function and yields what intracellular calcium, making heartbeats stronger and more frequent

higher

what transporters are highly regulated

active

Ca2+ATPase hydrolyses # ATP for each Ca2+ ion transported

1

Ca2+ ATPase can export Ca++ (on plasma membrane) or pump it into the ER (or sarcoplasmic reticulum) for what when needed

storage

with respect to the Na+/K+ ATPase pump, which of the following is TRUE?

ions move more slowly through a pump than a channel because because only a few ions move per ATP hydrolysis instead of continuously

with respect to the Na+/K+ ATPase pump, which of the following is FALSE?

it must have a higher binding affinity for K+ outside of the cell and a lower binding affinity for K+ inside the cell

the difference in charge across the membrane is the what

membrane potential

membrane potential is largely due to Na+ K+ ATPase and some flow of K+ back via what channels

leak

# mV is a standard membrane potential for a
(resting) mammalian neuron, but varies according
to cell type/organism

-70

the myelin sheath acts as a what

insulator

the disease Multiple sclerosis (MS) is caused by what of the myelin sheath

disruption

an action potential is the what change in charge across the membrane

rapid

action potential occurs in what cells, ie, nerves, muscle, beta pancreatic cells, endocrine cells, some plant cells

excitable

takes place via the rapid what of voltage gated ion channels (then what

opening, closing

action potential stimulus does what to the membrane

depolarizes

Na+ channel opens, Na+ influx →

#mV (close to equilibrium)

40

Change in potential opens K+ gates
→ #mV (repolarization)

-80

action potential: Na+ stimulus K+ slowly leaks out

what mV

-70

action potential: Na+ depolarization (past threshold)

what mV

-50

action potential: Na+ voltage gated channels open, Na+ goes in

what mV

40

action potential: K+ voltage gated channels open (Na+ channels close) (K+ out)

what mV

30

action potential: K+ channels close (although leak channels are open)

what mV

-80

changes in membrane potential regulate the which channel

K+

the voltage required to open/close the channel is what type dependent

cell/protein

depolarization of membrane

Rest

spontaneous

Open/Inactivated

K+ Leak channels are or are not voltage gated

are not

nerves “do what” to muscles at the neuromuscular junction

talk

how nerves send signals in your body

synaptic transmission