Chapter 4 Study Questions (Part 1) Flashcards
what are the two subcompartments of ECF?
- plasma
- ISF
what is a chemical driving force?
gradient
what is an electrical driving force?
voltage, like a battery
what is an electrochemical driving force?
both a gradient and voltage
what is the most abundant extracellular cation in the body?
Na+, sodium
what is the most abundant intracellular cation in the body?
K+, potassium
why is a resting membrane (+) on the outside and (-) on the inside ?
the inside is negative, and the membrane isn’t permeable, so it attracts positive charges.
which is the only ion that has a greater concentration outside the cell than inside the cell?
potassium
how does the concentration of one ion affect the chemical driving force of another ion?
not at all! independent of each other.
what is a membrane potential? what is another word for potential?
charge difference across the membrane.
voltage.
how does the ion concentration affect a membrane potential?
increase voltage with high (+) or (-) concentration
why is the membrane potential in a resting cell always referred to as a (-)Vm ?
it’s always negative on the inside.
Vm = membrane potential
does “high voltage” mean more or less negative?
more negative
what is equilibrium potential?
when the electrical force is equal to and opposite of an ion’s chemical force across a membrane
we understand “equilibrium” to mean…
no NET movement
describe how equilibrium potential works for Na+
lots of positive ions outside of the cell, and a negative charge inside.
positive will flow because of concentration gradient, but as (+) build up, they push against incoming (+) to stop them from coming in.
describe how equilibrium potential works for K+
lots of positive ions inside, and they flow out due to the concentration gradient. once enough of them leave, the remaining (+) will stay inside because of the electric attraction to the negatively charged inside of the cell
what three players are involved in maintaining a resting membrane potential?
Na+ leak channels
K+ leak channels
Sodium/potassium ATp-ase pump
why can’t the number of Na+ and K+ leak channels be the same ?
if lots of Na+ channels…
need Na/K ATP-ase to pump Na out
pumping Na out brings K in too
now you have too much K
what is the difference between passive and active diffusion?
P: requires no energy
A: requires energy
what is the difference between simple diffusion, facilitated diffusion, and active transport?
S: no membrane proteins
F: passive transport of molecules via transmembrane proteins
A: low to high, against gradient
Active Na+ transport drives what ?
symport of Na+ and glucose
symport: movement in the same direction across a membrane
if glucose is phosphorylated upon entry, how does it get out of the epithelial cell?
has to be dephosphorylated , then facilitated and simple diffusion into the bloodstream
what is the problem if intestinal epithelial cells brought glucose in from the intestine by facilitated diffusion?
if it flowed in while you were eating, it would flow out when you’re not via concentration gradients
what’s the difference between a transporter and a channel?
C: 2 openings
T: 1 opening that’s open/closed at a given time
describe the difference between primary and secondary active transport
P: gets energy from ATP
S: uses the energy that’s been stored in an ionic gradient across the membrane
although a glucose transporter is capable of transporting glucose in and out of a cell, why does it only transport in one direction? (2)
2 binding sites. when you bind 1, it changes the conformation of the other –> no binding.
it follows the principle of a gradient. when it’s closed, there is a higher concentration inside the cell.
