Chapter 4 Study Questions (Part 1)

Question 1

what are the two subcompartments of ECF?

Answer 1

1. plasma
2. ISF

Question 2

what is a chemical driving force?

Answer 2

gradient

Question 3

what is an electrical driving force?

Answer 3

voltage, like a battery

Question 4

what is an electrochemical driving force?

Answer 4

both a gradient and voltage

Question 5

what is the most abundant extracellular cation in the body?

Answer 5

Na+, sodium

Question 6

what is the most abundant intracellular cation in the body?

Answer 6

K+, potassium

Question 7

why is a resting membrane (+) on the outside and (-) on the inside ?

Answer 7

the inside is negative, and the membrane isn’t permeable, so it attracts positive charges.

Question 8

which is the only ion that has a greater concentration outside the cell than inside the cell?

Answer 8

potassium

Question 9

how does the concentration of one ion affect the chemical driving force of another ion?

Answer 9

not at all! independent of each other.

Question 10

what is a membrane potential? what is another word for potential?

Answer 10

charge difference across the membrane.

voltage.

Question 11

how does the ion concentration affect a membrane potential?

Answer 11

increase voltage with high (+) or (-) concentration

Question 12

why is the membrane potential in a resting cell always referred to as a (-)Vm ?

Answer 12

it’s always negative on the inside.

Vm = membrane potential

Question 13

does “high voltage” mean more or less negative?

Answer 13

more negative

Question 14

what is equilibrium potential?

Answer 14

when the electrical force is equal to and opposite of an ion’s chemical force across a membrane

Question 15

we understand “equilibrium” to mean…

Answer 15

no NET movement

Question 16

describe how equilibrium potential works for Na+

Answer 16

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.

Question 17

describe how equilibrium potential works for K+

Answer 17

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

Question 18

what three players are involved in maintaining a resting membrane potential?

Answer 18

Na+ leak channels

K+ leak channels

Sodium/potassium ATp-ase pump

Question 19

why can’t the number of Na+ and K+ leak channels be the same ?

Answer 19

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

Question 20

what is the difference between passive and active diffusion?

Answer 20

P: requires no energy

A: requires energy

Question 21

what is the difference between simple diffusion, facilitated diffusion, and active transport?

Answer 21

S: no membrane proteins

F: passive transport of molecules via transmembrane proteins

A: low to high, against gradient

Question 22

Active Na+ transport drives what ?

Answer 22

symport of Na+ and glucose

symport: movement in the same direction across a membrane

Question 23

if glucose is phosphorylated upon entry, how does it get out of the epithelial cell?

Answer 23

has to be dephosphorylated , then facilitated and simple diffusion into the bloodstream

Question 24

what is the problem if intestinal epithelial cells brought glucose in from the intestine by facilitated diffusion?

Answer 24

if it flowed in while you were eating, it would flow out when you’re not via concentration gradients

Question 25

what’s the difference between a transporter and a channel?

Answer 25

C: 2 openings

T: 1 opening that’s open/closed at a given time

Question 26

describe the difference between primary and secondary active transport

Answer 26

P: gets energy from ATP

S: uses the energy that’s been stored in an ionic gradient across the membrane

Question 27

although a glucose transporter is capable of transporting glucose in and out of a cell, why does it only transport in one direction? (2)

Answer 27

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.