Exam 2 - Cell Membrane

Question 1

What is the cell membrane made of?

Answer 1

Phospholipid bilayer

Question 2

The heads of the phospholipid bilayer are _____.

Answer 2

hydrophilic

Question 3

The tails of the phospholipid bilayer are _____.

Answer 3

Hydrophobic

Question 4

What is the basic structure of a phospholipid?

Answer 4

Phosphate group on one end with a hydrocarbon tail coming off of it.

Question 5

What does the hydrocarbon tail of a phospholipid look like when there are no double bonds?

Answer 5

Saturated

Question 6

What does the hydrocarbon tail of a phospholipid look like when there is a cis double bond?

Answer 6

Unsaturated

Question 7

Are all cell membranes the same?

Answer 7

no

Question 8

What is the thickness of phospholipid bilayers that are unsaturated vs. saturated?

Answer 8

Unsaturated are thinner due to “bent” leg with cis-double bond

Question 9

T/F: It does not take energy for a cell membrane to maintain asymmetry.

Answer 9

FALSE – it does take energy to maintain asymmetry

Question 10

When does the cell membrane lose asymmetry?

Answer 10

When the cell is dead or dying

Question 11

What are the three main ways that molecules can cross a membrane?

Answer 11

1. Carrier protein
2. Channel protein
3. Passively w/o help

Question 12

What are the two main types of ion channels?

Answer 12

1. Always open (leak)

2. Gated

Question 13

What is an ion that uses a leak channel?

Answer 13

K+

Question 14

What are the two types of gated ion channels?

Answer 14

1. Voltage-gated

2. Ligand-gated

Question 15

What two ions use voltage-gated ion channels?

Answer 15

1. K+

2. Na+

Question 16

What ions use ligand-gated ion channels?

Answer 16

Na+

Question 17

What is membrane potential?

Answer 17

Electrical difference between the inside and outside of the cell

Question 18

What is the membrane potential inside vs. outside of the cell?

Answer 18

inside of cell is much more negative than the outside

Question 19

Why is the inside of the cell more negative than the outside?

Answer 19

Bc large NEGATIVELY charged proteins and other molecules cannot exit the cell

Question 20

What is the Goldman Equation used for?

Answer 20

Used to calculate the membrane potential

Question 21

What two things must be known in order to use the Goldman equation to calculate membrane potential?

Answer 21

1. Permeability of membrane to ions

2. Intracellular vs. extracellular concentration of ions

Question 22

What two things does the movement of ions depend on?

Answer 22

1. Electrochemical gradient

2. Permeability of membrane to ions

Question 23

What is the electrochemical gradient?

Answer 23

Electrical difference and ion’s concentration difference bt inside and outside of cell

Question 24

What does the permeability of membrane to ions depend upon?

Answer 24

Presence of open channels

Question 25

What is the concentration of Na+ inside vs. outside of the cell?

Answer 25

Lower on inside than outside

Question 26

What is the concentration of K+ inside vs. outside of the cell?

Answer 26

Higher on inside than outside

Question 27

What is the state of Na+ channels at rest?

Answer 27

Closed (low permeability)

Question 28

What is the state of K+ channels at rest?

Answer 28

Open (high permeability)

Question 29

Why doesn't more K+ enter the cell and make it less negative?

Answer 29

K+ wants to move down its concentration gradient (AKA OUT of the cell) so does not move into cell

Question 30

What is hyperkalemia?

Answer 30

Increase in EC K+

Question 31

How would electrochemical gradient for K+ be affected under hyperkalemia?

Answer 31

More driving force for K+ to move into the cell

Question 32

What would happen to the resting membrane potential under hyperkalemia?

Answer 32

It would decrease/become less negative/move close to 0.

Question 33

What would happen to the action potential under hyperkalemia?

Answer 33

Moves closer to threshold/more likely to happen

Question 34

What is hyponatremia?

Answer 34

Decrease in EC Na+

Question 35

How would the electrochemical gradient be affected under hyponatremia?

Answer 35

Less driving force for Na+ to move into cell

Question 36

What would happen to the resting membrane potential under hyponatremia?

Answer 36

Nothing because Na+ channels are closed

Question 37

What would happen to action potentials under hyponatremia?

Answer 37

They would be smaller

Question 38

If EC Na+ is decreased, what might happen to IC water balance?

Answer 38

Acute water intoxication