Exam 2 - Cell Membrane Flashcards
What is the cell membrane made of?
Phospholipid bilayer
The heads of the phospholipid bilayer are _____.
hydrophilic
The tails of the phospholipid bilayer are _____.
Hydrophobic
What is the basic structure of a phospholipid?
Phosphate group on one end with a hydrocarbon tail coming off of it.
What does the hydrocarbon tail of a phospholipid look like when there are no double bonds?
Saturated
What does the hydrocarbon tail of a phospholipid look like when there is a cis double bond?
Unsaturated
Are all cell membranes the same?
no
What is the thickness of phospholipid bilayers that are unsaturated vs. saturated?
Unsaturated are thinner due to “bent” leg with cis-double bond
T/F: It does not take energy for a cell membrane to maintain asymmetry.
FALSE – it does take energy to maintain asymmetry
When does the cell membrane lose asymmetry?
When the cell is dead or dying
What are the three main ways that molecules can cross a membrane?
- Carrier protein
- Channel protein
- Passively w/o help
What are the two main types of ion channels?
- Always open (leak)
2. Gated
What is an ion that uses a leak channel?
K+
What are the two types of gated ion channels?
- Voltage-gated
2. Ligand-gated
What two ions use voltage-gated ion channels?
- K+
2. Na+
What ions use ligand-gated ion channels?
Na+
What is membrane potential?
Electrical difference between the inside and outside of the cell
What is the membrane potential inside vs. outside of the cell?
inside of cell is much more negative than the outside
Why is the inside of the cell more negative than the outside?
Bc large NEGATIVELY charged proteins and other molecules cannot exit the cell
What is the Goldman Equation used for?
Used to calculate the membrane potential
What two things must be known in order to use the Goldman equation to calculate membrane potential?
- Permeability of membrane to ions
2. Intracellular vs. extracellular concentration of ions
What two things does the movement of ions depend on?
- Electrochemical gradient
2. Permeability of membrane to ions
What is the electrochemical gradient?
Electrical difference and ion’s concentration difference bt inside and outside of cell
What does the permeability of membrane to ions depend upon?
Presence of open channels
What is the concentration of Na+ inside vs. outside of the cell?
Lower on inside than outside
What is the concentration of K+ inside vs. outside of the cell?
Higher on inside than outside
What is the state of Na+ channels at rest?
Closed (low permeability)
What is the state of K+ channels at rest?
Open (high permeability)
Why doesn’t more K+ enter the cell and make it less negative?
K+ wants to move down its concentration gradient (AKA OUT of the cell) so does not move into cell
What is hyperkalemia?
Increase in EC K+
How would electrochemical gradient for K+ be affected under hyperkalemia?
More driving force for K+ to move into the cell
What would happen to the resting membrane potential under hyperkalemia?
It would decrease/become less negative/move close to 0.
What would happen to the action potential under hyperkalemia?
Moves closer to threshold/more likely to happen
What is hyponatremia?
Decrease in EC Na+
How would the electrochemical gradient be affected under hyponatremia?
Less driving force for Na+ to move into cell
What would happen to the resting membrane potential under hyponatremia?
Nothing because Na+ channels are closed
What would happen to action potentials under hyponatremia?
They would be smaller
If EC Na+ is decreased, what might happen to IC water balance?
Acute water intoxication
