Lecture 4 Flashcards
8/30
What is osmotic pressure?
The physical pressure, measured in mmHg, required to prevent osmosis from occurring through a semipermeable membrane.
What is osmotic pressure generated by?
The movement of water
What do you need in order to have osmosis?
A solution/H2O; a soluble solute; a semipermeable membrane
Can osmosis occur with an insoluble solute?
No. Has to be charged and able to dissolve in water
A semipermeable membrane _______ the movements of solutes.
Restricts
What happens when you add solute to 1 side of a semipermeable membrane?
The osmolarity of that side will increase and the water concentration will decrease. Water will move across the semipermeable membrane to equalize the water concentration on both sides
H2O want to flow ________ its concentration gradient
Down
What is Osmolality?
How much of a quantity of stuff we have dissolved in 1kg of H2O
Normally used in calculating osmotic pressure
Osmolality = 1 mOsm / 1 kg H20
What is Osmolarity?
How much of a quantity of stuff we have dissolved in 1L of solution.
Osmolarity = 1 mOsm / 1L of solution
What are the differences between Osmolality and Osmolarity?
WE WILL NOT BE USING OSMOLALITY IN CLASS. WE WILL BE USING OSMOLARITY!!!!
Osmolality is in 1kg of water and osmolarity is in 1L of solution (solution can be blood)
There’s about a 1% difference between them
What is the formula for Osmotic Pressure?
Osmotic pressure = (19.3 mmHg / 1 mOsm) x ( Osmolarity in mOsm / 1L of solution)
What is total osmotic pressure?
All the pressure that can be generated from fluid shifts d/t substances in the blood.
How much pressure does 1 mOsm of a solute create?
19.3 mmHg
Can you have osmosis with an impermeable membrane?
No.
1 mOsm of a solute will move _____________ by 19.3 mm
A column of Hg
What is most of the energy in a cell used for? What percentage of the energy of the cell is being used by this?
Cycling the Na+/K+ ATPase pump
60-70%
What kind of transport pump is the Na+/K+ ATPase pump? Why?
It is a Primary (or 1st degree) active transport; this is because the pump uses ATP directly.
Briefly describe the Na+/K+ ATPase pump.
Located within the cell wall
Goes against the electrochemical gradient
Uses ATP directly
Takes a phosphate off ATP to make ADP + Pi
Pumps 2 K+ into the cell
Pumps 3 Na+ out of the cell
What are the effects of the Na+/K+ ATPase pump on the cell?
Pump keeps osmolarity of cell in a steady state; Works as a dialyzing pump as well because the water will leave the cell because the reduced Na+; Contributes to making the cell more negative because the cell loses 1 positive charge per cycle
Where does the Na+ that the Na+/K+ ATPase pump come from? Where does the water come from?
Na+ enters into the cell via secondary active transport (NCX transporter). H2O enters into the cell via AQP and electrolyte channels.
What happens when the Na+/K+ ATPase pump isn’t working?
The Na+ in the ICF will increase and the K+ in the ECF will increase. The water will stay inside the cell and cause cellular edema which is extremely hard to fix; Increased K+ in the ECF will increase cardiac events. You have to fix the ATP inside the cell to fix the problem.
What is V(max)?
Max speed at which conformation change can occur; once at Vmax, you can’t move faster.
What does the speed of facilitated diffusion depend on?
The concentration gradient
The amount of carrier proteins available
The amount of time it takes the protein to make the conformational change
What happens during facilitated diffusion?
A molecule binds to a carrier protein; The protein makes a conformational change; the molecule is released on the opposite side. This process can go both ways; net movement is always determined by the concentration gradient.
Describe the GLUT-4 transporter
Helps facilitate the movement of sugar; Insulin-dependent; Higher number in muscle and fat cells
Describe the GLUT-1 transporter
Helps facilitates the movement of sugar; Non-insulin dependent; Used in RBC and the BBB; Ubiquitous
What does ubiquitous mean?
It means being present everywhere; to be found everywhere.
Does simple diffusion have a V(max)? Why?
No. Simple diffusion increases linearly with an increase in the concentration gradient; simple diffusion has no conformation limiting factors that would limit the rate of diffusion.
How does concentration affect the rate of diffusion?
The bigger the difference the faster the rate
How does membrane solubility affect the rate of diffusion?
The more LIPID soluble = the easier it is to get through the cell wall
How does the size of the particle affect the rate of diffusion?
The smaller the particle the higher the rate of diffusion
How does size of the pores affect the rate of diffusion?
The bigger the pores the higher the rate of diffusion
How does the number of pores affect the rate of diffusion?
The more pores you have, the higher the rate of diffusion.
How does kinetic movement (heat) affect the rate of diffusion?
Increased movement = increased rate
How does physical pressure affect the rate of diffusion?
increased pressure = increased rate
How does electrical charge affect the rate of diffusion?
Increased opposing charge = increased rate
At rest, excitable cells are ___________ on the inside
electronegative
What unit is Resting membrane potential V(rm) calculated in?
millivolts
mV
What happens when a resting cells becomes active?
They become more positively charged for a short amount of time.
What pump contributes to keeping the cell negative?
The Na+/K+ ATPase pump; you lose 1 positive charge each cycle.
A _________ cell is usually capable of turning back on.
Resting
T/F: Most cells don’t have membrane potential
False. Almost all cells have membrane potential
What is the charge of most proteins?
Negative
Proteins are an important _________ buffer
intracellular
What is the relationship between proteins and cellular charge?
Proteins are mostly negatively charged and they usually hang out in the cell wall sticking out INTO the cell. Therefore the negative charge of proteins contributes to the overall negative charge of the cell.
What do most proteins that stick out on the outside of the cell do? Give me an example
They are usually a part of cell transduction/communication.
Ex) GCPR
What is the Nernst Potential formula?
“Equilibrium Potential”
EMF = +/- 61 x log(Ci / Co)
Formula that tells us what the charge would be if a cell was only permeable to that specific ion. Measured in mV
What does EMF mean?
Electromagnetic force
What ions are cells permeable to at rest?
Na+ and K+
The cell is 10x more permeable to K+ than Na+
What is the resting charge of a cell most dependent on?
K+ because it is 10x more permeable than Na+
What is the EMF of Na+ at rest?
61 mV
What is the EMF of K+ at rest?
-90.1 mV
What is Nernst Potential?
The voltage that will prevent ions from diffusing across the membrane, down their concentration gradients.
What is the overall membrane potential of a cell at rest?
About -80 mV;
10x more permeable to K+ than Na+ so answer is closer to K+
What happens to the permeability of the cell when turned on?
May become more permeable to Na+ and may become permeable to other ions.
How do you know what sign to use in front of the 61 in the Nernst formula?
It is ion dependent
If it is a cation (+) use negative
If it is an anion (-) use positive
What is the Goldman Equation?
Combination of individual equilibriums of all ions that the cell is permeable to, to find the overall membrane potential of a cell
Will not use the equation.
EMF = -61 x log(C(Nai)+P(Na)…. / C(Nao)+P(Na)…..)
