Exam 3 Lecture - Fluid Interaction Flashcards
What is the universal physiological solvent?
water
What is concentration of a solution?
percentage or parts solute per hundred of solvent
What is the difference between molarity and molality?
molarity is moles per L of solvent and molality is moles per kg of solvent
Explain the concept of electrochemical equivalence.
Electrochemical equivalence reflects that not all solutes have the same charge
- one equivalent has the same charge as one mole of H+
Why is concentration important?
because differences in concentration drive the interaction between fluids and are critical to how the kidney works
What are cell membranes composed of?
lipid bilayers
What molecules cannot cross the lipid bilayer?
charged particles and polar molecules
What molecules can cross the lipid bilayer?
small polar molecules
What is the function of the cell membrane?
act as a potent barrier and separate fluids that may have very different properties on either side of the membrane
What are the four mechanisms by which solutes interact at the lipid bilayer?
diffusion, facilitated diffusion, active transport, and secondary active transport
What is diffusion?
the movement of the solute in question down or with its concentration; from high to low
Is energy required for diffusion?
no
In order for diffusion to occur, the membrane must be what?
permeable to the solute in question
How long will diffusion occur?
until equilibrium is reached
In diffusion and facilitated diffusion, the bigger the gradient, the ______ it happens.
faster
In diffusion and facilitated diffusion, the ____ ________ the membrane, the ______ it happens.
more permeable, faster
What is facilitated diffusion?
the movement of a solute down or with its concentration from high to low concentration
Is energy required for facilitated diffusion?
no
Why is facilitated diffusion different than diffusion?
the mechanism is used if the membrane is not permeable so the diffusion is facilitated by transporters or pores in the membrane
How long does facilitated diffusion occur?
until equilibrium is reached
What is a renal example of diffusion?
paracellular reabsorption of Cl in the late proximal tubule
What is a renal example of facilitated diffusion?
Na, K, and Cl transport via NKCC2 in the macula densa to monitor glomerular filtration
What is the electrochemical gradient?
the net gradient of charge and concentration
What is active transport?
the movement of solute up or against its concentration gradient from low concentration to high concentration
Is energy required for active transport?
yes, energy provided by the hydrolysis of ATP
Aside from energy, what does active transport require?
a transport protein that moves the solute against its gradient; the transporter hydrolyses ATP
What is a renal example of active transport?
movement of Na at the basolateral membrane of proximal tubule (and other nephron sections) by NaK ATPase
What is secondary active transport?
the movement of solute up or against its concentration gradient from low to high concentration
How is secondary active transport different than active transport?
Energy is provided by the hydrolysis of ATP, however the transporter moving the solute does not hydrolyze ATP; instead it uses potential energy that has been generated by ATP-dependent processes elsewhere in the cell
What is osmosis?
the movement of water from an area where water concentration is high to an area where water concentration is low
In an area where the water concentration is high, what is the solute concentration like?
it is low
In an area where the water concentration is low, what is the solute concentration like?
it is high
For osmosis to occur, the membrane must ….
not be permeable to the solute in question
What is an effective osmole?
a solute that is unable to move across the membrane, creating the concentration difference between both sides
What is the difference between osmolarity and osmolality?
osmolarity is the concentration of osmotically active atoms per L of solvent
Osmolality is the concentration of osmotically active atoms per Kg of solvent
How many osmotically active ions would NaCl have?
2 - one for Na, one for Cl
Is the osmolarity of a highly concentrated solution low or high?
high
What is tonicity?
the concentration of effective osmoles in a fluid
What is a hypertonic solution?
a solution with a higher effective osmolarity than another
If a cell with low osmolarity is placed into a hypertonic solution, what happens?
the water will move from inside the cell to the solution causing the cell to shrink
What is a hypotonic solution?
a solution with a lower effective osmolarity than another
If a cell with high osmolarity is placed into a hypotonic solution, what happens?
the water will move from the solution into the cell causing it to swell
What is an isotonic solution?
a solution with the same effective osmolarity as another; there is no osmosis generating pressure
What is a renal example of secondary active transport?
the movement of glucose and amino acids at the luminal membrane of the proximal tubule
How is the energy of the movement of glucose and amino acids at the luminal membrane of the proximal tubule provided?
the downhill movement of Na into the cell via the same transporter; the sodium is moving down a gradient that was establisged by NaKATPase which burns the ATP
