Biol 373 - Unit 4b - Renal Function || 100% Accurate Answers.
How much fluid is filtered by the kidneys per day? correct answers 180L/day
How much fluid is excreted from the kidneys per day? correct answers 1.5L/day
What is the purpose of kidney filtration? correct answers - removes foreign/toxic substances in
addition to endogenous material
Why would you want to filter so much fluid if 99% of it is not excreted? correct answers One of
the major functions of the kidney is to selectively filter toxins from the blood. Selective filtration
would be too slow, whereas a high rate of filtration clears these substances quickly.
What happens when the default is set as "filtered --> excreted"? correct answers this makes it
easy to clear solutes without specific transport mechanisms.
Where is the largest proportion of fluid and solute reabsorbed? correct answers In the proximal
tubule.
What proportion of fluid and solute is reabsorbed in the proximal tubule? correct answers 70% of
fluid and solute.
Where does the 'fine-tuning' of water/salt balance occur? correct answers In the distal
tubule/collecting duct.
'Fine-tuning' of water/salt balance is under what type of control? correct answers Endocrine
control.
What does it mean to say that absorption in the proximal tubule is "iso-osmotic"? correct answers
- the fluid reabsorbed from here is iso-osmotic to blood plasma
,What is the osmolarity of fluid reabsorbed in the ascending loop of Henle? correct answers - it is
hypo-osmotic relative to plasma
What proportion of the original filtrate has been reabsorbed by the time passes through the
ascending loop of Henle? correct answers - 90%
What is the [solute] in the capsule filtrate in relation to the interstitial fluid (ICF)? correct
answers Filtrate in capsule has same [solute] as interstitial fluid.
What must be created by tubular cells in order to reclaim solute? correct answers - tubular cells
must create gradients (chemical/electrical) by active transport
How are gradients created? correct answers - Na+ is pumped out of tubule into the interstitium
- anions follow (since Na+ is positive)
- water follows due to osmotic draw
What is the consequence of water loss from the tubule? correct answers - remaining solutes in
tubular fluid is at higher concentrations (K+, Ca2+, urea)
- these solutes move into interstitium, if tubular epithelial cells are permeable to them
Is the apical side of epithelial cells in contact with the filtrate or the ICF? correct answers Apical
side is on filtrate side; basolateral side on ICF side.
Where do solutes that end up in the ICF go? correct answers They get picked up by a capillary
(i.e. enter the blood)
What are two ways that solutes can cross epithelial cells in the tubule? correct answers - para-
cellular pathway (through cell-cell junctions)
, - epithelial (trans-cellular) transport. i.e. by crossing the apical and basolateral membranes of
cells
What determines how easily K+, Ca2+ and urea move across the apical and basolateral domains?
correct answers Depends on which transporters are available (on both the apical and basolateral
domains).
Summarize the 4 steps of tubular reabsorption. correct answers 1. Na+ is reabsorbed by *active
transport*.
2. Electrochemical gradient drives anion reabsoprtion.
3. Water moves by *osmosis*, following the solute reabsorption. Concentrations of other solutes
increase as fluid volume in lumen decreases.
4. Permeable solutes reabsorbed by diffusion through membrane transporters or by paracellular
pathway.
What does the mechanism of epithelial (trans-celular) transport depends on? correct answers The
driving force.
If you have a *down* gradient, what would the mechanism of trans-cellular transport be? correct
answers - 'leak' channels or facilitated diffusion
What is the mechanism of trans-cellular transport if you are moving solutes against a gradient?
correct answers - primary or indirect active transport
What ion is involved in most trans-cellular transport? correct answers Na+; directly or indirectly
involved in most transport, both passive and active.
What does indirect active transport refer to? correct answers You are depending on the gradient
of another solute to move your solute of interest.
How much fluid is filtered by the kidneys per day? correct answers 180L/day
How much fluid is excreted from the kidneys per day? correct answers 1.5L/day
What is the purpose of kidney filtration? correct answers - removes foreign/toxic substances in
addition to endogenous material
Why would you want to filter so much fluid if 99% of it is not excreted? correct answers One of
the major functions of the kidney is to selectively filter toxins from the blood. Selective filtration
would be too slow, whereas a high rate of filtration clears these substances quickly.
What happens when the default is set as "filtered --> excreted"? correct answers this makes it
easy to clear solutes without specific transport mechanisms.
Where is the largest proportion of fluid and solute reabsorbed? correct answers In the proximal
tubule.
What proportion of fluid and solute is reabsorbed in the proximal tubule? correct answers 70% of
fluid and solute.
Where does the 'fine-tuning' of water/salt balance occur? correct answers In the distal
tubule/collecting duct.
'Fine-tuning' of water/salt balance is under what type of control? correct answers Endocrine
control.
What does it mean to say that absorption in the proximal tubule is "iso-osmotic"? correct answers
- the fluid reabsorbed from here is iso-osmotic to blood plasma
,What is the osmolarity of fluid reabsorbed in the ascending loop of Henle? correct answers - it is
hypo-osmotic relative to plasma
What proportion of the original filtrate has been reabsorbed by the time passes through the
ascending loop of Henle? correct answers - 90%
What is the [solute] in the capsule filtrate in relation to the interstitial fluid (ICF)? correct
answers Filtrate in capsule has same [solute] as interstitial fluid.
What must be created by tubular cells in order to reclaim solute? correct answers - tubular cells
must create gradients (chemical/electrical) by active transport
How are gradients created? correct answers - Na+ is pumped out of tubule into the interstitium
- anions follow (since Na+ is positive)
- water follows due to osmotic draw
What is the consequence of water loss from the tubule? correct answers - remaining solutes in
tubular fluid is at higher concentrations (K+, Ca2+, urea)
- these solutes move into interstitium, if tubular epithelial cells are permeable to them
Is the apical side of epithelial cells in contact with the filtrate or the ICF? correct answers Apical
side is on filtrate side; basolateral side on ICF side.
Where do solutes that end up in the ICF go? correct answers They get picked up by a capillary
(i.e. enter the blood)
What are two ways that solutes can cross epithelial cells in the tubule? correct answers - para-
cellular pathway (through cell-cell junctions)
, - epithelial (trans-cellular) transport. i.e. by crossing the apical and basolateral membranes of
cells
What determines how easily K+, Ca2+ and urea move across the apical and basolateral domains?
correct answers Depends on which transporters are available (on both the apical and basolateral
domains).
Summarize the 4 steps of tubular reabsorption. correct answers 1. Na+ is reabsorbed by *active
transport*.
2. Electrochemical gradient drives anion reabsoprtion.
3. Water moves by *osmosis*, following the solute reabsorption. Concentrations of other solutes
increase as fluid volume in lumen decreases.
4. Permeable solutes reabsorbed by diffusion through membrane transporters or by paracellular
pathway.
What does the mechanism of epithelial (trans-celular) transport depends on? correct answers The
driving force.
If you have a *down* gradient, what would the mechanism of trans-cellular transport be? correct
answers - 'leak' channels or facilitated diffusion
What is the mechanism of trans-cellular transport if you are moving solutes against a gradient?
correct answers - primary or indirect active transport
What ion is involved in most trans-cellular transport? correct answers Na+; directly or indirectly
involved in most transport, both passive and active.
What does indirect active transport refer to? correct answers You are depending on the gradient
of another solute to move your solute of interest.
