Transport Mechanisms Flashcards
What determines the specific function of the different parts of the nephron?
Based on the cells that make up that portion of the tubule
What is urine?
The products that they body needs to rid it of and that the body no longer needs
What % fluid does the proximal tubule filter?
65% is filtered and reabsorbed
-Na, K, Cl, H2O, AA Glucose
What % fluid does the loop of Henle filter?
20% is filtered and reabsorbed
What does each side of the loop of Henle filter?
Descending Loop –> H2O and minimal Na
Ascending Loop –> Na, K, Cl
What %R fluid does the Distal tubule and Collecting duct filter?
14% is filtered and reabsorbed
- Distal: Na, K, Cl, Ca
- Collecting: Na, H2O *fine tunes these depending on hormone balance
What is the tubule made up of?
Single layer of epithelial cells linked by junctions
What is the apical/luminal membrane?
The membrane of a tubule epithelial cell facing the inside of the tubule
What is the basolateral membrane?
The membrane of a tubule epithelial cell facing the outside of the tubule
What are the 2 forms of tubule transport?
- Reabsorption
2. Secretion
What are the 2 kinds of reabsorption?
- Paracellular
2. Transcellular
What is paracellular transport?
When ions/substances within the tubule move in-between tubule cells
-1 step process
What is Transcellular transport?
When ions/substances within the tubule move through tubule cells
-2 step process passing through luminal and basolateral membrane
What is secretion in terms of tubule transport?
When substances from the capillaries enters the tubule usually always transcellular
What are the 3 transport mechanisms?
- Channels
- Transporters
- Primary active transporters
Describe the transport mechanism for channels?
- Simple diffusion mechanism
- Basic ion channel
- Protein lined pores that allow specific substances through
- Driven by [] gradient or electrochemical gradient
What are the 3 types of transporters?
- Uniporters
- Symporters
- Antiporters
What is a uniporter?
Permits the movement of a single molecule through the membrane via protein configuration
- protein carrier that binds the molecule
- can become saturated
What is a symporter?
Permits the movement of 2 molecules in the same direction across a membrane
-at least 1 molecule must move down its [] gradient to move both molecules
What is secondary active transport?
When one molecules energy derived [] gradient is used to do work without ATP
What are antiporters?
Permits the movement of 2 molecules in opposite directions across a membrane.
-molecule must move down [] gradient for the other molecule to move
What is a Primary Active Transporter
Requires ATP to move molecules against their [] gradient
-protein carrier embedded in the membrane
What are the 3 ways in which transporters are regulated in the kidney?
- Regulation at the level of Gene Expression
- Regulation at the level of Cellular Location
- Regulation at the level of Activity
What does it mean when you have a regulated transporter?
A specific transporter/channel is changed in its function in response to a hormone
What does it mean when you have a non-regulated transporter?
Transport occurs at a constant rate
What is Regulation at the level of Gene Expression?
When you take the DNA sequence and make more transporters/channels
-can express the channel/transporter more or less depending on the hormone level
What is Regulation at the level of Cellular Location?
Protein carriers can only work when they are in the membrane. If they are floating around they are not able to perform their function
What is Regulation at the level of Activity?
When it is possible to make the transporter/channel better, faster or slower depending on hormone levels
