Membrane Transport Flashcards
Define Isotonic? (Healthy size cell)
Solute concentration(osmotic pressure) is the same inside and outside the cell.
Define Hypotonic.(Very swollen cell)
Solute concentration (osmotic pressure) is greater inside the cell than outside the cell.
Define hypertonic.(“Dehydrated” looking cell)
Solute concentration(osmotic pressure) is lower in the cell than outside the cell.
What energy drives diffusion? (No barriers)
Diffusion occurs due to the inherent, kinetic energy of molecules and the potential energy stored in a concentration gradient.
Is osmosis diffusion of water? (P Bio 375)
NO!
Define osmosis.
The flow of water across a water permeable membrane toward a region of higher solute concentration.
What differs diffusion from osmosis?
Diffusion depends upon a concentration gradient. Osmosis depends on osmotic pressure; the number of solute particles. (Neither their size, charge state, nor hydrophilicity have effect of the osmotic pressure of the system.)
Define Aquaporins.
Transmembrane proteins that form water channels.
Define osmolarity and osmolality.
Osmolarity: Number of particles of solute per liter of water.
Osmolality: Number of particles of solute per kilogram of water.
Osmotic flow of water is through 1.__________. Water flows 2.____ an osmotic gradient.
- Aquaporins
- Up
Define osmotic pressure.
A colligative property: it depends on the number of particles of solute, but not the nature of the particles.
The pressure that must be applied to oppose osmosis.
Why is osmotic pressure important for hydrostatic pressure?
Osmotic pressure counteracts hydrostatic pressure to prevent fluid from leaving the capillaries.
Define colloid osmotic pressure (π)
Is the osmotic pressure due to the plasma proteins within the capillary, pulls fluid into the capillary.
Define hydrostatic pressure. (Pʜ)
Pressure that forces fluid out of the capillary.
Which pressure has more strength generally? Hydrostatic pressure (Pʜ) or Colloid osmotic pressure (pi)
Hydrostatic pressure.
This means about 3L of fluid per day leaves the capillaries.
This is returned to the circulatory system as lymph.
Define tonicity.
The relative level of non-penetrating solutes in a fluid in which cells are being bathed.(in Lec)
Or
The capability of a solution to modify the volume of cells by altering their water content .(Google)
The ability of extracellular solution to make water move into or out of a cell by osmosis . (Google)
Define channel. What are common types?
A water filled hole, transmembrane protein(s). Aquaporins, and ion channels, both gated and ungated,
What are the two main properties of ion channels. Name all ions important for this class(4). Name the types of gated channels(5).
- Selectivity: What type of ion does through.
Ex. Na+, K+, Ca++, Cl- - Gating: What opens or closes the channel.
Ex. Ungated channel = Leak channel, voltage gated-channel, ligand gated = chemically gated, mechanically gated channel, temperature gated channel.
What’s the difference between passive and active transport.
Active requires ATP (directly or indirectly).
Passive requires only a gradient (being gated doesn’t mean it needs ATP!)
Define what a Carrier Protein is.
Carrier proteins have two confirmations that expose the binding site to either the extracellular fluid or the intracellular fluid. They are NOT a continuous pore like a channel. (Also called transporter/symporter)
What is the GLUT protein responsible for?
It is a glucose transporter(carrier protein!) that is responsible for the facilitated diffusion of glucose. (Uses facilitated diffusion)
Define facilitated diffusion.
A passive process that depends only on the concentration gradient. Requires aid of membrane protein to carry out the diffusion. (Ex. H2O & Aquaporins, Glucose and GLUT protein.)
Define primary active transport. (Carrier protein still)
Utilizing ATP energy in order to change the conformation of the carrier protein.
Ex. Na+/K+-ATPase!
What are 3 common examples of Primary active transport ATP-ases?
- Na+/K+-ATPase (sodium potassium pump): uses ATP hydrolysis to pump 3 Na+ ions out of the cell and 2 K+ ions into the cell for each round of transport.
- Ca++-ATPase: pumps Ca++ out of cytosol.
- H+/K+-ATPase: proton pump involved in acid secretion in the stomach.
Notable concentration gradients of ions in ICF vs ECF. Note things about Na+, K+, and Cl-. Why are these gradients notable?(2 reasons)
Na+ generally has a higher concentration outside of the cell.
K+ generally has a lower concentration outside the cell.
Cl- generally has a higher concentration outside of the cell.
The gradients are key for 1. Membrane potential and 2. Secondary active transport.
Define secondary active transport and a common example. What are the two types of secondary active transport?
The use of energy from one gradient to power transport of another gradient (often unfavorable/going against a gradient).
Ex. Na+-glucose cotransporter. SGLT protein
Two types: 1. Transport molecules in the same direction (cotransporter, or symporter). 2. Transport molecules in the opposite direction (countertransporter, or exchanger.)
What is required for the SGLT protien (sodium-glucose cotransporter) to work? How is it used?
Requires both Na+ and glucose to be binded to the carrier protien for transport to occur.
This protien is involved in the key first step in the absorption of glucose from the digestive tract.
Define saturation of carrier proteins. Can channels be saturated?
The transport rate reaches a maximum at high concentrations when all carrier binding sites are occupied.
No channels can not.
Define competitive inhibition of carrier proteins. Can channels have competitive inhibition?
A molecule that competes with the transported substance for the binding site will lower the rate of transport.
No channels do not have competitive inhibition.
Define competitive inhibition of carrier proteins. Can channels have competitive inhibition?
A molecule that competes with the transported substance for the binding site will lower the rate of transport.
No channels do not have competitive inhibition.
Optional: what is SGLT2?
Sodium-glucose cotransporter in the kidney tubules.
Define Epithelia
Tissues, that form a barrier between the external environment and the internal environment of the body.
What are the two sides(membranes) of a epithelium? What do they face respectively? What separates them?
The Apical membrane/side faces the lumen. (Kinda spikey)
The Basolateral membrane/side faces the underlying tissue. (Smoother)
These membranes are linked by tight junctions between adjacent cells.
Define what a lumen is.
The space within the tubes, tracts, cavities, and cells of the body. Air, blood, fluids, food, and other substances move through the lumen.
Why is it beneficial that the epithelium has two separate membrane layers?
Different transport proteins are localized on the apical vs basolateral surfaces of epithelial cells to enable transport in one direction across both membranes of the epithelium. Transport can be more selective in direction.
Define secretion of the epithelium.
Transport from ECF to lumen.
Define absorption in the epithelium.
Transport from lumen to ECF(body).
Fluid secretion happens why? (Secretion of Epithelium)
Happens because of osmosis, as ions(solutes) move into lumen, creates a higher degree of osmolairty inside the lumen and water follows by osmosis.
Ions move in between the membranes through(only ECF ->basolateral membrane):
1. Na+/K+-ATPase
2. Cotransporter that moves Na+,K+,and Cl- (symporter)
Ions move from between membrane to lumen through (apical membrane -> Lumen):
1. CFTR (a chloride channel)
