Module 1 Lecture 7: Tonicity + Osmolarity & Unassisted and Assisted Membrane Transport Flashcards
What is tonicity?
Effect that a solution has on the volume of the cell
What is the tonicity of the solution determined by?
Non-penetrating solutes in the solution
What does tonicity do to the volume of a cell?
Either make the volume stay the same, increase or decrease
What do the penetrating solutes do in the solution (Tonicity)
Penetrating solutes exchange equally in the ECF and ICF
What is isotonic?
When the cell volume stays the same
What is hypotonic?
Solution that makes the volume swell in the cell
What is hypertonic?
Solution that makes the volume decrease in the cell
If we had 300mosm of non penetrating solutes in a beaker and we put a RBC with 300mosm of non-penetrating solute in the intracellular fluid in the beaker what would the tonicity turn out to be?
Isotonic because the non-penetrating solute concentration is equivalent meaning none of them have more water than the other
What is Osmolarity?
Measure of solute concentration per unit of solvent (you count both penetrating and non-penetrating solute concentrations)
How is osmolarity different from tonicity?
Take into account all solute concentration (you count both penetrating and non-penetrating solute concentrations)
What affects the volume of a cell? Tonicity or Osmolarity?
Tonicity (only concentrations of non-penetrating solutes)
What is iso-osmotic?
Osmolarity of a solution is equal to the osmolarity of a cell
What is hypo-osmotic?
If the osmolarity of the solution is lower than the osmolarity of the cell
What is hyper-osmotic?
Osmolarity of the solution is higher than the osmolarity of the cell
What is molarity?
Ratio of solvents moles to the entire solution (i.e. 200mmol of NaCl dropped in solution still means 200mmol of that concentration)
How do ion forming compound affect osmolarity? Explain using NaCl
With NaCl these compounds can dissolve in solution (like water) and form ions which makes the osmolarity twice the amount because each ion affects the movement of water (osmotic pressure) due to them both being non-penetrating
Why is osmolarity>molarity
Molarity takes into account the concentration of that solute (compound) as a whole in terms of the solution it is in.
Osmolarity looks at the total amount of solutes present (individual ionic ions)
Can large, poorly lipid soluble molecules passively move through the membrane?
No; requires assisted transport
What are the two mechanisms in active transport?
Carrier-mediated transport & Vesicular transport
What can carrier proteins do in the membrane when it takes a molecule in or kicks a molecule out?
It can change its shape so that the binding sites face the ICF or ECF
What are the three characteristics of carrier mediated transport proteins?
Specificity, Saturation and Competition
What does specificity mean in carrier mediated transport?
Binding sites will only expose itself to specific molecules (Glut transporter only takes glucose)
What does saturation mean in carrier mediated transport?
A limited number of carrier binding sites
What does competition mean in carrier mediated transport?
Closely related compounds compete to get access
How does saturation work?
If we have 100 glucose transporters but have 1000 molecules of glucose only 100 of them can go at a time; limited by the number of carrier binding sites
What are the two forms of carrier-mediated transport?
Active and passive
What is facilitated diffusion?
Uses carrier molecules to assist the transfer of substances across the membrane from high concentration to low concentration
Does a carrier-mediated transport need to use energy?
Not necessarily; if it’s something moving from high to low concentration then no need even if it’s a substance that requires the carrier-mediated transport to cross the membrane but in other cases it can use energy
Type of diffusion where it’s passive but requires a carrier is?
Facilitated diffusion
Passive diffusion is defined as?
Transfer of substance from high concentration to low concentration without assistance of a carrier
What is facilitated diffusion rate limited by?
Saturation and Ficks Law
Explain how facilitated diffusion would occur with glucose?
1) High concentration of glucose outside the cell can’t pass through the membrane itself so it goes to a carrier-mediated transport protein specific to glucose
2) Carrier in resting state faces the outside of the cell with it’s binding site open to glucose.
3) Once glucose binds to it the carrier protein shifts (confirmational change) from outside the cell
4) Glucose molecule is automatically released because there’s a lower concentration of glucose in the area it’s headed to
5) Once the glucose is gone and the binding site is empty; the carrier flips back to original position to repeat the process
How is the rate of diffusion in simple diffusion differ from carrier-mediated transport?
Simple diffusion goes with fick’s law => greater concentration means faster the rate of diffusion
In carrier-mediated, there are things limiting the rate of diffusion, specifically saturation which makes the rate of diffusion, plateau if there is too much that wants to diffuse all at once but there are not enough carriers
