Membrane Transport - Lecture 3 Flashcards
What are the two properties that influence if a particle can permeate the plasma membrane without assistance?
Lipid solubility
Size
What are the two types of Driving forces ?
Passive - (leak channels)
Active - (Requires the use of ATP to produce movement)
In unassisted membrane transport what are the two forces that passively drive a particle across the membrane?
Electrical Concentration
Concentration Gradient
What is dynamic equilibrium ?
This is were the concentration gradient no longer exists
What is diffusion?
Diffusion is the net movement of molecules into or out of a cell down their concentration gradient
What causes molecules to move from a high concentration gradient to a low
More collisions in the area with the higher concentration, as there are more particles
This causes particles to move from high to low
What are the factors affecting Diffusion?
The magnitude of the concentration gradient
The surface area
The solubility of the substrate
The size of the substance/molecular weight
The Distance though which diffusion must take place
What is fick’s law equation?
Q = Delta C x A x P
Q= rate of diffusion
delta C = Concentration gradient
A = Area of surface
P = Permeability
What is osmosis?
Osmosis is the net diffusion of water down it own concentration gradient
What are the channels through which water moves through called?
Aquaporins
What is Osmolarity?
Osmolarity is the concentration of osmotically active particles present in a solution
(e.g. if the concentration of NaCl is 150 osm there would be 150 Na and 150 Cl - meaning there are 300 osmotically active substance
Osmolarity = No. Particles X Molar Concentration
What is an isotonic solution?
An isotonic solution is one that has the same osmolarity as blood
What is a hypotonic solution?
A hypotonic solution is one that has a lesser osmolarity than blood
What is a hypertonic solution?
A hypertonic solution has a higher osmolarity than blood
How does Carrier Mediated Transport occur?
Substance binds onto a specific carrier which undergoes a conformational change which transports the substance
What are the characteristics that determine material transfer by carrier mediated transport?
Specific to the transporter
Saturation point has not been reached
Competition with the transporter
What form of diffusion allows more substrate to enter the cell?
Facilitated Diffusion
What are the forms of active transport?
Primary Active Transport
Secondary Active Transport
What is Primary Active Transport?
Requires the direct use of energy to move a substance against its concentration gradient
What is secondary Active Transport?
Required energy but does not utilise ATP
Utilises secondary energy stores in the form of ion concentration gradients
What is the purpose of the Sodium Potassium pump ?
Sodium is transported into of cells
Potassium is transported out of cells
How much sodium is transport into cells for Potassium exported?
3 Na+ for 2 K+
What is the purpose of the Sodium Potassium Pump?
Establishes concentrations of Na+ and K+ across the plasma membrane
Helps regulate cell volume
Energy used to drive the pump indirectly serves as the energy source for secondary active
transport
What is a Symport protein transporter?
Used for Secondary Active transport
The Solute and the ion move in the same direction
What is a Antiport protein transporter?
Used for secondary active transport
The solute and ion move in opposite directions ( Ion into, solute out of the cell).
What is Endocytosis?
This is the pinching off of membrane to engulf substance
What is Exoctyosis?
A vesicle fuses with the plasma membrane releasing it contents to the ECF
What is tonicity?
Tonicity is the effect a solution has on cell volume
What occurs at the Transport Maximum of a protein (Tmax) ?
Each carrier can only absorb certain number of molecules per unit time
- This is the Saturation Point
