Electrochemical Gradients Flashcards
(39 cards)
What is diffusion?
Movement down concentration gradient
Diffusion is the process by which molecules move from areas of high concentration to areas of low concentration.
What is simple diffusion?
Molecules move spontaneously from regions of high to low concentration
Simple diffusion occurs without the need for energy or assistance from proteins.
What happens to the concentration gradient over time?
Concentration gradient dissipated
This process increases entropy, aligning with the 2nd Law of Thermodynamics.
What is the role of membranes in diffusion?
Ions cannot cross lipid bilayers
Membranes create a barrier that can lead to different ionic concentrations on either side.
What occurs when a membrane is punctured?
Ions flow down gradient until concentrations equal on both sides
This process establishes equilibrium.
What facilitates diffusion through membranes?
Molecules that punch holes in membranes
These molecules are essential for allowing ions to pass through lipid bilayers.
What are the types of transport proteins involved in ion movement?
- Primary transporters (e.g. Sodium pump)
- Secondary transporters (e.g. Sodium calcium exchanger)
- Ion channels (e.g. potassium channels)
These proteins are crucial for the movement of ions across membranes.
What influences the movement of ions in liquids?
Thermal agitation
Molecules in liquids are in constant motion due to thermal energy.
Who demonstrated the relationship between the number of molecules moving across an interface and the concentration gradient?
Adolf Fick
Fick’s laws of diffusion describe how molecules move across interfaces.
What is the diffusion coefficient?
Proportionality constant in Fick’s laws
It indicates how quickly molecules diffuse across a surface.
How does diffusion vary in different dimensions?
- 1D diffusion: t = d² / 2D
- 2D diffusion: t = d² / 4D
- 3D diffusion: t = d² / 6D
Time depends on the dimensions in which the molecules are diffusing.
Why do molecules diffuse further in three dimensions?
Lower chance of bumping into each other
In three dimensions, molecules have more space to move without collisions.
What enhances the interaction of signaling molecules in membranes?
Catalysts providing a surface for bumping into each other
So signalling molecules in membranes have more chance of interacting —> signalling molecules have longer ranges if they are not bound to membranes (3D)
What is electrophoretic movement?
Ion movement under the influence of an electric field
This phenomenon occurs in solutions like sodium chloride.
What is the electrochemical gradient?
Total gradient of diffusion minus electrophoretic movement
It determines the direction and rate of ion movement across membranes.
What determines the direction of ion movement through ion channels?
Electrochemical gradient
Ions will move in or out of the cell based on this gradient.
What are the four key factors affecting the rate of ion movement across membranes?
- Size of the electrochemical gradient
- Nature of the ion
- Number of open ion channels
- Properties of the ion channel
These factors collectively influence how quickly ions can pass through a membrane.
What is current in the context of ion movement?
Flow of ions
Current refers to the movement of charged particles, such as ions, through a conductor.
What is the effect of a big current?
Many ions flowing per second
What is the effect of a small current?
Few ions flowing per second
What is voltage?
Potential difference = gradient between the two areas
Can’t get ion flow unless there is a potential difference
What is required to get ion flow (current)?
A potential difference
What happens when resistance is low for the same voltage?
Get bigger currents
What happens when resistance is high for the same voltage?
Get smaller currents
