Diffusion Flashcards
What does passive transport mean?
- Energy comes from the natural motion of particles, rather than an external source such as ATP.
- No energy used.
What is diffusion?
• Net movement of molecules or ions from a region where they are more highly concentrated to one where their concentration is lower until evenly distrusted.
What is the concentration gradient?
The path from an area of higher concentration to an area of lower concentration.
How do particles diffuse?
Down concentration gradients
What type of transport is diffusion?
Passive
What energy does diffusion rely on?
• Inbuilt motion ( kinetic energy ) of diffusing molexcules.
What are the two types of protein involved in diffusion?
- Protein channels
* Carrier Proteins
What is simple diffusion?
When molecules diffuse directly through a cell membrane.
Why is oxygen and carbon dioxide able to easily diffuse through cell membranes?
- They are small, they are able to pass through spaces between phospholipids.
- They are non polar, allowing them to be soluble in lipids, so they can dissolve in the hydrophobic layer.
Why are charged particles and ions not able to diffuse easily?
Water soluble, and the centre of the bi-layer is hydrophobic, meaning that they cannot pass through.
How do protein channels work?
- They form water filled hydropillic channels across the membrane.
- They allow specific water soluble ions to pass through
- The ions then bind with the protein, resulting in it changing shape in a way that closes it to one side of the membrane, and opens it on the other.
How are protein channels selective?
- Each channel opens in the presence of a specific ion, if the ion is not present, the channel remains closed.
- This allows control over entry and exit of ions
How do carrier proteins work?
- A large molecule attaches to a carrier protein in the membrane.
- Protein will then change shape.
- This will release it the molecule on the opposite side of the membrane.
Where are carrier proteins present?
They span the cell plasma membrane.
What do carrier proteins transport?
Large molecules
What do protein channels transport?
Ions
What factors affect simple diffusion?
- Concentration Gradient
- Thickness of exchange surface
- Surface area
How does concentration gradient affect simple diffusion?
- Higher concentration gradient is, the faster the rate of diffusion.
- As diffusion takes place, the difference in concentration between two sides of the membrane decreases until it reaches an equilibrium ( concentrations on both sides are equal )
- This also means diffusion slows down over time
Why does diffusion slow down over time?
- Higher concentration gradient is, the faster the rate of diffusion.
- As diffusion takes place, the difference in concentration between two sides of the membrane decreases until it reaches an equilibrium ( concentrations on both sides are equal )
- This also means diffusion slows down over time
How does thickness of exchange surface affect rate of diffusion?
The thinner the exchange surface, the shorter the distance the particles will have to travel, and therefore the faster the rate of diffusion.
How does surface area affect rate of diffusion?
The larger the surface area, the faster the rate of diffusion.
What factors affect rate of facilitated diffusion?
- Concentration Gradient
* Number of channel or carrier proteins.
How does the number of channel/carrier proteins affect rate of diffusion?
Once all the proteins in a membrane are in use, facilitated diffusion can’t happen any faster, the greater the number of channel or carrier proteins in the cell membrane, the faster
