Diffusion And Facilitated Diffusion Flashcards
What is the definition for diffusion.
The net movement of molecules or ions from an area of high to low concentration until equilibrium is reached.
Move down a concentration gradient.
Explain how diffusion across a membrane can occur.
Most molecules cannot pass easily through cell surface membrane. However, small, non-polar, lipid soluble molecules can diffuse through the bi-layer.
What are the factors that affect are of diffusion
Temperature
Length of diffusion pathway
Concentration gradient
Area for diffusion
How does temperature affect rate of diffusion
An increased temperature increases the rate of diffusion as the particles gain more kinetic energy
How does length of a diffusion pathway affect rate of diffusion ?
A shorter diffusion pathway increases the rate of diffusion because there is less distance to diffuse across.
How does concentration gradient affect rate of diffusion ?
A larger gradient increases the rate of reaction because there is a greater difference between the inside and outside of cells.
How does area affect rate of diffusion.
A larger surface area created an increased rate of diffusion because there is more membrane for diffusion to occur.
When is facilitated diffusion necessary.
When molecules cannot diffuse through the bi-layer.
What is facilitated diffusion?
Proteins embedded in the phospholipid bi-layer allow molecules and ions to pass through the cell ( channel and carrier).
How do channel proteins carry out facilitated diffusion and with what type of ions ?
Move smaller, water soluble ions and act as a gate by only opening for specific ions.
Ions bond to the protein causing it to change shape and opening the channel.
Ions diffuse through the channel from high to low concentration.
What ions or molecules do channel proteins assist in facilitated diffusion ?
Sodium , potassium , chlorine
How do carrier proteins aid facilitated diffusion ?
They move larger molecules by changing shape when they bind to them.
The proteins are specific to certain molecules.
Molecules diffuse through the carrier protein from an area of high to low concentration.
Give examples of ions or molecules that carrier proteins move via facilitated diffusion.
Glucose
Amino acids
Neurotransmitters
Name some features of simple diffusion
No carrier protein required
Passive - no energy required
Only very small molecules such as oxygen and lipid soluble molecules such as steroid diffuse.
Give some features of facilitated diffusion.
Requires a carrier protein
Large and polar (charges molecules) diffuse in this way.
Passive - no energy required.
What is Fick’s law ?
(Surface area x concentration gradient) / diffusion distance.
Bigger on top is better.
Smaller on bottom is better.
Name one lipid soluble substance.
Steroids
What type of molecules are carried in facilitated diffusion.
Large polar molecules which are charged.
What type of diffusion occurs with Carbon dioxide to move into a cell and why ?
Carbon dioxide are non-polar, small molecules which means that normal diffusion occurs. Diffusion is a passive transport method with a movement from high to low concentration.
What type of diffusion is used for glucose and why ?
Glucose uses facilitated diffusion due to being a large polar molecule. A protein is require for this.
The disc shape of glucose also allows a larger surface area to volume ration and shortens the diffusion pathway leading to faster reactions.
Describe how proteins are arranged in a plasma membrane and the part they play in transporting substances in and out of cells.
Intrinsic proteins pass right through the membrane. They are involved in facilitated diffusion and active transport as they act as protein carriers.
Carrier proteins change shape and position where as channel proteins have hydrophilic pores.
Proteins allow the passage of water soluble molecules or charged particles.
Explain how the shape of a red blood cell allows it to take up large amounts of oxygen in a short time.
Has a large surface area to volume ration which decreases the diffusion pathway for maximum diffusion.
Why may red blood cells not be seen and appear a uniform pale red colour when placed in a detergent which dissolves lipids ?
The phospholipid bilayer would be dissolved causing haemoglobin leakage.
