Cell transport, uptake and secretion Flashcards
Briefly describe the phospholipid bilayer
- Hydrophilic heads- made up of phosphate, glycerol, and a polar group
- Hydrophobic tails- made up of fatty acids
- 7.5 nm thick
- forms spontaneously in water
What does the rate of diffusion depend on?
membrane thickness, solubility in membrane and difference in concentration of substance
What types of molecules are able to diffuse through the cell membrane?
Hydrophobic molecules can easily pass through the membrane. Small, uncharged, polar molecules can pass through, but less easily
What types of molecules are not able to diffuse through the cell membrane?
Large polar molecules, ions
Name the four ways that molecules are able to pass through the plasma membrane
Simple diffusion
Channel facilitated diffusion
Carrier facilitated diffusion
Active transport
Simple diffusion
Passive transport sufficient to transport small non-polar solutes down their concentration gradient
Channel/carrier facilitated diffusion
Passive transport sufficient for solutes with a low permeability coefficient being transported down their concentration gradient
Active transport
Required for solutes being transported against their concentration gradient
Give another name for carrier proteins
Transporter proteins
How do channel proteins assist with movement?
They weakly interact with solutes, forming pores in the membrane which allow the solutes (usually ions) to diffuse through them.
How do transporter proteins assist with movement?
They specifically bind the solute and undergo a conformational change to release the solute on the other side of the membrane
Describe saturation kinetics
Saturation kinetics describes any reaction or process that has a limiting factor. Initially the rate of transport is directly proportional to how much of the substrate needs to be transported. Once the system reaches saturation, only a fixed amount of substrate can be processed, and the system reaches zero-order kinetics.
