investigating cell permeability Flashcards
(7 cards)
What is the structure of the cell-surface membrane and how does it relate to permeability?
A: The cell-surface membrane is composed of a phospholipid bilayer, which makes it selectively permeable. This permeability can be affected by external factors like temperature and solvent concentration.
What does a higher absorbance reading in the colorimeter indicate in the beetroot experiment?
A higher absorbance means a higher concentration of pigment in the solution, which indicates greater membrane permeability.
What variables can be investigated in the beetroot membrane permeability experiment?
Temperature and ethanol concentration can be tested for their effect on membrane permeability
Why do we use a blue filter in the colorimeter?
A blue filter enhances the contrast for detecting the red/purple pigment (betalain) and gives more accurate absorbance readings
What happens to membrane permeability as temperature increases?
Permeability increases because membrane proteins denature, creating gaps in the membrane. At high temperatures, the phospholipids become more fluid, making it easier for pigment to leak out.
how to make dilution series
Start with a strong (concentrated) solution, like 1M sugar water.
Take a small amount of this strong solution (for example, 2 ml) and put it into a new container.
Add a certain amount of plain water to it (for example, 8 ml). Mix well. Now you have a weaker solution (0.2M if starting with 1M).
To make the next weaker solution, take the same amount (2 ml) of the 0.2M solution and add the same amount of water again (8 ml). Mix. This makes 0.04M solution.
Keep repeating this: take some of the last solution, add water, mix — each time making the solution weaker and weaker.
example of dilution series with numbers
2 ml sugar + 8 ml water = 0.2 M
4 ml sugar + 6 ml water = 0.4 M
6 ml sugar + 4 ml water = 0.6 M
