Biology transport across membranes

Explain whether a salt solution will have a higher or lower water potential than pure water.

It will have a lower water potential as the water has a lower tendency to move. This is due to the water in the salt solution interacting with the polar salt molecules

What properties do molecules that move by simple diffusion have?

They are non-polar so they can interact with the phospholipid fatty acid tails.
They are small, so they can fit between the fatty acid tails.

What is incipient plasmolysis?

When 50 % of cells are plasmolysed and 50 % of cells are not, because cells have varying water potentials.

Explain 2 factors that affect the rate of facilitated diffusion.

Temperature- a higher temperature means molecules have more kinetic energy so there will be a faster rate of diffusion. Surface area of the membrane- a higher surface area means there is more space for molecules to cross the membrane so there is a faster rate of diffusion. Steepness of the concentration gradient- the bigger difference in concentration the faster the rate of diffusion. Number of protein carriers- the less protein carriers the slower the rate of facilitated diffusion