Question

1. A concentration gradient affects the direction that solutes diffusion. Describe how molecules move with respect to the concentration.
2. How does size affect the rate of diffusion?
3. Does polarity affect the rate of diffusion? Explain your answer.
4. If a piece of celery is placed in a glass of pure water, are the celery cells hypertonic, hypotonic or isotonic compared to the water? In which direction will water move?
5. What is the water potential of pure water?
6. Why don’t red blood cells swell or shrink in blood plasma?
7. Research how osmotic power plants work. Summarize what you learned in 1-2 paragraphs. Include references to information sources used.

Answer 1

Ans- The direction of the movement of solute will be down the concentration gradient during diffusion. Diffusion moves molecules from an area of high concentration to an area of low concentration unless the concentration gradients are equalized. The rate of diffusion depends on the size of the particles because of the membrane permeability factors. The larger molecules diffuse slower than smaller molecules. A very large molecule will be unable to diffuse through the pore of the membrane and hence stops the process of diffusion.

Ans- Yes, polarity of molecules affect the rate of diffusion. Phospholipid bilayers have hydrophilic heads and hydrophobic tails. They can chemically allow small non-polar molecules to freely diffuse. This process is termed as passive transport. However, phospholipid bilayers does not allow the passage of hydrophilic molecules by Passive transport. This is because, they will be repelled when they encounter the hydrophobic tails of the membrane.

Ans-If a piece of celery is placed in a glass of pure water, the cells will be hypertonic( more solute inside the cells) as compared to the water. Hence, in order to maintain equilibrium, water will flow into the cells.

Ans- The water potential of pure water is zero in the glass since, pure water has no solute and the pressure in the glass is also zero.