Lab 1 

Passive Transport

Cells maintain homeostasis by passive and active transport across their membranes. Study the diagrams of the beakers to the right, noting the concentrations of various substances in the beakers and in the cellulose bags. Water molecules can pass through the cellulose, but starch cannot. Draw arrows in the diagram to show the directions in which water will move. Then, answer the questions that follow.

1.   What do the cellulose bags represent?

the plasma membrane

2.   Which of the beakers contains a solution tat is hypertonic relative to the bag’s contents?

Beaker #2

3.     What will eventually happen to the concentrations in beaker 2?

 Eventually, the solution outside the bag will reach equilibrium with the solution inside it. They will be isotonic. Water will diffuse through the bag until the solution in beaker #2 is 90% water

Lab 2 (1 point)

2. A mature human red blood cell has no nucleus or mitochondria and is biconcave. It consists primarily of a membrane surrounding hemoglobin, the protein molecule that carries oxygen. Suggest an advantage of the simple organization of human red blood cells. How does structure meet function? Explain in 6-7 lines.

 The biconcave shape of red blood cells ensures a large surface area for gas exhange. Each hemoglobin molecules in the cells are close to the surface. The are about 270 million hemoglobin molecules so there must be a high surface to volume ratio. They are also very small so they can bend over themselves and move through capillaries. Without blood to the capillaries, tissues would not receive oxygen and warmth, and would die.