Awhite starch solution was poured into a length of dialysis tubing and the ends were tied. the tubing was then dropped into the beaker of iodine solution. after 10 minutes, the white starch solution turned black, and the iodine water remained red. what cellular structure was the dialysis tubing most likely representing in this experiment

Cell membrane

Explanation:

The cell membrane is mainly composed of the lipid bilayer and embedded proteins. The hydrophobic core of the cell membrane does not allow the polar, charged, and large substances to move through it freely. However, the non-polar and small substances can diffuse through the membrane. Therefore, cell membranes are semipermeable and regulate the entry and exit of substances from cells.

In the given experiment, iodine molecules from the beaker enter the dialysis tube and turned the starch solution black. On the other hand, the large starch molecules were not allowed to diffuse across the dialysis tube and there was no change in the color of the iodine solution present in the beaker. This represents that the dialysis tube served as a semipermeable membrane and allowed only selected molecules to pass through it.

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.