A bacterium is unable to regulate the amount of water it absorbs. What structure of the cell is not functioning properly?

Question

hello, i am sorry to bother, but i am currently taking a test and am epic-ly failing at it, lol. this is the question I have struggled with the most so far!

Answer 1

Hi Cylia!

The key to answering this question is to ask yourself, "What is supposed to regulate what goes into and out of a cell?" The main answer would be "The cell membrane" (also known as the plasma membrane).

The cell membrane has multiple names and terms associated with it. As Alexis pointed out, it is also sometimes called the semi-permeable membrane, but it also sometimes called the lipid bilayer.

Some substances can straight pass through the cell membrane (if they are small and non-polar/hydrophobic), but otherwise, they will need a transport protein. Why is this? The cell membrane is made up of two layers of phospholipids. The phospholipids have a polar, phosphate head facing towards water while the non-polar, fatty acid tails are hydrophobic and will face towards each other to get away from water (hydrophobic = can't stand water/afraid of water). If a substance is non-polar and small, it will be able to pass through that hydrophobic interior.

Water is a polar substance, and so it is not able to pass straight through the cell membrane. Because water is polar, it will not want to be near the hydrophobic, non-polar, fatty acid tails on the interior of the cell membrane. Water needs special proteins in order to allow it into or out of the cell.

However, let's imagine that there is a tear in the cell membrane. That would be terrible for a cell! Since the cell membrane is a fence that controls what goes in and out, now there is no way for the cell membrane to do that! Too much water can flow in or out. Too many ions and nutrients could flow in or out. The bottom line is if there's an issue with the cell membrane, the cell is no longer able to control what goes in or out of it, including water.

If you need any more help, please feel free to ask! Have a wonderful day!

-Leah

Answer 2

Hi Celia!

It seems as if you're struggling to identify which portion of the bacterium regulates water influx. The structure that does this is called the semi-permeable membrane. Semi-permeable means that the membrane will only let certain molecules through, and the membrane is the outermost portion of the bacteria cell. The membran intakes water via osmosis, which allows water molecules to passively diffuse from the outside of the cell to the inside of the cell, or vice versa!

If you have any more questions, or would like to get tutored for biology, please reach out to me through Wyzant! I'm happy to help you succeed!

-Alexis