Respuesta :
D. Unlimited flow of water into or out of the cell
Let's take a look at the options and see what does and does not make sense about what the cell membrane prevents.
A. Unlimited flow of heat into or out of the cell
* Preventing the flow of heat requires insulation and generally, the thicker the insulation and less material used in the insulation improves its capability. Cell membranes are entirely too thin and have too much mass for their size to be an effective thermal insulator. So this is a bad choice.
B. The flow of oxygen into or out of the cell
* I hope this is obviously wrong. If oxygen couldn't get into the cell, then life as we know it wouldn't exist. Our biology requires oxygen in order for our metabolism to work. So this too is a bad choice.
C. The flow of light into or out of the cell
* Go outside during the day and hold your hand between your eyes and the sun. Do you see anything through your hand like perhaps a reddish color? If so, that's a pretty solid demonstration that light can pass through the cell membrane. So this too is a bad choice.
D. Unlimited flow of water into or out of the cell
* Now we're getting somewhere. Water does need to pass through the cell membrane, but we can't have unlimited flow. The cell needs to have a proper balance of molecules suspended in water inside. Too much water is bad, too little water is also bad. The cell membrane helps regulate the water content within the cell, so this looks like the only good choice.
D. Unlimited flow of water into or out of the cell
Further explanation
Cell membranes are a universal feature shared by all types of cells in the form of interface layers called plasma membranes, which separate cells from the environment outside the cell, especially to protect the cell nucleus and the survival system that works inside the cytoplasm.
In eukaryote cells, the cell membrane that encloses the organelles in it, is formed from two kinds of compounds namely lipids and proteins, generally of phospholipid type such as compounds between phosphatidyl ethanolamine and cholesterol, which form structures with two layers with certain permeability so that not all molecules can pass through cell membrane, but on the sidelines of the phospholipid molecule, there is a transporter which is a pathway in and out of substances that are needed and not needed by the cell.
Water permeability values in multiple membranes of various lipid compositions range from 2 to 1,000 × 10−5 cm2 / s. The highest rates are found in plasma membranes in renal epithelial cells, some glia cells and some cells that are affected by membrane proteins of the type of aquaporin. Aquaporin-2 allows the presence of water transporters that are sensitive to vasopressin, while the expression of aquaporin-4 is found to be very high in some glia and ependimal cells.
The components of cell membranes include phospholipids, proteins, oligosaccharides, glycolipids and cholesterol.
One of the functions of cell membranes is as molecular and ionic traffic in both directions. Molecules that can pass through cell membranes include hydrophobic molecules (CO2, O2), and very small polar molecules (water, ethanol). Meanwhile, other molecules such as polar molecules with large size (glucose), ions, and hydrophilic substances require special mechanisms to be able to enter the cell.
The large number of molecules entering and leaving the membrane causes the creation of membrane traffic. Membrane traffic is classified into two ways, namely by passive transport for molecules capable of passing through the membrane without special mechanisms and active transport for molecules that require special mechanisms. Membrane traffic will make a difference in ion concentration as a result of two different processes namely diffusion and active transport, known as ion gradient. Furthermore, the ion gradient makes the cell has a cellular electrical voltage.
Learn More
Cell membranes : https://brainly.com/question/6676567
Details
Class: middle school
Subject: social studies
Keywords : cell membranes, functions, organelles
