How cholesterol resists changes in membrane fluidity with temperature change?

Answer 1

Adding Cholesterol to a cell membrane reduces fluidity, therefore, making the cell membrane more rigid reducing phospholipid movement. For example, fishes that live in colder waters tend to have less cholesterol content which hinders solidification by disrupting the regular packing of phospholipids. The reason is that in colder waters, they need to have a fluid cell membrane otherwise they would freeze to death. On the other hand, a tropical fish needs to maintain a certain level of rigidity due to the temperature which tends to be warmer in tropical waters, so increasing their cholesterol in cell membranes makes their cell walls more resistant to the heat and denaturing.

Because of the way cholesterol is shaped, part of the steroid ring (the four hydrocarbon rings in between the hydroxyl group and the hydrocarbon "tail") is closely attracted to part of the fatty acid chain on the nearest phospholipid. This helps slightly immobilize the outer surface of the membrane and make it less soluble to very small water-soluble molecules that could otherwise pass through more easily.4

Without cholesterol, cell membranes would be too fluid, not firm enough, and too permeable to some molecules. In other words, it keeps the membrane from turning to mush.

While cholesterol adds firmness and integrity to the plasma membrane and prevents it from becoming overly fluid, it also helps maintain its fluidity.

At the high concentrations it is found in our cell's plasma membranes (close to 50 percent, molecule for molecule) cholesterol helps separate the phospholipids so that the fatty acid chains can't come together and cyrstallize.5

Therefore, cholesterol helps prevent extremes-- whether too fluid, or too firm-- in the consistency of the cell membrane.

Answer 2

By interrupting the continuity of the phospholipids, cholesterol will lower the freezing point of the membrane. However, organism inhabiting colder climates have evolved unsaturated fatty acid chains in the membrane which leads to increased fluidity. This is the main method of ensuring the membrane does not freeze.

Answer 3

It is cholesterol that causes the fludity of the plasma membrane. The incorporation of cholesterol in a diet is highly important, because cholesterol gives the membrane the fluidity and consitency of vegetable oil. This consistency allows the proteins within the membrane to move around as necessary for them to perform their jobs correctly.

Answer 4

Cholesterol is found in every cell of your body. It is especially abundant in the membranes of these cells, where it helps maintain the integrity of these membranes, and plays a role in facilitating cell signaling-- meaning the ability of your cells to communicate with each other so you function as a human, rather than a pile of cells.

Molecule for molecule, cholesterol can make up nearly half of the cell membrane.1 Since it is smaller and weighs less than other molecules in the cell membrane, it makes up a lesser proportion of the cell membrane's mass, usually roughly 20 percent.2

Cholesterol is also present in membranes of organelles inside the cells, although it usually makes up a smaller proportion of the membrane. For example, the mitochondrion, the so-called "power-house" of the cell, contains only three percent cholesterol by mass, and the endoplasmic reticulum, which is involved in making and modifying proteins, is six percent cholesterol by mass. 3

Answer 5

cholesterol resists changes in membrane fluidity with temperature changes due to its steriod rings being bulky and they increase the density of the hydrophobic section of the phospholipid bilayer membrane.