No. A plasma membrane has a whole lot of other stuff in there such as proteins, glycolipids, and (if it's an animal cell) cholesterol. We often think of it as if the plasma membrane is just a phospholipid bilayer, but it's more complex than that.
I'd like to add to Eric Vene [ https://www.quora.com/profile/Eric-Vene ]'s great and concise answer (which is, of course, correct). I'm guessing that for your purpose, you might say that the plasma membrane is a lipid bilayer (it is, there is just, as Eric mentions, more to it as well).
But it is important to note (forgetting for a minute that the membrane contains more than just the lipid bilayer) that only the lipid bilayer surrounding the cytoplasm (that is, the "edge of the cell") is called the plasma membrane. Other membranes surrounding organelles are also lipid bilayers, and they often fuse and pinch off from the plasma membrane. But they are not plasma membrane. When e.g. an endosome [ https://en.wikipedia.org/wiki/Endosome ] pinches off from the plasma membrane, one nanosecond it is (part of) the plasma membrane, the next it is not. By definition, not because the composition of this part of membrane has changed during that nanosecond.
So while the plasma membrane is always (in part made from) lipid bilayer, lipid bilayer is not always (part of) the plasma membrane. So even for the purpose that I (presumptuously) think you need this for, no, you cannot equate the two. The "arrow" in that equation only goes one way.
2 layers of phospholipid is called "phospholipid bilayer". And now to the point, plasma membrane is made up of phospholipids, it can be multi or single layered. So, these both are way different things.
Like all other cellular membranes, the plasma membrane consists of both lipids and proteins. The fundamental structure of the membrane is the phospholipid bilayer, which forms a stable barrier between two aqueous compartments.
read more..
https://mammalssite.blogspot.com/2022/10/plasma-membrane.html
The phospholipids in the plasma membrane are arranged in two layers, called a phospholipid bilayer. As shown in Figure below, each phospholipid molecule has a head and two tails. The head “loves” water (hydrophilic) and the tails “hate” water (hydrophobic).
%3E How exactly does a phospholipid membrane work? Short answer: Whoa! Slow down … Start with reading (e.g.) Wikipedia article Phospholipid Membrane! [ https://en.wikipedia.org/wiki/Lipid_bilayer ]
Exactly? Asking some Quoran to condense several shelf meter worth of highly technical biological papers, journals, and textbooks into an easily digestible Quora answer is not very realistic (let alone “exact”) …
For a far from complete “one image viewer’s digest,” see my animated PowerPoint presentation Cell Membranes — Living Walls .ppsx! [ https://app.box.com/s/4v6bn1tjk195vdwykoe3zpfyejh11g5i ]
See also Google Image Query Phospholipid Membrane [ https://www.google.com/search?biw=1334&bih=635&tbm=isch&sa=1&ei=b73BWqryI8eQ0wKRmJigAg&q=Phospholipid+Membrane&oq=Phospholipid+Membrane&gs_l=psy-ab.3..0l5j0i30k1l2j0i5i30k1l2j0i8i30k1.12368.14990.0.18571.8.8.0.0.0.0.292.1693.2-6.6.0....0...1c.1.64.psy-ab..2.6.1688....0.DTbK80DRduI#imgrc=jhldfzJdy-gr0M ] — the image below was lifted from the first hit (out of thousands):
Cell Membrane Structure image lifted from teachmephysiology.com [ http://teachmephysiology.com ] article Structure of The Cell Membrane. [ http://teachmephysiology.com/basics/cell-structures/cell-membrane/ ]
Is your test on the subject tomorrow? Good Luck!
Because it’s composed of two layers of lipids (fats) and phosphates. The stem word “Bi” means two. Phospho correlates to phosphates. Hope that makes it easier to break down later! Here is a good example of the structure without getting into the chemistry of it:
Lipids are molecules that contain hydrocarbons and make up the building blocks of the structure and function of living cells. Inorganic phosphate is an essential building block of cell membranes, DNA and proteins. Living cells use phosphate to transport cellular energy with adenosine triphosphate (ATP), necessary for every cellular process that uses energy. ATP is also important for phosphorylation, a key regulatory event in cells. Bilayers are particularly impermeable to ions, which allows cells to regulate salt concentrations and pH by transporting ions across their membranes using proteins called ion pumps.
Depending upon whether you are looking for the particular substance, or the specific nature of the plasma membrane, would determine the correct answer.
The plasma membrane has some fluidity simply due to the presense of the fatty acid tails between the polar heads in the bilayer.
However, if you're looking for the specific substance that is within the bilayer in animals and impacts fluidity, that should be cholesterol.
Cholesterol has the ability to act as a type of buffer and can regulate fluidity both in warmer and colder temperatures compared to normal environment temperature. Simply put, when a membrane is at high temperatures, the presence of cholesterol raises the melting point which stabilizes the structure. When at colder temperatures, the presence of cholesterol between the phospholipids prevents them from stiffening.
I hope this is the answer you were looking for!
All the best,
Taylor
Prokarotic membranes have only a few types of phospholipids while eukaryotic membranes have can have over 6 different phospholipids as well as other types of lipids. Prokaryotic membranes do not commonly have cholesterol inside the hydrophobic core whereas eukaryotic membranes use chloresterol to regulate their fluidity.
Cell Membrane:-
The cell membrane is a type of plasma membrane that encloses the entire contents of a cell, including the cytoplasm and all the organelles.
The cell membrane is not always the outermost layer of the cell since plant cells also have a cell wall that further encloses the cell membrane.
Animal cells however have no cell wall and the cell membrane is the barrier between the inner contents of the cell and the external environment.
The cell membrane consists of a phospholipid bilayer that also contains integral proteins. Integral proteins often span the membrane and provide pathways for molecules to move through the membrane.
Plasma Membrane:-
The plasma membrane is a membrane that surrounds individual organelles or the contents of a cell. The cell membrane is a type of plasma membrane that encloses the cell.
There are plasma membranes found surrounding both the cytoplasm and contents of a cell and surrounding individual organelles such as chloroplasts and mitochondria.
This means that plasma membranes have several different functions depending on where they are located.
The structure of the membrane can vary depending on what it surrounds, whether that is the entire cell or an organelle in the cell.
