Questions tagged [cell-membrane]

A selectively-permeable biological membrane that separates the interior of all cells from the outside environment.

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Why does the cell membrane need hydrophilic heads?

I was just learning about the phospholipid bilayer and it appears that the hydrophobic tails are basically the "impenetrable" part; as in non-polar molecules are allowed in because they ...
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If a chemical passes through the blood-brain barrier does that mean it will pass through the membranes of most cells?

For instance, there is a drug that I heard will pass through the blood brain barrier and I wanted to know if I could infer from this that it would readily enter the cytoplasm of cells elsewhere in the ...
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Is raw meat or raw vegetables easier for humans to digest?

Which one is easier for a human digestive system to digest, raw meat or raw vegetables? I have heard some of my friends who say that raw (or uncooked) meat is easier to digest than raw (or uncooked) ...
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Why do the phosphatidylserine and Phosphatidylethanolamine favor one side of the cell membrane?

Thie picture below shows that the phospholipids phosphatidylserine (PS) and Phosphatidylethanolamine (PE) are more likely to be found on the inside of cell membranes than on their exterior. Why is ...
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Sodium-potassium pump (Na+/K+) time limit, endless without action potential?

As written in Wikipedia: The sodium–potassium pump mechanism moves 3 sodium ions out and moves 2 potassium ions in, thus, in total, removing one positive charge carrier from the intracellular space. ...
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Can cell adhesion molecules have intrinsic enzymatic activity?

I am learning about cell adhesion molecules (CAMs), and I know that they mediate cell-cell and cell-extracellular matrix adhesion via homophilic and heterophilic interactions. I have read that CAMs ...
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Why does secondary active transport occur in the companion cell during active loading of sucrose into the sieve tube element?

So, during the active loading of sucrose into the sieve tube element from the companion cell, hydrogen ions are pumped outside the cell by active transport through carrier proteins. The high ...
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Can some bacteria eat soap molecules in soapy water rather than get killed by it? How do they hang on to their surface lipids? Evolutionary advantage?

In my Chemistry SE question Quantifying soapiness; there's pH, pKa and pO2, is there a p_soap or p_surfactance? I explained that when I am too lazy or too much in a hurry to do my dishes right away I ...
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What mechanism causes the presence of photosensitizers in mitochondria to change membrane ionic currents?

In the original question, the article in question was talking about specifically about this compound, Benzoporphyrin: Characterization of Perturbing Actions by Verteporfin, a Benzoporphyrin ...
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Do the cadherins involved in adherens junctions and the cadherins in desmosomes "communicate" at all?

I think I have a basic understanding about the function of these cytoskeleton-linked junctions, and they can link one cell to another and the interaction of cadherins of adjacent cells give the ...
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How much MPa of pressure can human cells survive?

Is there any research on this topic with concrete numbers? I found some papers of high pressure tests on microbes, but not on human/mammal cells. What I want to find is true "crush depth" ...
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What is silicalemma and what is plasmalemma in diatom algae and how do they differ?

I try to understant the morphology (cytology?) of diatom algae. Does someone can describe what is silicalemma and what is plasmalemma in diatoms and how do they differ? Or they are the same?
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Are living cells electrically neutral?

I found random scientific table which had a comment attached: the cells must be electrically neutral. Per my knowledge whole intracellular solution contains more electrons than protons (definition ...
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Why does the time to reach equilibrium across a membrane decrease with concentration?

We're learning about flux and Fick's law and there's one point I'm having trouble understanding. Assuming we have a higher concentration of a species on one side of a membrane, I understand that ...
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At what calcium concentration does the Sodium-Calcium Exchanger (NCX) "turn on"?

I am interested in the comparison between the Plasma Membrane Calcium ATPase (PMCA) and the Sodium-Calcium Exchanger (NCX) which are two pumps on the plasma membrane of cells that serve to move ...
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Why/How can Hydrophobic things pass the lipid bilayer? [duplicate]

I’m just looking for a simple answer for this question. I’m in Bio 10, and don’t know the in depth stuff. So the lipid bilayer is hydrophilic and the ends, but hydrophobic in the middle; so how can ...
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Will plant cells absorb "atypical" chemicals dissolved in water, by diffusion or otherwise?

I want to know what determines whether a chemical dissolved in water, will or will not be absorbed into a plant. I imagine this can happen at a few different levels -- through roots, or at a cellular ...
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How do transmembrane proteins bind to specific locations on the membrane?

Taking a specific case, how do some GPCRs only bind to dendrites and others only to the axon terminals (reuptake receptors)?
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Why can't H3O+ ions pass through aquaporins?

Aquaporins are proteins that facilitate the movement of water (and related molecules) through cell membranes. (Also, these transport proteins are very specific about what they transport.) ...
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Types of structures formed by various types of lipid molecules

Since Phosphatidylcholine (PC) and phosphatidylserine (PS) are roughly cylindrical in shape , they tend to form flat bilayers. Phosphatidylethanolamine (PE) on the other hand is conical in shape which ...
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When transmembrane proteins destined for the plasma membrane are in the ER membrane are they in their final folded form?

I am studying how transmembrane proteins are made and I have read that proteins that are destined for the plasma membrane are initially in the ER membrane and do not get translocated into the ER lumen ...
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Can proteins be located on the surface of the mitochondria?

I am learning about the mitochondria and I know there are proteins present in the mitochondrial matrix such as SOD2, but I was wondering for a protein to be located on the surface of the mitochondria ...
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Is the phrase "transmembrane segment" equivalent to the transmembrane domain of a protein?

I am reading the Handbook of Neurochemistry and Molecular Neurobiology and I am learning about the cell adhesion molecule NCAM2 and I have come across the following: The overall structure of NCAM2 ...
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What is meant by "opposing plasma membrane" with respect to cell adhesion molecules?

I am reading the Handbook of Neurochemistry and Molecular Neurobiology and I am learning about cell adhesion molecules (CAMs) and I have come across the following: CAMs are involved in homo‐ or ...
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What fraction of bacterial proteins are membrane bound?

Almen et al. showed that around 27% of the human coding proteins are membrane bound. How does this compare with bacteria such as E.coli or B.subtilis (or any other bacteria)? Is there a paper out ...
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How fast do lipids on the inside and outside of a lipid bilayer exchange?

Biological membranes normally have different composition of lipids on the inside and outside (ref 1, ref 2). This is maintained both by how new lipids are added to membranes, and by specialized ...
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Can high energy photoelectrons damage cell membranes?

I've read that in addition to ionizing radiation causing damage to DNA through direct absorption, but DNA can also be damaged through photoelectrons with enough energy. The thing I was wondering is ...
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Why doesn't the concentration of one ion affect the concentration gradient of another ion across a plasma membrane?

In the initial stages, some ion channels across the plasma membrane open to allow for ions to flow down their concentration gradient into or out of the cell. I understand that each ion's overall ...
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4 votes
1 answer
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Why don't weak detergents lyse the nuclear membrane?

A low concentration of a non-ionic detergent lyses the cell membrane, but leaves the nuclear membrane intact. Both are phospholipid bilayers, so why is only the cell membrane lysed? Under these ...
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1 answer
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What's a cells membrane potential without any leak channels?

Consider the following ion concentrations on either side of a cell membrane (in = inside cell, out = outside cell): $[\text{Na}^+]_{\text{in}} = 10mM$, $[\text{Na}^+]_{\text{out}} = 142mM$, $[\text{K}^...
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Why doesn't the polar side of the plasma membrane block nonpolar diffusion?

It is often stated that small molecules or nonpolar molecules can diffuse through the plasma membrane because they can pass through the middle nonpolar bit, but why don't the polar sides block these ...
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What are the differences in ultrastructure of cilia and flagella?

Cilia and flagella are aimed for similar perpose, motion. And both of them show the (9+2) microtubule arrangement. They are nearly identical in structure. But to be more specific , where exactly does ...
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Giving a sign to Pressure Potential, Osmotic Potential And Other Similar Quantities

When these quantities are mentioned with what reference do we give signs to them? Why is Osmotic Pressure positive, but Osmotic Potential, negative? What about Turgor Pressure (Pressure exerted by the ...
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How is the cell membrane protective?

Generally in biology books, it is written that the cell membrane is selectively permeable and that it has a protective function, as in here It says that the cell membrane protects the cell from its ...
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Effect of opposing electric charges on cells

Is the affect on a cell between two negatively charged plates theoretically similar to between a positively and negatively charged plate? In other words, would it induce charges on the inside and ...
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Do SARS-CoV-2 virus particles really travel through filopodia and "emerge from the tips"?

Watching the new University of California San Francisco video Coronavirus forces cells to produce tentacle-like structures that infect neighboring cells I saw The growths spread out, and ...
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2 votes
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What is the exact definition of mitochondrial depolarization?

As I understand as per literature reading and some khanacademy(https://www.youtube.com/watch?v=PtKAeihnbv0&t=315s): Proton gradient := the gradient created when hydrogen ions moves to the ...
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4 votes
1 answer
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How does the DNA cross through bacterial cell wall during electroporation?

There exists a lot of literature on electroporation of Gram-positive and negative bacteria. Most of it gives an explanation that electroporation works by creating transient pores in cell membranes of ...
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Why does insertion of transmembrane domains occur in the rough ER?

To elaborate on that question, why in the secretory pathway does the insertion of transmembrane domains into the membrane occur in the rough ER as the protein is translated and threaded across the ER ...
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1 answer
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Why viruses "die" outside the host? [duplicate]

Why viruses "die" outside the host after sufficient time? I want to know the biological process behind it. What role being exposed to air plays in virus destruction? What role sunlight plays in the ...
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Does the cell release the empty capsids?

The virus via the spike of the capsid connects to a receptor in a cell, then the DNA enters the cell wall. My question is what happens to the capsid - does it stay connected to the receptor or is ...
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What is the lipid membrane of SARS-CoV-2 made of?

SARS-CoV-2 is an enveloped virus: in structural diagrams it is drawn with membrane glycoprotein (M), envelope protein (E) and spike protein (S) embedded in a lipid membrane. What specifically is the ...
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What are the short/long term effects of chloroquine on fundamental cell processes?

Does chloroquine, which affects the endosomal membrane traffic pathway (by affecting the acid environment used for fundamental endosomal reactions), have short/long-term effects on cell growth/...
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3 votes
1 answer
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Proteoglycans vs Glycoproteins

On the left, is my histology book, on the right there's qoura (the internet). My histology textbook says that "unlike glycoproteins, proteoglycans have attached GAGs which often comprise a greater ...
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Help me understand voltage patch clamping

Before I type my question it is important to know that I already tried looking this up on my own and could not find an answer because the answers are all in complicated physics terms and this topic is ...
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Why don't carrier proteins require energy to change shape?

I know that carrier proteins can be used for both passive and active transport, but I am referring to the facilitated diffusion aspect. Even though facilitated diffusion via carrier protein goes along ...
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Are ligand gated channels saturable?

A major difference between simple diffusion and facilitated diffusion is that facilitated diffusion has a maximum transport and velocity; the rate of diffusion is limited, whereas in simple diffusion, ...
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How does a protein molecule enter a cell through the cell membrane? [closed]

I can't find a good explanation as to how a whole protein molecule enters a cell membrane. Is it through endocytotic vesicles, with the help of ATP? How does this occur? Thanks for the help!
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3 votes
1 answer
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How are lipid-coated mRNA-based vaccines transported into cells for expression?

In CNN's video Scientist says Coronavirus vaccine could be ready by 2021 after about 00:25 'Robin Shattock, the Head of Mucosal Infection and Immunity at Imperial ...
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How are newly synthesised proteins targeted to the plasma membrane?

There does not seem to be a definitive answer to how proteins destined to be intrinsic plasma membrane proteins are directed there. Presumably, assuming starting at a cytosolic ribosome, the pathway ...
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