Questions tagged [cell-membrane]

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

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Movement of solutes across a semipermeable membrane in a U-shaped tube

The solutions in the two arms of this U-tube are separated by a membrane that is permeable to water and glucose but not sucrose. Side A is half-filled with a solution of 2 M sucrose and 1 M glucose. ...
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Does the molecules in nerve cell membrane change 100% during the life of the nerve cell?

In their lifespan nerve cells do not divide and so they stay the same. They do get damaged sometimes and require some maintenance and change their axons a bit. They also require a lot of energy so ...
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Why is the ordinary cardiac muscle’s target value of the action potential 0mV?

Why do some excitable cells have a target of 0mV for the action potential, even with a slight overshoot? Excitable cells such as muscles and nerves have the ability to rapidly change their membrane ...
Blue Various's user avatar
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Examples of mechanisms of metabolic trapping inside cells that create concentration gradient

I am looking for examples in biology in which a metabolite that can diffuse freely across a cell membrane (through passive diffusion), once inside, gets modified to a form that cannot diffuse back ...
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In what sense is Syringammina single-celled?

In what sense is Syringammina single-celled? For example, if it's true that all cells have membranes (is it?), then how do you identify its membrane? Or does unicellular simply mean that it has only ...
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What are the key mechanisms of control and transport of ATP from mitochondria to synapse in active firing neurons?

I am working with a group in the field of neuronal activity (in computational neuroscience), in specific the firing rates at different ensemble/population hierarchies. It is well established that ...
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What is the difference between a semi-permeable membrane and a selectively permeable membrane?

What is the difference between a semi-permeable membrane and a selectively permeable membrane in cell biology? Is a selectively permeable membrane a type of semi-permeable membrane? Please help. I ...
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What lysis buffer recipe is good for just breaking the cell membrane?

I am interested in the decellularization of plant leaves(more specifically maple) and thus need a lysis buffer. I want the buffer to only break the cell wall and cell membrane and I want to observe ...
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Boundary of a cell and its membrane - position definition and jargon problem

Can extracellular be extramembrane/intramembrane? Definition of Extracellular here: Extracellular matrix: The extracellular matrix is a complex network of material such as proteins and ...
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electrotonic spread and screening

(In physics.stack I have been suggested to post my question also here.) In the classical theory of passive neurons (where the action potential is not yet excited), the voltage is successfully ...
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Naming the Rings of Flagellar Structure

I will apologise ahead of my very basic question. I just read about Flagella Structure and learned that there are 4 rings, namely "L Ring", "P Ring", "MS Ring", "C ...
green onion's user avatar
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Why can't protein pumps reuse phosphate groups?

I am currently in AP Bio, and our textbook has a diagram of a sodium-potassium pump: If I am understanding correctly, every time this cycle occurs, an ATP is hydrolyzed in step 2 to produce a new ...
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Understanding the general dynamics of protein diffusion in cell plasma membrane

Background I am doing an undergraduate research project on the modelling and analysis of protein diffusion in plasma membranes. I am a physics and computer science student so naturally, I have many ...
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Examples of passive membrane transport proteins that only transport in one direction and their mechanism

I would like to know about those transporters with alternating-access-type mechanism, that can only efficiently shuttle molecules in one direction but the other direction is severely kinetically ...
symmetrickittens's user avatar
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Why does the concentration gradient of one ion represent the entire cell in the equilibrium potential of an ion? [closed]

The Nernst equation for the equilibrium potential of an ion(in this case potassium), $$E_{eq,K^+} = \frac{RT}{zF} \ln \frac{[K^+]_{o}}{[K^+]_{i}}$$ includes the ratio of the concentration of that ...
Sentient Rays's user avatar
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Are carrier proteins receptors?

I learnt about carrier proteins; how they bind a substrate/molecule, undergo a conformational change, and release the substrate/molecule on the other side of the membrane. We can take Glucose ...
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Why don’t animal cells fall apart when they are out of water?

Cell membranes are formed because of the phospholipid's shape and properties. The hydrophilic heads will arrange themselves to surround the hydrophobic tails, so the hydrophilic heads always face 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) ...
Gaurav Kumar's user avatar
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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. ...
pas-calc's user avatar
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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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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 ...
C-Consciousness's user avatar
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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" ...
ScienceDiscoverer's user avatar
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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 ...
BioPhysicist's user avatar
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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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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 ...
Nikhil Verma's user avatar
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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 ...
ceno980's user avatar
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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 ...
James's user avatar
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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 ...
Alex I's user avatar
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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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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 ...
ryry2000abc's user avatar
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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}^...
Jane's user avatar
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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 ...
Tom's user avatar
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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 ...
uhoh's user avatar
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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 ...
TheLast Cipher's user avatar
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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 ...
Treex's user avatar
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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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