Questions tagged [cell-membrane]

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

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66 views

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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112 views

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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71 views

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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97 views

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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What are the characteristics of a cancerous cell surface membrane?

A notable characteristic of cancer is that it thrives at a high glycolytic rate, and doesn't require much aerobic respiration. I am curious, how does the cell surface membrane composition change so ...
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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 ...
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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 do most negatively charged phospholipids concentrate in the inner leaftlet?

Due to the asymmetry of the lipid membrane, negatively charged phospholipids such as phosphatidylserine, phosphatidylinositol are concentrated in the inner leaflet, creating a different charge ...
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Question on steroid hormones [duplicate]

I have learnt that there are 2 types of hormones: peptide hormones (hydrophilic, mostly bind to receptors on cell membrane) steroid hormones (hydrophobic, can pass through cell membrane and bind to ...
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106 views

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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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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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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39 views

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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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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185 views

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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544 views

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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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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What makes iodine an effective antiseptic?

I'm thinking about tincture of iodine, potassium iodide (Lugol's), and povidone-iodine (PVP-I) specifically, which, as is my understanding, work by solubilizing elemental iodine in an aqueous solution....
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What happens to embedded membrane proteins after a vesicle is formed?

When an animal cell is going through endocytosis it cell surrounds a food particle, and the membrane swallows it, creating a vesicle within the cell. However, what happens to the embedded ...
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How does lipoid pneumonia lead to acute respiratory distress syndrome (ARDS)?

How does lipoid pneumonia lead to acute respiratory distress syndrome (ARDS)? The vaping illnesses that have been happening on the news in the United States are being caused by the federal ...
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Why don't all my cell membranes "smush" when I fall?

I've read the question about cell membranes breaking apart, which is close to what I'm asking, though I'm trying to probe a bit deeper. I understand that there are hydrophobic forces keeping the cell ...
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Do carrier proteins constantly open and close or do they only work when a substance binds to them?

What causes carrier proteins to change shape ? Do they need energy to change shape? If that is true, how are they involved in Facilitated diffusion ? By changing shape, do we always mean opens from ...
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When is voltage generated across a membrane?

I'm very confused so bear with me please. Electrogenic pumps are carrier proteins that generate voltage through the movement of ions, right ? When is a voltage generated ? When there's a net ...
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Protein rafts over the Phospholipidic bi-layer

Does any of you know the specific name of the protein rafts that allow proteins to float over a double layer of phospholipids, (cell membrane)? I just feel there should be another name rather than ...
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same osmotic pressure of different solution

For example, There is a sugar solution with concentration $A_{1}$, how to determine the concentration of a NaCl solution which produce same osmotic pressure as the previous sugar solution toward ...
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How does the glycocalyx of cells attach together if they are negatively charged?

Context Thus, the entire outside surface of the cell has a loose carbohydrate coat called the glycocalyx. The carbohydrate moieties attached to the outer surface of the cell has several important ...
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Is plasma membrane permeable to sucrose

I searched a lot in the net but don't found a clear answer. I just want to know if plasma membrane is permeable to sucrose.

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