Questions tagged [cell-membrane]

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

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Membrane Potential Question

Hello, I've come across this question and am slightly confused. The question states that for this scenario the membrane is only permeable to K+, thus would the membrane potential in this state just be ...
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Which chemical components make up cytoplasm?

I am writing a thesis on foraminifera in order to understand these organisms properly, I want to understand the cytoplasm as well as the shells (tests). Unfortunately, I cannot find any literature ...
4 votes
1 answer
164 views

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 ...
11 votes
2 answers
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At what point during an action potential are the sodium potassium pumps working?

I'm trying to understand how all of the potentials during an action potential are created. My question specifically is about the sodium potassium pumps, however I would also be grateful if someone ...
6 votes
3 answers
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Why do cell membranes let small non-polar molecules through but won't let small polar molecules through?

If the hydrophobic hydrocarbon chain of the phospholipid prevents the movement of polar molecules through the membrane. Why does the hydrophilic phosphate head of the phospholipid not prevent the ...
2 votes
1 answer
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Chloride Clamp and Nernst potential

The Nernst potential for chloride is -70 mV. The neuronal Resting Membrane Potential (RMP) is -70 mV. Under this condition, if the chloride channels are open (as it happens in Inhibitory Post Synaptic ...
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1 answer
125 views

Why don't membrane potentials violate the principle of electroneutrality?

The principle of electroneutrality states that the number of anions and cations in a solution must be the same, i.e., that there will be no charge excess in any side of the membrane separating two ...
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1 answer
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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 ...
3 votes
2 answers
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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 ...
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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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1 answer
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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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1 answer
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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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2 answers
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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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1 answer
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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 ...
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1 answer
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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 prohibition ...
9 votes
3 answers
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Why don't phospholipid bilayers dissolve?

I just started learning about the structure and composition of cell's membrane and there is something that I fail to understand. The membrane is composed of a phospholipid bilayer. The phospholipid ...
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1 answer
104 views

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 ...
3 votes
2 answers
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What are multicell spheroids?

I'm from a maths background and I'm doing some research on mathematical models of cancer. I've come across a lot of literature mentioning "multicell spheroids" in the context of avascular ...
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1 answer
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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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2 answers
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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 ...
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1 answer
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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 ...
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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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1 answer
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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 ...
2 votes
1 answer
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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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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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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. ...
2 votes
1 answer
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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 ...
7 votes
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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 ...
3 votes
1 answer
260 views

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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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?
4 votes
1 answer
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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 ...
1 vote
1 answer
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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 ...
6 votes
1 answer
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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 ...
9 votes
0 answers
260 views

What are the secondary structure requirements for cell-penetrating peptides AKA protein transduction domains

Cell penetrating peptides. Cell penetrating peptides (CPPs) are a class of short amino acid sequences which are sufficient for crossing cell membranes and delivering themselves along with any attached ...
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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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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 ...
1 vote
1 answer
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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 ...
9 votes
1 answer
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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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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 ...
-1 votes
1 answer
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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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1 answer
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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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1 answer
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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 ...
2 votes
1 answer
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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 ...
1 vote
1 answer
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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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