Questions tagged [cell-membrane]

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

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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 ...
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Can sperm cells penetrate the cell membrane of non-ovum cells?

Sperm cells have tiny bags of enzymes on their tip (the acrosome) which allow them to penetrate the ovum. My question is whether or not the process that allows sperm cells to penetrate the cell ...
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What's inside the perinuclear space?

The cell proper contains the cytoplasm in general and the cytosol in particular when referring to the fluid/gel without notable organelle. Once we move inside the nucleus there is the nucleoplasm and ...
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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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What change would you expect in phospholipid orientation of the membrane if the enviornment were mostly heptane?

The external and internal environment of the cell is basically water, thus phospholipids organize themselves the way they do (bilayer). If the environment were to magically become mostly heptane, how ...
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What's the ratio of saturated to unsaturated fatty acids in human cell membrane?

It's well established that the fluidity of a cell is largely dependent upon the ratio of saturated to unsaturated fatty acids that exist within the membrane, but, what exactly are the values for this ...
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308 views

Why don't surfactants destroy or incorporate into cell membranes?

How do surfactants remain on the surface of pneumocytes without (1) acting as a detergent or (2) the phospholipids getting incorporated into the membranes of pneumocytes... I'm guessing the answer ...
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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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Pharmacokinetics and cell-membrane permeability of Adenosine triphosphate disodium hydrate

【My Question】 (1) Please tell me the pharmacokinetics of this ATP (or Adenosine triphosphate disodium hydrate) when it is administered orally or intravenously. In particular, Does this material has ...
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What is the end-point of material from an apoptotic cell, after phagocytosis?

Apoptosis occurs. The organelles and interior material form apoptotic bodies that are packed in vesicles. The cell membrane breaks apart (cell no longer exists) and apoptotic bodies enter the ...
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Osmosis/ Facilitated diffusion

Water can move across the (Semipermeable non polar lipid) membrane by simple diffusion (osmosis). But polar molecules cannot pass through the non polar lipid bilayer, they require carrier proteins to ...
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52 views

What regulates cyclic AMP?

After reading a textbook chapter on GPCRs I am still confused by what regulates cAMP. I took in my notes that cAMP is made by adenylyl cyclase and destroyed by cAMP phosphodiesterases (also another ...
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70 views

Lipid Diffusion

Epithelial cells in the small intestine absorb lipids through simple diffusion but how does diffusion of lipids occur in the first place if they are insoluble in water? I thought that substances need ...
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139 views

What is the biological relevance of RIPPLE phase in membranes?

I was reading about ripple phase in bilayer lipid membranes which is described here as a meta-stable state between lamellar tilted crystalline and lamellar fluid state. It is also known that ripple ...
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What attaches plant cells to the cell wall?

In animal cells integrins span the plasma membrane and attach the cell membrane to the extracellular matrix. I was wondering how are plant cells attached to the cell wall? Is it just the middle ...
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Do GPCRs have 7TMHs?

I've screened a non-redundant set of GPCRs acquired from UniProt. I found a handful of examples of record IDs that contain more than the 7 TMHs. For example Q89609 and P20905, both of which have been ...
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Ion channels affected by gravity

In the literature I have found that action potentials behave differently when gravity is changed (cannot access fully). Action potential properties are gravity dependent. http://link.springer.com/...
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What are all of the currently known variations of the G zipper motif?

The G zipper motif is found in transmembrane proteins at an above random frequency and there are models explaining how it might help with multiple transmembrane intra-membrane helix bundle assembly. ...
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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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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 called the glycocalyx. The carbohydrate moieties attached to the outer surface of the cell has several important ...
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Are large cell bodies of neurons harder to depolarize than small cell bodies of neurons?

In order for the axon to initiate an action potential, we know that the axon initial segment must be brought to threshold. So my question is as follows: Say we have the minimum charge input, "X", ...
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What is the difference in the electrical excitability between a “large diameter soma” and a “large diameter axon”

There are two stereotyped statements that I have seen during my coursework regarding electric properties of neurons: Large diameter axons propagate action potentials more quickly than small diameter ...
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Reference request: Lipid composition in bacterial, yeast and human membranes

I would like to know about the lipid composition of different kinds of cellular membranes. I remember going through such a table once in a paper, but I am unable to find it anymore. What I am looking ...
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Transport in cell

Don’t the substances transported by the carrier protein against the concentration gradient diffuse through channel protein to again maintain the same concentration across the cell membrane? I mean , ...
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220 views

Why is ethanol osmotically active if it can enter through the plasma membrane easily?

This has been bugging me for a while, and I can't seem to find an answer to it, and I am sorry if I am asking a lot with this question(s). Firstly, I keep finding sources suggesting that ethanol is ...
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135 views

Why cells have a membrane potential?

What is the function of the membrane potential? Cells invest huge amounts of ATP to drive ion pumps to sustain this potential. Therefore it must have a very important function. I read somewhere that ...
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60 views

How to consider ions charges while calculating ions steady-state equilibrium concentration

i recently tried to find answer for following problem: "Assume that a membrane is permeable to Ca++ , K+ and Cl- but not to a large cation R+. The inside concentrations are [RCl] = 100mM and [...
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798 views

Is the signal peptide always cleaved during protein synthesis in the ER?

My university supervisor said that the signal sequence is always cleaved, however my text book differs. What I gather from my text book (though it isn't very clearly stated so i'm not sure) is that: ...
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How do (marine) cells not lose potassium?

Eukaryotic cells keep a sodium-potassium gradient across their external membrane. The concentration of potassium ions is about 5mM outside the cell. Although the potential gradient keeps most of these ...
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Effect of increasing Extracellular Na+ Concentration on resting voltage and likelihood of an action potential of occuring

If you increase the extracellular Na+ concentration how will this effect the resting voltage and likelihood that an action potential of will occur? Please explain using the Goldman–Hodgkin–Katz ...
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Mechanism of Octoxynol-10 as a preservative in vaccines

I noticed that the Fluarix Quad flu shot this season contains Octoxynol-10 rather than Thimerosal as a preservative. I am not expert in this area, so I did a Google search of "Octoxynol-10", and ...
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Differential Scanning Calorimetry for bacterial membranes

I would like to study the freezing and melting of bacterial membranes and would like to use Differential Scanning Calorimetry (DSC) to obtain the glass transition temperature of the membrane. However, ...
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Outlining cell edges of an epithelium

Is there any free software (for Windows, preferably) to detect cell edges in pictures of an epithelium, for example? I know Packing Analyzer does this, any other suggestions? Ideally, I would like ...
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Why do synergids lack cell wall on their chalazal end?

I've heard that synergids lack cell wall only on their chalazal end. Why is it so? Also, why does the egg (in an ovule) has its wall thicker towards the micropylar end?
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Why don't membrane-bound cells frequently collapse or spill their contents?

According to the fluid mosaic model, cells that are bound by a phospholipid bilayer membrane are divided from the environment by a rather thin boundary. Some compare the membrane to a soap bubble. If ...
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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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How are filopodia and membrane lengths related

I wonder how cell protrusions, in particular filopodia, form and how much of the cell membrane do they use. Is new membrane formed whenever a filopodium is created, or is the membrane simply deformed ...
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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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What is the difference between filopodia and lamellipodia?

I'm rather new to biology (I'm an applied mathematician) and I'm currently studying models of Notch-Delta dynamics between cells with filopodia and lamellipodia. What is exactly the difference ...
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Which proteins can lose adherence to cell surface by energical agitation?

According to this link https://www.cell.com/cell-reports/pdfExtended/S2211-1247(14)00121-1 CD44 protein lose adherence to cell surface by energical agitation Apart from CD44, which proteins can lose ...
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What is the electric field strength of microalgae?

Question: What is the electric field strength of microalgae? Background: So I have been having some problems with fungi contaminating my chromera velia algae cell cultures. I haven't determined what ...
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Why inhbition of RTK will not help in a case of mutant EGF?

I was given the following as an example for a quiz question but i don't understand the answer. Any help will be most welcome: Question: Iressa is a Tyrosine Kinase Inhibitor. As a young oncologe, ...
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Pelleting bacterial cells using centrifugation and getting proteins in the supernatant

Do significant amount of proteins from cells find their way in supernatant during pelleting? If the answer is yes then I see two ways in which protein can be in the supernatant . 1) Through lysis ...
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How does an increase in CO2 concentration affect Photosynthesis and Transpiration

I noticed a strange thing in my book. At one place it says that an increase in CO$_2$ concentration in the outside air decreases the rate of transpiration but at the other place it says that an ...
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Amount of Na+ needed to be transfered in order to depolarize the membrane?

I found out that the number of $Na^+$ ions that is needed to be transfered across the membrane to make it depolarized is a small number. In what way its proved? (Goldman equation maybe?)
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Does the SNAP-SNARE complex pertain only to exocytosis?

I'm learning the basics of cell biology and one thing about the SNAP-SNARE complex is confusing me a lot. I read that the SNAP-SNARE complex has nothing to do with endocytosis. But my question is: ...
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How osmotic pressure equals to turgor pressure in a fully turgid cell?

When a cell is fully turgid, its walls and membranes are completely stretched. At this time osmotic pressure of thecell will be equal to turgor pressure
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Number of phopholipid bilayer membrane an oxygen molecule diffused through

What is the minimum number of layers of phospholipids that a molecule of oxygen passes through when diffusing from the alveoli, through cells, to haemoglobin in the red blood cells? The answer to this ...