A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles. Biological membranes include cell membranes (outer coverings of cells or organelles that allow passage of certain constituents); nuclear membranes, which cover a cell nucleus; and tissue membranes, such as mucosae and serosae. Synthetic membranes are made by humans for use in laboratories and industry (such as chemical plants).
This concept of a membrane has been known since the eighteenth century but was used little outside of the laboratory until the end of World War II. Drinking water supplies in Europe had been compromised by the war and membrane filters were used to test for water safety. However, due to the lack of reliability, slow operation, reduced selectivity and elevated costs, membranes were not widely exploited. The first use of membranes on a large scale was with micro-filtration and ultra-filtration technologies. Since the 1980s, these separation processes, along with electrodialysis, are employed in large plants and, today, several experienced companies serve the market.The degree of selectivity of a membrane depends on the membrane pore size. Depending on the pore size, they can be classified as microfiltration (MF), ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) membranes. Membranes can also be of various thickness, with homogeneous or heterogeneous structure. Membranes can be neutral or charged, and particle transport can be active or passive. The latter can be facilitated by pressure, concentration, chemical or electrical gradients of the membrane process. Membranes can be generally classified into synthetic membranes and biological membranes.
Hello,
I am currently in the process of writing an Extended essay on the the "Effect of Tension on the fundamental Vibration of a circular Membrane" I have already completed the practical side of this by making 5 diaphragms with a 3 micron thick mylar membrane and have written up the methods...
Homework Statement
Calculate the membrane potential (Vm) of a cell, given the following resistances and equilibrium potentials (10 marks)
E(K) = -80mV, R(K) = 0.2*10^6 ohms, E(Na) = 60mV, R(Na) = 0.2*10^6 ohmsHomework Equations
Not sure
The Attempt at a Solution
In my texts I have read...
Homework Statement
I am trying to solve a circular membrane with clamped edges ans uniform pressure applied. I use large deflections.
Radius=0,1 m
Thickness=0,001 m
Pressure=100 Pa
E=10e6
poisson=0.3
Elements used=shell181
I attach a picture of the problem.
The Attempt at a...
I am interested in membrane recently.Can someone show the abc knowledge about membrane. I major in mechanics and I concern about the maths, physics and mechanics of membrane. Can somebody recommend some classic books and articles about this subject. Thanks.:rofl:
Hello,
I am working in the water treatment industry and for some of our tests we are using a bench scale 'high pressure' (8-10 bar) membrane filtration system. For the moment, the system comprises a tank from which water is pump into a membrane cell. A part of the flow just flows through the...
Hello,
I've a book in cell biology (it's an advanced book not a crash course or something) where's written that peripheral proteins are loosely connected to the membrane. However in most sources on the internet it's written that the protein is temporally adhered to the membrane.
I'm a bit...
Homework Statement
Please see question attached
Homework Equations
The Attempt at a Solution
Ok so I've been able to do the first few parts and have derived that Wm,n = c pi / L (m^2 + n^2)
I've thus been able to show that the second lowest freq is a factor of root(5/2)...
Hello everyone,
These are true,false questions. I'm on holiday so can't get help yet and this is not homework.
1.Increased permeability of the cell membraneto K+ than Na+ is important for maintaining resting membrane potential of cell?
Ok I know this is true but I don't understand...
Hi Guys,
I am new to this forum and would like to take this chance to say hello to everyone here.
Basically, my question is about the mechanical translation of cell membrane lipid peroxidation. I am wondering if lipid peroxidation has any impact on the stiffness of cell membrane. If so, is...
I have 2 questions related to the use of semipermeable membranes.
1) I'm using electrolysis to split water, but I'm wanting to separate out the hydrogen and store it separate from the oxygen for safety reasons. I'm wanting to use the hydrogen later for things such as fuel for my cookstove...
All I can really think to talk about is how the phospholipid bilayer (i.e. hydrophobic tails, hydrophilic heads) is structured, and how that only allows certains certain molecules in (blocks out polar molecules (except H2O), large molecules in general, ions etc.), while the others require forms...
Homework Statement
Consider a phospholipid bilayer membrane consisting of a mixture of 90% uncharged lipid and 10% singly charged acid lipid. Assume 68 Å^2 surface area per lipid head group, and assume further that the charged lipids are uniformly distributed and immobile. The membrance is...
Homework Statement
I am analyzing the deflection of clamped circle polysilicon membrane with radius=1500 um and thickness=1 um. The load is constant pressure ranging from 20 uPa to 20kPa.
The problem is that my analytical solution doesn't agree with the ANSYS solution.
Homework Equations...
Frequency of vibration for non-uniform membrane -- Partial Differential Equations
Hi guys, I'm having a lot of trouble with a conceptual problem in my PDE's homework. I don't think the answer involves a lot of work, I think I'm just not understanding something...
Homework Statement
Consider...
Hello everyone,
What is the function of the mucous membrane of the mouth. Ok if it is to trap infectious agents and keep everything moist, where does mucous drain to after it traps the pathogens. Do they fall down from the mouth. Also since the first thing that comes to mind when mucous pops...
Hello. I want to start off with a simple into. I have not been to any of the classes you have. I can not go to the classes you have. and I find it odd, that when I can I strive to understand the things you all talk about. but the equations and formula's you use are Greek to me. so please, keep...
I often read on books that linear triangles do not have membrane locking for large deformations of plates/shells. I completely don't understand how this is possible. If one uses the well-known CST, stretching is measured as the increase in length of each edge of the triangle. Then, in the limit...
Homework Statement
Homework Equations
What is the boundary condition for a free edge of a rectangular vibrating membrane? (not plate)
The Attempt at a Solution
Hi, I'm looking for information on blood and neuron cells. Specifically I need to know how the membrane transport mechanism in blood and neuron cells work? I am aware of concepts such as active diffusion, facilitated diffusion, and simple diffusion.
The task is to look at the membrane...
Homework Statement
Cell Membranes and Dielectrics Many cells in the body have a cell membrane whose inner and outer surfaces carry opposite charges, just like the plates of a parallel-plate capacitor. Suppose a typical cell membrane has a thickness of 8.0×10−9 , and its inner and outer...
This isn't homework - just working through questions in my text. The question gives two concentrations of calcium ions inside and outside the membrane and asks to find the Nernst potential - ok no problem there.
Then it asks if the calcium ions are in equilibrium if the resting potential is...
Hi all -
I have a problem that I'm probably going to model in COMSOL and would love to hear some ideas on how to get the proper BCs.
Attached is the picture from Truskey. Essentially, the problem consists of removing waste (water) from the membrane tube at a rate of ~ 1 mL/min with a pressure...
Homework Statement
Explain why carohydrates are found attached to integral membrane proteins on the outside, but almost never on the inside (cytoplasmic face) of cell membranes.
Homework Equations
-----------The Attempt at a Solution
Carbohydrates bond with integral membrane proteins on the...
Homework Statement
Describe the methods by which proteins are clustered in the plasma membrane.
Homework Equations
There are none really; it's theory.
The Attempt at a Solution
I understand that the proteins bond with the cytoskeleton (actin microfillaments and intermediate...
What does the absorption rate of body tissues depend on? For example, at what rates would the rectum, vagina, mouth, and skin be able to absorb a certain chemical? Does it depend on the size of the molecule? If it is water-soluble does that make it easier to absorb? In fact, what makes something...
Hi all,
Is there any relation between the membrane capacitance and the Nernst potential?
Refs:
membrance capacitance
http://www.cnbc.cmu.edu/~bard/passive2/node5.html
Nernst potential
http://en.wikipedia.org/wiki/Nernst_equation#Nernst_potential
Homework Statement
A pump is electrogenic, meaning that 3 Na ions are pumped in for 2 K ions that pumps out. Given that the active current --> I' (Na) 30 E-9 , find the passive current of Na --> I (Na). Assume cell is in steady state so Vm, [Na] inside and [K] inside is constant...
hi
i was wondering if you could help me answering this question please ..
"compare between forces that involved in the K+ channel during resting membrane potential and hyperpolrization" ?
I'm sorry but i need to know the answer ASAP ..
:biggrin:
Hello all.
I just had a few conceptual problems if someone wouldn't mind explaining to me.
When looking at a simple cell membrane, potassium ions tend to move out of the cell along their concentration gradient until its electrical gradient is strong enough to counterbalance it, thus...
Hello,
I'm having a lot of trouble understanding/visualizing the movement of ions through a capacitor. My book says the total current flowing through a neural membrane (that is in steady state) is equal to the current flowing through ion channels (rm) and the capacitor. However, how can ions...
Homework Statement
diffusion thru a semipermeable membrane.
Homework Equations
section 1 of the lab
LAB - dialysis tubing containing distilled water and the beaker containing glucose and starch .. put it in water.
Leave it over night and jot the changes, it goes through osmosis but...
VERY URGENT: Please help with Diffusion Question and Membrane Protein question
Proteins associated with the plasma membrane can be classified as either integral membrane proteins or peripheral membrane proteins. For the following types of proteins, please specify whether they would be integral...
according to wikipedia:
Myelin increases resistance across the cell membrane by a factor of 5,000 and decreases capacitance by a factor of 50.[citation needed]
why would it decrease capacitance? I thought dielectrics were added between capacitor plates to increase capacitance...
Homework Statement
Which of the following is NOT important in determining a neurons membrane potential:
The function of the neuron or the location of the neuron?
Homework Equations
N/a
The Attempt at a Solution
The function of a neuron is obviously the integration, summation, and...
For those of you that arent very familiar with PEM fuel cells, their shortcomings basically revolve around the carbon/platinum membrane and is essentially the "heart" of the fuel cell. But why does a fuel cell need a membrane to function? If you think about it, just about all energy conversion...
Homework Statement
Cell membranes (the walled enclosure around a cell) are typically about 7.5 nm thick. They are partially permeable to allow charged material to pass in and out, as needed. Equal but opposite charge densities build up on the inside and outside faces of such a membrane, and...
Homework Statement
he fluid within a living cell is rich in potassium chloride, while the fluid outside it predominantly contains sodium chloride. The membrane of a resting cell is far more permeable to ions of potassium than sodium, and so there is a transport out of positive ions, leaving...
Hi all, sorry if this has been asked before but i can't find a thread with the info I'm after. I'm doing an access course at lvl3 (AS/A2) which includes biology and I'm stuck on the following question as part of an assignment I'm to hand in next week.
Q: Suggest an explanation for the fact...
Dear Sir,
This is Thangamani, doing research on sensor design. I have gone through Mr. Robert Dean (RF CMOS Designer, MEMS Optical, Inc) article that available on internet ( if not mistaken its from MEMS forum) discussed analytical solution about rectangular membrane. Since i am...
Homework Statement
a biological cell is immersed in a 50mM solution of NaCl at 37C. the cell's membrane is permeable only to Na+ ions. When the system reaches equilibrium, a potential diff of 54.9mV is measured between the inside and the outside of the cell where the inside has the higher(...
I have some questions that i am not sure...can u guys help me out ?
1. Which of the following is the best phrase to describe the modern view of membrane
structure?
a. Membranes are lipid-lipid bilayers.
b. Membranes are lipid-lipid bilayers with associated proteins.
c. Membranes are...
I had this lab done where we took beets and tested the effects of pH on membrane permeability.
We used different concentrations of HCl and NaOH. Why did I get such a strong colour intensity with a test tube that had 0.001 M NaOH? And how do I know this experiment affected the protein...
This question is the last thing that is bugging me about my basic understanding of a nerve impulse:
How can the there be a non-zero voltage across a membrane if the solutions on either side are electrically neutral? It seems like the existence of a gradient should necessitate at least one...
The inner and outer surfaces of a cell membrane carry a negative and positive charge, respectively. Because of these charges, a potential difference of about 0.0730 V exists across the membrane. The thickness of the membrane is 8.22E-9 m. What is the magnitude of the electric field in the...
[Chemistry] Another electrochemistry question
Homework Statement
Given the following half-reactions:
Ce4+ + e− → Ce3+ E° = 1.72 V
Fe3+ + e− → Fe2+ E° = 0.771 V
A solution is prepared by mixing 7.0 mL of 0.30 M Fe2+ with 8.0 mL of 0.12 M Ce4+.
Calculate [Ce4+] in the...