Membrane Definition and 148 Threads

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...

What is the membrane theory?

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...

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...

is our universe a membrane with almost no dimension(the space between two quarks)?

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...

Is it possible to create an artifical selectively permeable membrane? I need one for a science fair project idea I had.

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...

Is there any kind of semipermeable membrane which would diffuse gas but wouldn't let liquid to pass. If yes what would that be? Thanks, Vladimir.

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...

if the Plasma membrane is amphipathic (hydrophobic and hydrophilic), why does it only allow hydrophobic stuff to pass thru?

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...

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...

im meant to design an experiment (at AS level) and perform it to see how the pH can affect beetroot cell membrane permeability. i don't know where to start. anyone have any experiments?? thanks :biggrin:

I am currently looking into membrane biophysics as an area of research, and I will start doing some undergraduate research with one of my professors in his biophysic's labs. But I am curious how is the theory end of Biophysics looking, particularly for graduate programs. I have bumped into a...

Why exactly does the cell membrane become more fluid in higher temperatures than lower? Does it have anything to do with the degree of saturation?

You are accostumating me bad. I never find good sites for what I am looking for and you always find. This time I am looking for the various theories about the structure of the cell membrane till the fluid mosaic. Thank you one more time. :biggrin:

Hello there; In class we learn that "cholesterol increases membrane fluidity at low temperatures, and decreases membrane fluidity at high temperatures." I can see how it would increase fluidity at low temperatures since it attachs to the lipid tails of the membrane, which would push them...

hi, this is the last question I'm having trouble with.. the question is: Fine sand is sprinkled on the horizontal membrane, which vibrates in the vertical direction with frequency f = 500 Hz. The sand particulates bounce at the height of 3 mm over the level of the position of equilibrium of...

This is about membrane potentials in a nerve membrane. I've already studied the Nernst equation and the Goldmann equation, but I have found its significance in explaining the resting potential. The Nernstian potential occurs at equlibrium, when concentration gradient = opposing electric...

I have this question I need to answer and I am confused. I've checked my notes and book and can't find an answer. Here is the question: "Even though the beta barrel configuration for a transmembrane protein channel would seem an ideal channel, most of the channel proteins have multipass alpha...

cell membrane---please help me...--- [FONT=Verdana] :confused: What kind of molecules make up the majority of the cell's membrane? :confused: Can anyone help me?

The membrane of a cell is electrically equivalent to a parallel plate capacitor. A typical cell has a spherical shape with a radius 10 μm and it has a potential of −60 mV with respect to outside. The thickness of the membrane is about 0.01 μm, and it has a dielectric constant of 2. Find: (a)...

hi, my textbook shows how cholesterol sort of patches the cell membrane together, keeps it at optimal fluidity... I was just wondering how cholesterol is able to do this... I am in grade 11 biology I am not being tested on this or whatever I was just wondering if anyone knew...

there are 2 probs here. 1) 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 0.0680 V exists across the membrane. The thickness of the membrane is 7.95×10-9 m. What is the magnitude of...

Suppose you have a tube made of nylon. It is filled with air. Obviously, the cross-section is a circle. Now, suppose that on the top and bottom of the tube, a length of rigid sheet metal is attached and does not permit curvature, so that the cross-section after inflation looks like this...

http://www.google.ca/search?q=cache:0j8NdYaQ3L4J:www.foodsafetynetwork.ca/biotechres/activityextraction.pdf+Kiwi+DNA+Extraction+Lab&hl=en The above url is a lab that states that to do a DNA extraction of kiwi the cell membrane is eliminated through liquid detergent and mechincal mashing -...

i learned in my cellular biology class today that hydrophillic molecules don't diffuse through the membrane easily, since the inside of the membrane is hydrophobic. my question is that water easily diffuses through the cell membrane, and water isn't just hydrophillic, it is hydro! so why can...

Greetings. According to my textbook (again, this might not be really accurate because of translation): Now, here is my question : If proteins are just molecules (big ones i guess), how do they 'know' what the cell needs at a certain time (to let it into the cell) ? Thanks in advance.

I have noticed while looking at my cat that there is a secondary membrane (first beign the mucus membrane covering his eye it is a little har do expsplain so if you have a cat pick it up and look at it's eye you will notice a white area beteen his outside eye and the side of it's nose. It it...