Cells Questions?

Question

Hypothesize why the pores in the cell membrane are different sizes?

Do you think cells could survive without diffusion? Explain why or why not.

Diffusion = the movement of molecules from an area of high concentration on an area of lower concentration

Answer 1

cells can't survive without diffusion. that is scientific fact! Without being able to diffuse you will end up with waste products inside the cell which will eventually kill the cell. Also as more waste grows if you can't get rid of it you also risk the cell lysing (bursting). Another way to look at it is water content. The cell needs enough water in the cell for functional purposes but also needs an equal amoung outside to prevent becoming withered up or bursting depending on where concentration is greater.

The pores are different sizes because different molecules need to diffuse or use active or passive transport to get through them. Basically it is like a key hole and each molecule is a different key. You have to have enough key holes for each type to enter and exit. Sometimes you can have a key hole that fits multiple keys but many times that is not the case.

Answer 2

1. What country were you born in? USA 2. What country do you live in now? USA 3. What country have you never been to, but would like to visit one day? UHHHHHHH. I've been almost everywhere. Switzerland? 4. If you couldn't live in the country you were born in or where you currently live...where would you go? Australia. I've already lived there for 2 years and i loved it. 5. What are all the countries that you have been to? Amsterdam, Italy, France, England, USA, Canada, Mexico, New Zealand, Australia. 6. If you could have "marry" a guy/girl from any country, which country would you choose? Italy or Australia 7. What country would you want to be born in if you couldn't have been born in the country that you were born in? Australia 8. What country has the best flag out of the ones that you know of? Japan. 9. What country has the best accent? Australia. ***At what age did you get your first cell phone? 11.

Answer 3

Well it depends because for diffusion, if the cell is in a hypotonic solution, that can actually kill the cell and caused it to be lysed if it's an animal cell. For plant cells, they prefer to be in hypotonic solutions b/c it makes them turgid.

My opinion personally is that. . .no, cells would not be able to survive without diffusion b/c the nutrients/other substances needed would not be present.

I'm not sure if I'm right though. Good luck with that!

Answer 4

The pores are different sizes to allow or not allow different protiens into the cell. They could not survive without diffusion. Diffusion is needed to balance their environment and the intake and excreation of proteins. ie, food and wastes

Answer 5

The membrane itself does not have "pores". The lipid bilayer is almost impermeable to water, small molecules, and macromolecules like protein or nucleic acid.

Substances get through the membrane using "transport" proteins that are imbedded in the lipid of the membrane. These transporters completely span the width of the bilayer.

The so-called "pores" are actually channels or pathways within the core of the transport protein. There's not actually a "pore" or hole straight through in most cases, because the substance crossing the membrane through the transport protein must interact with amino acids inside the pore as it crosses. Most pores or channels are not at all straight. Instead of thinking about a straight straw poked through the lipid of the membrane, think of one of those flexible straws winding a twisting pathway across the membrane.

The transport proteins discriminate between different substances like different ions because of the 3-dimensional (spatial) arrangement of the amino acids lining the "pore". Sometimes it's as simple as the amino acids forming a small constriction in the tube (like tying string around the straw and pulling it tight but not all the way). Only substances of a certain size can pass through the hole that's left. Most of the time however the selectivity of any particular transport protein is a complex mixture of the complete 3-dimensional pathway through the channel or pore, charge or lack of charge on the amino acids lining it, hydrophobic (water hating) or hydrophilic (water loving) amino acids, aromatic amino acids (those amino acids with benzene or indole rings), and many other factors.

Transport proteins are very selective. Most can transport only one thing or at most only a very few closely related things. There are a couple of exceptions to this, but very, very few. Since they are so selective generally, your cells have to have a lot of different transport proteins in their membrane. A bacterium like Escherichia coli has about 4600 total genes on its chromosome. About 10% (or around 500) of these genes probably encode a transport protein. The proportion is slightly less in mammalian/human cells. We have perhaps 60-80,000 genes and perhaps 4-5,000 transport proteins. Not all are expressed in any particular cell of course, but each cell has probably several hundred types of transporter.

The following websites may also help.
(You'll have to download some plugins for IE or Netscape for some of these, but they install automatically and the links are on the pages.) http://www.scripps.edu/mem/biochem/CI/
http://arc-gen1.life.uiuc.edu/Bioph354/membrane_phase.html
< http://www.accessexcellence.org/
http:// www.biology.arizona.edu/cell_bio/tutorials/membranes/main.html



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Answer 6

no