Beginning of a cell - (Mar/03/2007 )
Hi there
The other day in class we talked about cell birth and stem cells--and I am soo confused..is the following correct?
I don't understand (and I'm talking about any eukaryote)-we begin as a zygote right?..and then form there on in we keep dividing and dividing till what?...we get to a eight cell stage? (or does it keep on dividing till 70 or so cell stage-as I read that somewhere)...and then its called a blastocyst right?..and those cells within are the basis of all the cells we will form..eg: heart, muscle, neurons, liver etc etc...and those 70 or so cells are called stem cells right?..so now at this point these the majority of these cells are designated a particular path eg to the heart, liver etc etc..and this all occurs by mitosis???...I have looked on line to find good animations that will make me understand but have failed...I know I'm probably asking really stupid questions but I just wanna know so I can carry on the rest of the year in peace... ...but then my textbook goes on to talk about symmetric/asymmetics cell division..is this just basically talking about eg a heart stem cell forming other heart cell stems (to keep that stem cell population maintained) and it also forms a restrictied-potential stem cell which goes on to form the "real" heart cell-the termianlly differentiated stem cell--but then why even bother to make another heart stem cell-cos isn't it correct to say once some of the heart cells die then they cant be formed again?...eeeek is this right?...
Also just a quick word on immunofluorescence microscopy..just wondering when it says this technique is used to localise specific proteins and then it goes on to lets say myosin it says the flurochrome/antibody will bind to the corresponding antigen..umm what I dont get is antigens are foreign substances right? well where do these antigens come from in the first place that allows us to bind the antibody..
Sorry if it sounds dumb
Thanks
biology_06er
An antigen need not be a foreign substance ( though it usually is). Like in case of auto immune diseases.
But for immunofluorescence, the antibodies are developed to a particular antigen, which is a part of a specific protein. Now if the antigen is present,and the antibody is applied, it binds to it and applying a secondary antibody with a fluorophore gives you a fluoroscence. The antibodies are made in different animals against specific antigen and then used on tissue to detect the specific antigen (part of a protein). I hope this explains.
No question is ever dumb !!!! and no student is dumb, its the teachers who are stupid that they are unable to pass knowledge to the students. 
About the first question, If I understood it correct.
During development, our body makes more cells than necessary and then as part of the development, the unwanted cells die. Its like how a sculptor starts from a big block of stone and then slowly chips away the unwanted parts and give it a finishing touches in all places.
Hey there!!
Thanks for the reply!
could you please tell me why we have to add a secondary antibody (is it there because without it the fluorochrome won't work)...and how is it relevant to the first antibody?...we did this in our lab the other day but did it cos it said to-(but didn't actually know what the point of it is) but now that I'm going over that lecture in the textbook it just talks about one antibody--doesnt't say anything about a secondary antibody...
also with that cell question--so we do actually reach a stage where we are boaut 70 cells "big" right?.. and do you mean from those 70 cells those that we don't want/need some die..?..so the ones we are left with become the "stem cells" from which all our other cells arise from via mitosis ??
Thanks-much appreciated
biology_06er
Thanks for the reply!
could you please tell me why we have to add a secondary antibody (is it there because without it the fluorochrome won't work)...and how is it relevant to the first antibody?...we did this in our lab the other day but did it cos it said to-(but didn't actually know what the point of it is) but now that I'm going over that lecture in the textbook it just talks about one antibody--doesnt't say anything about a secondary antibody...
Secondary antibodies in immunodetection is something of a man made situation. (basically to save cost and to simplify immuno detection techniques).
So take the situatation:
your antigen specific antibody is bound to the protein you want to see. Ok, now what? The antibody is bound but can anyone see an antibody? nope, nobody can see antibodies. they are just too small. Now the trick to immuno detection techniques is to stick a molecule that glows.( fluorochrome ) to the antibody. So sit in dark, shine a UV light on it (which humans can't see) and watch the antibody light up.
okay. now there are a million different proteins different people want to look at. And as you can imagine sticking a fluorochrome onto an antibody is not easy and expensive. (purification, processing loses, damage due to chemical modification, loses to repurification) And making specific antibodies is difficult. Mainly because there is only ever a few people who want that specific antibody. So going through all that trouble to optimise conditions is not very profitable.
So using a single antigent specific antibody that has a fluorochrome attached is not profitable.
But what if you had 2 antibodies. The first being antigen specific (the expensive one). And a second antibody made to recognise and bind to the first. And there are slight difference in antibody structure between sepecies. So lets have a system. In my company all antigen specific antibies are made using rabbit antibodies. And we will make a secondary antibody from goat that will recognise rabbit antibodies. This goat antibody I will chemically manipulate to attach a fluorochrome. And I can make alot of these secondary antibodies because everybody who buys antigen specific antibodies will use this secondary antibody. And if this standard becomes the standard for several companies, well all the better. I have economy of scale to mass produce a single chemically manipulated antibody. (and thus able to withstand processing loses)
Thus you have the story in a nut shell. We employ glowing secondary antibodies because it is cheaper to do it this way. Not because it is an elegant system, or easier for the user.
Thanks-much appreciated
biology_06er
No. Scolix explination of cell death occurs on a much wider and more general scale. Consider your fingers. We have them because all the cells between the fingers have died. We all started off with a paddle. which thins to webbing. And the webbing finnaly dissapears leaving individual digit. Or eyelids. Or the circuitry in the brain. Many example. Controlled cell death doesn't just occur during development, it occur well after birth.
As for blastocyst question.. i think you have several ideas muddled up.
Firstly there are many ways to skin a cat. And nature has tried about every single way.
There is cell fate dependent and cell location dependent differentiation.
In some phyla, every single cell has a plan, a fate already set for them. Said cell will become so and so. Their fate was set before the cell even divided. Each cell is special. Kill one cell and a whole section of the animal goes missing.
In other phyla, cell fate purely is based on where the cell is at a moment in time. Contact and communication with neighbouring cells tell the cell what it should become. No cell is important. Kill one cell and some other cell takes its place. Cut the blastocytes in half and you get twins. (we, mammals belong here) (Well to a point at the blastocyst stage there already are 2 types of cells ,the inner cell mass (which becomes the embryo proper, and the trophoblast which becomes the placenta) The inner cell mass is at this stage in time are totipotent. They can become any type of cell. Their fate has been only decided so far as that they will become part of the embryo.
And in other phyla you get a mix. cell fate on one axis (vertical )and cell location on another axis (horrizontal).
As for your other question, I think you will have to consider this. How similar does a heart cell look like neuron or a epithelial cells or a secretory cell. The answer is not much to very little. Each cell type is highly specialised.
So think of it this way, you want to create a society you need policemen, teachers, soldier, doctors, firemen, garbage men, scientist, postmen, fighter pilots, lawyer etc. All these people start out as school student. However converting a school student to any of these professional takes training, more training then a single course or school can offer. And some professions may share some skills.
So a cell does something akin to what we do. We set up instituitions of learning and traning that get ever more specilised the person reaches her/his ultimate profession. So a totipotent cell makes puripotent cells, which goes on to make every more spealised cells, and so forth up the chain. Also remember you do start with less then 70 -100 cell and all these totipotent cells have to make an animal composed of billions of cells. So you need a bit of an amplification process.
Thanks man!...that was a awesome explanation!!! yay!!
one other question I have-about membrane transport-in another of our classes we are learning membrane transport..so just wondering if a cell burts/shrinks its due to either the extra on inter/celluar fluid being out of balance right?...well if this is the case is the reason for it being out of balance that certain transport proteins are not working? and if this is the case eg: in the intestine, say one of the cells isn't working then its fine right---does the problem lie in the fact many many cells in the intestine have membrane transport problems?
Hope this makes sense
biology_06er
and thanks again perneseblue 
Thanks for the reply!
could you please tell me why we have to add a secondary antibody (is it there because without it the fluorochrome won't work)...and how is it relevant to the first antibody?...we did this in our lab the other day but did it cos it said to-(but didn't actually know what the point of it is) but now that I'm going over that lecture in the textbook it just talks about one antibody--doesnt't say anything about a secondary antibody...
Secondary antibodies in immunodetection is something of a man made situation. (basically to save cost and to simplify immuno detection techniques).
So take the situatation:
your antigen specific antibody is bound to the protein you want to see. Ok, now what? The antibody is bound but can anyone see an antibody? nope, nobody can see antibodies. they are just too small. Now the trick to immuno detection techniques is to stick a molecule that glows.( fluorochrome ) to the antibody. So sit in dark, shine a UV light on it (which humans can't see) and watch the antibody light up.
okay. now there are a million different proteins different people want to look at. And as you can imagine sticking a fluorochrome onto an antibody is not easy and expensive. (purification, processing loses, damage due to chemical modification, loses to repurification) And making specific antibodies is difficult. Mainly because there is only ever a few people who want that specific antibody. So going through all that trouble to optimise conditions is not very profitable.
So using a single antigent specific antibody that has a fluorochrome attached is not profitable.
But what if you had 2 antibodies. The first being antigen specific (the expensive one). And a second antibody made to recognise and bind to the first. And there are slight difference in antibody structure between sepecies. So lets have a system. In my company all antigen specific antibies are made using rabbit antibodies. And we will make a secondary antibody from goat that will recognise rabbit antibodies. This goat antibody I will chemically manipulate to attach a fluorochrome. And I can make alot of these secondary antibodies because everybody who buys antigen specific antibodies will use this secondary antibody. And if this standard becomes the standard for several companies, well all the better. I have economy of scale to mass produce a single chemically manipulated antibody. (and thus able to withstand processing loses)
Thus you have the story in a nut shell. We employ glowing secondary antibodies because it is cheaper to do it this way. Not because it is an elegant system, or easier for the user.
Thanks-much appreciated
biology_06er
No. Scolix explination of cell death occurs on a much wider and more general scale. Consider your fingers. We have them because all the cells between the fingers have died. We all started off with a paddle. which thins to webbing. And the webbing finnaly dissapears leaving individual digit. Or eyelids. Or the circuitry in the brain. Many example. Controlled cell death doesn't just occur during development, it occur well after birth.
As for blastocyst question.. i think you have several ideas muddled up.
Firstly there are many ways to skin a cat. And nature has tried about every single way.
There is cell fate dependent and cell location dependent differentiation.
In some phyla, every single cell has a plan, a fate already set for them. Said cell will become so and so. Their fate was set before the cell even divided. Each cell is special. Kill one cell and a whole section of the animal goes missing.
In other phyla, cell fate purely is based on where the cell is at a moment in time. Contact and communication with neighbouring cells tell the cell what it should become. No cell is important. Kill one cell and some other cell takes its place. Cut the blastocytes in half and you get twins. (we, mammals belong here) (Well to a point at the blastocyst stage there already are 2 types of cells ,the inner cell mass (which becomes the embryo proper, and the trophoblast which becomes the placenta) The inner cell mass is at this stage in time are totipotent. They can become any type of cell. Their fate has been only decided so far as that they will become part of the embryo.
And in other phyla you get a mix. cell fate on one axis (vertical )and cell location on another axis (horrizontal).
As for your other question, I think you will have to consider this. How similar does a heart cell look like neuron or a epithelial cells or a secretory cell. The answer is not much to very little. Each cell type is highly specialised.
So think of it this way, you want to create a society you need policemen, teachers, soldier, doctors, firemen, garbage men, scientist, postmen, fighter pilots, lawyer etc. All these people start out as school student. However converting a school student to any of these professional takes training, more training then a single course or school can offer. And some professions may share some skills.
So a cell does something akin to what we do. We set up instituitions of learning and traning that get ever more specilised the person reaches her/his ultimate profession. So a totipotent cell makes puripotent cells, which goes on to make every more spealised cells, and so forth up the chain. Also remember you do start with less then 70 -100 cell and all these totipotent cells have to make an animal composed of billions of cells. So you need a bit of an amplification process.
Hello there, I really appreciate the answer - not every one can do it. Nice way of answering - good analogy too.
Hey there scifi
kinda freaky--but on another website I use to use at high school my username was scifi...so was like !!!!!! when I saw your name hahaha
one other question I have-about membrane transport-in another of our classes we are learning membrane transport..so just wondering if a cell burts/shrinks its due to either the extra on inter/celluar fluid being out of balance right?...well if this is the case is the reason for it being out of balance that certain transport proteins are not working? and if this is the case eg: in the intestine, say one of the cells isn't working then its fine right---does the problem lie in the fact many many cells in the intestine have membrane transport problems?
Hope this makes sense
biology_06er
and thanks again perneseblue
Cells shrinking or bursting is more likely to be due to the osmotic environment. If a cell goes into distilled water, what direction will osmosis operate? Low salt conc to high salt conc, therefore into the cell. If the cell membrane can no longer stretch, POP goes the cell. There may be something happening with transport proteins moving ions into and out of the cell, but osmosis is way more likely to do damage.
Problems in the intestine are more likely due to transport protein problems. Pernicious anaemia, for example, happens because the body cannot transport iron out of the gut. Same story with other absorption diseases.
all of a sudden i feel guilty for giving one line answers.