Exchange of Gases, Nutrients and Waste

Discussion of all aspects of cellular structure, physiology and communication.

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Exchange of Gases, Nutrients and Waste

Post by barmy_army008 » Sun Jan 15, 2006 8:35 pm

Hi. I've been given a question which is to write brief notes on the exchange of gases, nutrients and waste products in both unicellular organisms and a 'two-layered coelenterate' (i'm not entirely sure what that is!).

I've found some information about gases in amoeba, and that its just simple diffusion, and i've also found some info on the surface area to volume ratio, but i'm struggling with the other stuff.

If anyone could help it would be much appreciated. Thank! :D

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Post by cool A-level student » Mon Jan 16, 2006 11:45 am

there are many kinds of transport :)
diffusion ya know so i wont talk bout dat

osmosis however is the movement of water from a high concentration to a low concentration (bear in mind all the water molecules are moving to and fro just more into the low concentration)

facilitated diffision is diffusion that happens via random movement fro a membrane but depends on the intrinsic carrier and channel proteins that transport substances through thier random movement to the other side, again this goes with the concentration gradient

active transport, err this is where it gets a little harder, a substance e.g. sodium connects to a carrier protein ready for transport but is going AGAINST the concentration gradient (i.e. from low to high) and so requires energy this is supplied via the substance ATP which connects with teh active site of the protein and alters the shape (SHAPE IS VERY IMPORTANT WORD HERE!) so that the sodium passes through, then the reacted ADP (product of ATP) disconnects and the protein is again ready

then we hve the complex names commin in :(
endocytosis and exocytosis
endocytosis is where the cell ingulfs materials from outside the cell and consumes it with the lysosomes (an organelle in which carriers nasty enzymes and eats stuff that isn't wanted or can be reused).
Exocytosis as you can imagine is the opposite where vesicles (small enclosed balls of membranes) connect with the plasma membrane and dump unwanted materials outside the cell, e.g. the cells that make up the saliva glands in your mouth are doing this to dump the enzyme outside the cell :)

thats wat i know on transportation of substances into and out of cells, if u hv any trouble understandin it then just mail me and ill get back to ya at some point ;)

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Post by Dr.Stein » Tue Jan 17, 2006 3:04 am

Well, it seems that all is covered... What should I do now?

Ahh, I will talk about two-layered coelenterates :) It means that their body wall consists of two layers or called as diploblastic, i.e. the endoderm (sometimes referred to as the gastrodermis) and the ectoderm or the epidermis. Between the two cell layers is the mesoglea, which ranges from little more than a glue to bind the both layers.

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Post by MrMistery » Tue Jan 17, 2006 6:59 pm

also we can say they are philum Cnidaria and that mesoglea contains neurons
"As a biologist, I firmly believe that when you're dead, you're dead. Except for what you live behind in history. That's the only afterlife" - J. Craig Venter

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