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Cell wall and uptake of nutrients

by Monique
Tags: cell, nutrients, uptake, wall
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Monique
#1
Feb14-04, 07:56 AM
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A cell wall is a rigid structure, so I wonder how organisms with such a structure are able to take up nutrients from their environment?

If there is only a plasma membrane, vesicles can be formed which pinch off and thus take up nutrients from the environment and merge with other vesicles to form endosomes and later lysosomes. The other way transport is also possible, where waste products can be released by merging of a vesicle w/ the plasma membrane.

So what happens in plants or fungi?
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Jikx
#2
Feb20-04, 07:05 AM
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I'm interested in this as well...

the only closest thing i could find was

the subsequent uptake of nutrients by the plant roots, the myriad of steps involved in translocation to the vasculature (release by exporters from one cell, uptake by the next cell, transfer between vascular systems etc.)
which makes little sense to me.
rockind78
#3
Feb20-04, 01:11 PM
P: 78
I just asked this question in my Mycology class. Fungal walls are either (usually) composed of chitin or cross-links of N-Acetylglucosamine. Either way, they don't seem to pose a problem for nutrient uptake as they go right through the cell wall. I think the primary purpose of the cell wall is to provide structure.

Monique
#4
Feb20-04, 01:16 PM
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Cell wall and uptake of nutrients

Yes, but how are nutrients taken up by the cell? The cell 'drinks' its environment by forming vesicles which internalize by pinching, which are then routed to the lysosomes for digestion.

Are you saying that although there is a cell wall, the plasma membrane still forms these structures? Isn't the cell wall connected to the plasma membrane?
Monique
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Feb20-04, 01:28 PM
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Just to give a concrete example of the process I am talking about: LDL uptake of the cell.

LDL in the circulating blood binds to LDL receptors on the plasma membrane at the extracellular space, a clatherin coated pit forms on the cytosolic side through adapters on the receptor. The material is endocytosed, the LDL is routed from the endosomes to the lysosomes and the receptors get recycled to the plasma membrane.

Ah, I just lookes the following up in my textbook.. the process is called pinocytosis:

Virtually all eucaryotic cells continually ingest bits of their plasma membrane in the form of small pinocytic (endocytic) vesicles, which are later returned to the cell surface. The rate at which plasma membrane is internalized in this process of pinocytosis varies between cell types, but it is usually surpisingly large. A macrophage, for example, ingests 25% of its own volume of fluid each hour. This means that it must ingest 3% of its plasma membrane each minute, or 100% in about half on hour. Fibroblasts endocytose at a somewhat lower rate (1% per minute), whereas some amoebae ingest their plasma membrane even more rapidly.
It seems to me that pinocytosis can't take place when surrounded by a cell wall..
FZ+
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Feb20-04, 02:46 PM
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A cell wall is a rigid structure, so I wonder how organisms with such a structure are able to take up nutrients from their environment?
Not sure how helpful this is, but...

http://botit.botany.wisc.edu/courses...dex_to_EC.html

The Cell Wall: In tissues, the primary plant cell wall is perforated with cytoplasmic tunnels that connect the protoplasts of adjascent cells. These channels are barely resolvable with the light microscope. In lab students view tissue from the endosperm of Diospyros (Persimmon). In this tissue, nutrients are stored in the form of hemicellulose in the primary walls. Because these walls are so thick the plasmodesmata are extremely long and this renders them visible to the light microscope. The boundary between adjacent cells (the middle lamella) is also clearly visible in the tissue.
Plus image:
http://botit.botany.wisc.edu/courses...Diospyros.html
eagleone
#7
Feb21-04, 08:15 AM
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Those walls are totally transparent with big enough holes, so they aren’t obstacle for that kind of transport, and as mentioned - cells extend their plasmodesms throo wall…
garytse86
#8
Feb28-04, 09:29 AM
P: 310
transport proteins?
dr_syed_ameen2000
#9
Mar12-04, 06:42 PM
P: 14
march.12.2004
The cell walls are comprised of membranes,as you said,but what membranes are comprised of are the molecules.The molecules have reactive centers due to their electronegativities of their attached neighbours or wandering fluids which come closer to them.Lysosomes are the sets of enzymes packed inside bags made out of membranes,when the membranes rupture they are released and some of those enzymes are hyrdolysing system.One theory of lysogeny describes the phenomenon of death due to release of lysosomal enzymes which kill the cells.Also you have to realize a phenomenon called "the ACTIVE TRANSPORTATION OF IONS",this involves irreversible and nonlinear thermodynamics,like k and ca ions compete to get inside,though the ca is bigger,it accomplishes its task by active transportation,involving reactions thru molecules of the membranes.There are many things involved which makes the biological processes very complicated.Physics that way is easy to understand than biology,for me.
Monique
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Mar13-04, 04:11 AM
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Yes, molecular transport mechanisms are active in membranes. But the cell wall is an entirely different structure.

Look for instance at the following picture of a Gram+ bacterium(meaning it has an outer rigid cell wall):


The cell membrane are the spheres (hydrophilic) with the tailes (hydrophobic), you can see how a molecule spans both membranes or how a molecule is attached to the plasma membrane.

Above it you can see the cell wall, made up of a crosslinked polymer of peptidoglycan. I don't see how molecules would be transported through that, besides through diffusion (which would exclude large molecules).

Actually, I just read that G+ cell walls are negative in charge and hydrophilic, and the G- cell wall is very hydrophilic and acts like a barrier to hydrophobic molecules..
dr_syed_ameen2000
#11
Mar15-04, 06:39 PM
P: 14
march.15.2004
Monique:
The hydrophilicity and hydrophbicity are realtive terms since the membranes are made of molecules,where,even if we consider them as rigid and nonreactive to the aqueous solutions,one can see like in crystal structures the regions of conductivity.So the membranes must have some regions where certain differences in conductivities must exist.As we have some information in regards to the DNA molecules also which have been pointed out as showing some regions of Superconductivity.Although the chemist have some questions but it is possible even if considering the hydro philic and hydrophobic regions of membranes where the Conducting behaviors must be realised.
In case of mentioning the Thermodynamic aspects,as I suggested that the LINEAR AND NON LINEAR THERMODYNAMICS and REVERSIBILITY AND IRREVERSIBILITY of reactions on membrane SITES might participate also where it must be included to see the ACTIVE TRANSPORTATION of elements of even molecules thru.Long time ago I was doing some research in New York,helping one medical professor on research.On lever cell membranes.There was some research on active transportation of cat ions,like
Ca+ and K+ and Sr++ etc. across cell membrane,using the Isotopes.It was surprised to see the bigger ions like Ca+ etc, specifically got inside diffused compared to K+ which was smaller,or so.Why?This investigation suggested that the membrane of cell specifically selectively picks up bigger one to get inside than smaller one in that case.This later I explained was due to ACTIVE TRANSPORTATION where some protein or enzyme or macromolecule which constitute the membrane structure must play a role to perform this reaction.That realm od Irreversible and Nonlinear thermodynamics.What gets in specifically can not get out.This means diffusion is thermodynamically controlled or Kinetically controlled reaction for these species.
So you must figure out the nature of the processes whether thermodynamically or kinetically control.Hydrophilicity and hydrophobicity ,in my view are related to these control mechnisms.
Now I am not in Bichemistry and presently solving the nature and origin of PHOTON dielemma which Einstein and Feynman could not understand.My imagination had come to show the true nature where they failed to percieve.see: http://www.geocities.com/dr_syed_ame...DISCOVERY.HTML


Dr.Syed Ameen(Ph.D.)
Monique
#12
Mar15-04, 11:56 PM
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I am very aware of active transport of molecules across membranes. In order to understand my question you should study the molecular difference between a MEMBRANE and a CELL WALL. They are very different structures, the point is that I don't see active transport happening across a cell wall.
dr_syed_ameen2000
#13
Mar18-04, 07:43 PM
P: 14
march.18.2004

Monique:
You are missing the point I made.Membranes are made up of molecules.They are not just walls of nothing.Even the brick walls are made up of molecules.The membranes have lipoprotein type of structures.I would like you to think of structures and mechanism in organic chemistry.All biochemistries and biophysics are dependent on the nature of Chemical bonds.It also would show you some Proteins which act like electronic swithces,and electronic Gates,opening and closing in response to the presence of specific molecules in the proximity.The membranes (monolayers or multilayers comprise of molecules of certain characterstics ,as you mentioned before ,phobicities and philicities to solvents like water oetc.The active transportation across membranes is a know phenomenon and well demonstrated in scientific literatures.Lars Onsager's reciprocal relationship,also plays a role in membrane chemistry and physics.My former mentor Manfred Eigen has some one of his group indulge at membrane research at Max Planck Institute fur biophysikalishce chemie at gottingen,Germany.So I know a lot about thing in membrane physiology and metabolic chemical reactions.Look again what aspects of thermodynamics could be involved,you will find a surprise.
Dr.Syed ameen(Ph.D.)
Monique
#14
Mar19-04, 12:01 AM
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Originally posted by dr_syed_ameen2000
march.18.2004

The active transportation across membranes is a know phenomenon and well demonstrated in scientific literatures.
Sure Syed, I know, I can calculate exactly how much energy it would take to transport a neutral molecule such as glucose against a certain concentration gradient across membranes. The thing is: I am NOT talking about membranes, I am talking about cell walls!

Look at the following cartoon I posted previously, both structures are depicted:
http://www.bact.wisc.edu/MicrotextBo...es/GramPos.jpg
Mike H
#15
Mar20-04, 11:14 AM
P: 484
Monique,

You may be interested in finding this paper and seeing if the references help to start you on your way:

Cellular impermeability and uptake of biocides and antibiotics in Gram positive bacteria and mycobacteria.

Based on this, if antibiotics and biocides - which while not small are of some not insignificant size - are able to pass through a Gram positive cell wall, most nutrients of use (amino acids, small carbohydrates, etc.) can probably make it through to varying degrees.

I have another reference source I can check without it being too much of a hassle, I'll try to see if I can sneak a look at it in the next few days.


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