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Biology/Saprotrophic organisms

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QUESTION: Hello, I would like to ask you a question regarding something from the biology exam program. It sounds something like this:
"Explain the main qualities of saprotrophic organisms' cellular structure."
So far, the only thing I could find was their unicellularity, but I can't quite understand how exactly - bigger area to volume ratio or something? Could you explain it and give examples for what specific cellular qualities aid fungi and bacteria that feed this way? (at least one for both if you may).

Thank you in advance,
Mindaugas

ANSWER: Hi Mindaugas.
This is the first question I have ever received from Lithuania.
 The organisms you are considering here include the bacteria as well as the Fungi although the cells of the bacteria are different having no organized nucleus. However the methods of gaining energy through the cell membranes are the same. Both types take in digested nutrients by endocytosis. Bacteria also take in nutrients through phagocytosis.
You have mentioned the surface area to volume ratio. Simple math can explain this. There is a math principle called the Scale effect which states that as the size of a cell increases the SA- Vol ratio decreases.  Think about a cube with a side of 1 mm:
 The surface area would be 1 x 1 x 6 (six side) or 6 square mm
 The volume would be 1 x 1 x 1          or 1  cubic mm   Ratio 6 to 1
    Now we double the size to 2 mm on a side
 The surface area would be 2 x 2 x 6          or 24  square mm
 The volume would be 2 x 2 x 2          or  3 cubic mm   Ratio is now 3 to 1

The math is the same no matter what the cell shape is. What does this all mean to the cell?
The larger the cell the greater the metabolic needs. Nutrients must pass through the cell surface and wastes must pass out. Cells solve the problem by dividing. this is why cells are small.
 I realize that I may have used terminology that you are not acquainted with.
 If I have answered your question let me know.



---------- FOLLOW-UP ----------

QUESTION: Thank you for your quick reply, but it was not what I was seeking.
I suppose I just did not formulate it correctly.
What I wanted to know, was what cellular characteristics are unique to saprotrophic organisms. I know the general structure of bacteria well enough and there is an abundance of information on that, but how do saprotrophic bacteria differ from the rest? More permeable membranes? More carrier proteins for active transportation? I just can't find any info to validate such assumptions.
As I mentioned, the only hint I could find was unicellularity and I assumed that it had to do with the SA-Vol ratio. Am I correct on that assumption? But then, what about fungi? Not all saprotrophic fungi are unicellular. What unique characteristics do they have then, compared to a regular cell? I am just hard pressed to find any and I was hoping you would have an idea.

Thank you once again,
Mindaugas

Answer
Some bacteria cells absorb nutrients that are already broken down. Saprophytic bacteria cannot do this and they secrete exogenous enzymes that break down organic material and then absorb it. his is how they differ from the rest. Our intestinal bacteria do this. They do not have more membranes or carrier proteins. They are the good guys who recycle organic material
 The Fungi are eukaryotes with a nucleus and cell organelles. Some secrete digestive enzymes and some can take it larger molecules and digest them inside the cell.
 I hope all my math was for nothing. The SA - Vol ratio is important for all cells whether organism is single or multicellular. It explains why cells are small
I am not sure what you mean by the term "regular" cell. There are two types of living cells: Prokaryotes and eukaryotes.

 Maybe I got it right this time

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Walter Hintz

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Science teacher for over 50 years. MSc. in biology. I can answer questions in general biology, zoology, botany, anatomy and physiology and biochemistry.

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I have a MSc in biology and have been a science teacher for over 50 years. At present I am a faculty member at a college and a science consultant at seven catholic schools.

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