Tissue Engineering Problem - Find minimum starting cell population

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Discussion Overview

The discussion revolves around calculating the minimum starting cell population required to create a tissue-engineered blood vessel using smooth muscle cells, considering their exponential growth characteristics. Participants explore the mathematical modeling of cell growth over a specified time frame.

Discussion Character

  • Homework-related
  • Mathematical reasoning

Main Points Raised

  • One participant states the need for at least 5 trillion cells to create the blood vessel within four weeks and mentions the doubling time of smooth muscle cells as 15 hours.
  • Another participant highlights the concept of exponential growth and suggests that the math for exponential decay is similar, indicating that understanding these concepts is crucial for solving the problem.
  • Concerns are raised about the ambiguity of the term "trillion," which can refer to either 1012 or 1018, suggesting the use of scientific notation for clarity.
  • One participant describes a method to calculate the starting population by considering the number of halving times over the four-week period, implying that the starting population can be derived from the target population divided by powers of two based on the doubling time.
  • Participants express uncertainty about their calculations, with one noting an answer of 5.6e11 and questioning its validity, while another confirms the formula involving 1e12 multiplied by (0.5) raised to the power of the number of halving times.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the correct starting population, as there are differing interpretations of the calculations and the meaning of "trillion." The discussion remains unresolved regarding the exact minimum starting cell population needed.

Contextual Notes

There are limitations related to the assumptions made about the doubling time and the interpretation of "trillion," which could affect the calculations. The discussion also reflects uncertainty in the mathematical steps taken by participants.

bmed90
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Homework Statement




You want to create a tissue engineered blood vessel using smooth muscle cells. Your plan is to isolate smooth muscle cells from discarded human tissue obtained from heart surgery and grow them for a long time to create cells own ECM. Smooth muscle cells have enormous groth potential in culture and assume they have a doubling time of 15 hours. If you need at least 5 trillion cells to make the blood vessel in four weeks what minimum starting cell population would you need?

Homework Equations





The Attempt at a Solution

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I've tried several attempts and I don't think they are even worth posting. Cant seem to get reasonable answers.

 
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This is about exponential growth. It will be probably easier to find information about exponential decay, but the math is the same, just works in a different direction.
 
Everyone should understand exponentials but this is a biologist in a hurry. :biggrin:

According to Wikipedia a trillion can mean either 1012 or 1018 which is not a negligible difference. So use scientific notation please.

The cell population doubles in 15 hours. So if it's a trillion (whatever that is) now, it was half a trillion 15 hours ago. It halves every 15h you go back in time. So how many halving times, how many 15 h are there in 4 weeks? So the number of cells you needed to start with is (a trillion) X (1/2)^ raised to the power of that number of halving times. In other words you multiply by a half for every 15 h.

What was unreasonable about the answers you got? Was it less than one? Doesn't mean the maths was wrong. What does it mean?
 
epenguin said:
Everyone should understand exponentials but this is a biologist in a hurry. :biggrin:

According to Wikipedia a trillion can mean either 1012 or 1018 which is not a negligible difference. So use scientific notation please.

The cell population doubles in 15 hours. So if it's a trillion (whatever that is) now, it was half a trillion 15 hours ago. It halves every 15h you go back in time. So how many halving times, how many 15 h are there in 4 weeks? So the number of cells you needed to start with is (a trillion) X (1/2)^ raised to the power of that number of halving times. In other words you multiply by a half for every 15 h.

What was unreasonable about the answers you got? Was it less than one? Doesn't mean the maths was wrong. What does it mean?

Well honestly I can tell you right now that whatever I got was wrong. I got like 5.6e11... So your saying the answer is 1e12(.5)^44
 
bmed90 said:
So your saying the answer is 1e12(.5)^44

44.8 to be precise.
 
bmed90 said:
Well honestly I can tell you right now that whatever I got was wrong. I got like 5.6e11... So your saying the answer is 1e12(.5)^44

Yes. Which is...?
 
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