Cell Growth - Unit 3 Lesson 13
Question - how many cells is your body made up of?
And that’s not even counting the trillions of bacteria cells that live with you
Next question - how many cells did you start off as?
So how do you go from a single cell to trillions of cells? Well, your cells divide and, by doing so, they multiply! Cells divide and multiply? Is this some sort of math riddle?
What I mean is, cells grow larger until a certain point where they can’t grow any larger, then they divide in half. So one cell becomes two. Then those two cells grow until they need to divide and then become four cells. Then those four cells become eight cells. The eight cells become sixteen cells. The sixteen cells become thirty-two cells. After 20 such rounds of division, a single cell has become over 1 million cells! (220 = 1,048,576)
So by repeatedly dividing in half, they quickly multiply into huge numbers.
Let’s look at a specific example. The single cell that we all started off as is called a zygote. That first cell takes about 24 hours to replicate (divide). The resulting two cells take another 24 hours to divide. So after two days, the zygote has turned into a 4 cell embryo. After 10 days it will be 1024 cells. After 30 days, the embryo (now called a fetus) will be over 1 billion cells. To be fair, as the embryo is developing, cells start to specialize and some of these specialized cells do not replicate as fast as others. So, in general, cell replication starts to slow down to once every few days as the fetus grows larger. But, by the time the baby is born, it will be made up of over a trillion cells!
Here is the question to consider for the day.
Why do cells need to divide? Why can’t they just keep growing bigger and bigger?
This question should remind you of the Unit 3 portfolio. You may actually remember the answer to this question because of that lab. But, if not, this video will help to remind you. This video is from someone named Mr. Furlong. I don’t know Mr. Furlong but his video is good.