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Why we should STOP teaching the nucleus is the control center of the cell

11/15/2017

6 Comments

 
Why we should STOP teaching the nucleus is the control center of the cell
Why you should stop teaching the nucleus is the control center of the cell
Why the nucleus isn't King of the castle
Ever since middle school when students learn about cells, they are taught that nucleus is the control center of the cell. They hear that the nucleus is "the brain" and in charge of all cell functions. When teachers do the cell-as-a-factory analogy, the nucleus ends up being the boss. This is not technically true... while the nucleus houses all the information the cell needs to complete different tasks, it isn't in charge of when that information is used. We need to make sure students understand why cells do the things they do, and it all comes down to cell signaling.

Cell Signaling
Cells complete cellular processes when the cell membrane gets a signal from the outside environment. Once the signal is received, then the cell will respond by using the genetic information in the nucleus to carry out the task. That task will generally keep going until the signal is terminated. Here are a few examples:
  • When red blood cell levels are low, the kidneys release a hormone that signals and stimulates the bone marrow to produce more blood cells. 
  • When your stomach is empty, it absorbs a hormone called Ghrelin, which signals brain cells that you are hungry. When the stomach stretches after eating, hormone absorption stops.
  • When something goes wrong in a cell or it grows too old, a stimulus will activate a protein called caspase, which causes cell death (apoptosis).
You see, the only way a protein or gene knows what to do, is because an environmental signal sent a message to the cell. The gene did not self-activate.

How to get students thinking:
This can be a tricky concept to introduce to students. High school students don't usually understand how the cell operates as a whole and communicates with the outside environment. A great way to introduce the topic is by posing them these questions: "Are identical twins truly identical? Is it possible for one twin to get cancer while the other does not get cancer?" Most students will say yes, this is possible. But if they have the same genes, how can this be? Our cells are not pre-programed to behave based on our DNA. Genes are only regulated based on signals from the environment. Many students also get confused when we talk about "the environment," because they are so used to hearing this term used in ecology. Make sure students understand that the cell has its own environment within the body.

The moral of the story:
  • Teach students that the nucleus is an organelle that contains DNA inside.
  • The nucleus is not in charge of cell activities. (If this were the case, every disorder you are predisposed to have would be manifest. We know this is not the case).
  • Cells do things because they respond to signals from their environment, many of which come from the cell membrane.

The Cell Membrane close reading article from Science Lessons That Rock
Do you want your students to read an article on this topic? Check out this close reading article I wrote available in my TpT store. It is a 3 page article with reading comprehension questions at the end for students to answer. The article covers an overview of: proteins and the central dogma, the lipid bilayer, and epigenetics. It does not cover the details of the types of cell signaling. I believe it is written at a level where most high school students can fully understand the concept of cell signaling and the cell membrane.

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Would you like lab ideas for teaching about the cell membrane? Check out this blog post!

6 Comments
Tanja link
11/22/2017 06:44:50 am

I teach my learners that the nucleus is the library that stores reference books like encyclopedia that cannot be removed. The books contain recipes/instructions for building a variety of products needed in the cell.

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Becca
11/22/2017 06:56:57 am

I love that analogy! Especially that they are books that can't be checked out!

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Mark Mclean link
11/22/2017 07:47:01 am

Great analogy!

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JenT
10/19/2018 11:20:27 pm

I do that too. In fact I say that the DNA is like a huge recipe book that is kept in the living room, but it is so HUGE that it can't be carried to the kitchen, so "photocopies" are made of the specific genes that are needed at any given moment - those are the mRNAs. Because those are small they can leave the living room (go through the nuclear pores) out to the kitchen, where they can be read by the ribosomes. I find lots of kids find this analogy very understandable.

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Aulelia
9/16/2018 08:57:10 pm

How would you teach this without confusing ELL students? I teach sheltered ESOL biology to students who are just transitioning from conversational English to Academic English. Understanding just the organelle names is difficult and while I know not everything is technically correct, it seems to be the simplest way to create a bridge to understanding that DNA is the code behind everything, like an instruction manual.

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Becca
9/22/2018 05:25:36 pm

Analogies are a great way to teach organelles. Building upon your instruction manual analogy, the DNA are the instructions, and the nucleus is the book which stores all the instructions. I've also seen the analogy of recipes inside a cook book, and each cook book is a chromosome.

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    I've been teaching science for 12 years at both the middle and high school levels.

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