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.
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:
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:
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!