Since we know that our entire body is made up of cells, it is important to learn both where these cells came from and how they continue to grow to perform the specialized functions in our bodies. Recall the cell theory, which has three main points:
all living things are made up of cells;
a cell is the basic unit of structure for living organisms;
all cells come from pre-existing cells.
Throughout this activity, we will be going deeper into the third point, i.e., all cells come from pre-existing cells. While going through this activity, think about the following questions:
How do we know that cells come from pre-existing cells? How is this process observed? Does it happen the same way all the time?
The Cell Cycle
All animal cells undergo a process by which they duplicate to create new cells. This process is what we refer to as the cell cycle.
During the cell cycle, the cell grows, performs its specialized functions and then creates an exact copy of itself. This is a very important process, because this is how we grow and how our tissues get repaired.
The series of images below shows a delicious representation of the cell cycle using doughnuts and sprinkles.
Cells in your body are constantly dividing and creating new cells.
Recall the video you watched during the Minds On section in Activity 5: The Small Stuff about how long it takes for the cells in your body to be replaced. There you learned that there are two main reasons your cells need to divide: growth and repair.
From the moment you are born, you are growing and your cells are dividing rapidly to make you taller and stronger. This process continues throughout your teenage years. You might even be aware at this very moment that you are still growing, perhaps because your jeans are too short or your shoes are too tight!
Repair
When your body is injured, your cells divide to repair the injury. For example, if you break a finger, your fingers need to be immobilized(definition:kept still) so that the specialized cells in your bones can divide to heal the break in your bone. Similarly, if you get a cut on your skin, a scab forms to allow the division of your specialized skin cells for repair of the damaged area.
Remember "you are what you eat" and the importance of consuming healthy foods? There you learned that nutritious meals and snacks fuel the cell division that helps your tissues grow and heal.
The Cell Cycle and Mitosis
The cell cycle consists of three stages:
1. Interphase, which is where cells grow, perform their functions and replicate DNA;(definition:stands for deoxyribonucleic acid, which is the carrier for your genetic information)
2. Mitosis, which is the process of cell division;
3. Cytokinesis, which is the final splitting into two genetically identical cells.
Since Mitosis is a complex process, it is broken down into four phases: Prophase, Metaphase, Anaphase and Telophase.
The image below demonstrates how the majority of the cells in our bodies spend their "lifetime."
Watch this video of kidney cells undergoing the cell cycle. You will see that the various stages happen very quickly.
You probably noticed that the majority of the cells dividing in the video looked very similar to one another.
Were you able to identify the cells when they were in Interphase, Mitosis and Cytokinesis?
If you watch closely again, you should notice that the cells surrounding the dividing cell are generally in Interphase.
Tips for Using Cornell Notes
Cornell Notes can be a helpful tool for organizing and summarizing information. They can be especially useful when watching videos. If you are new to them, use this template and watch this video to get started.
Now watch this video on Mitosis and the cell cycle.
The video is divided into five segments. Use Cornell Notes to summarize each one.
Part 1: Introduction
Here is an example of what your Mitosis notes in Cornell Note style might look like.
Part 4: Prophase, Metaphase, Anaphase and Telophase
Part 5: Cytokinesis
Earlier in this activity you analyzed and organized images into the stages of the cell cycle. Now you will add the functions to each stage. Complete the interactive and save the Cell Cycle order in your Portfolio.
Now that you are familiar with describing Mitosis and the cell cycle, take a look at some whitefish blastula cells under the compound microscope. These animal cells clearly show Mitosis.
When you looked at the whitefish cells under the microscope, which stage of the cell cycle represented the most cells in view? (Hint: count the cells in each stage.)
Which stages of the cell cycle were represented (Interphase, Prophase, Metaphase, Anaphase or Telophase)? How do you know?
Do you find it amazing that every person and living thing that has ever existed initially began as a small cluster of rapidly dividing cells?
CONSOLIDATION
Cancerous Cells
Through the course of your life, you will probably know someone (whether a friend, family member or co-worker) who has been affected somehow by cancer. But did you know that cancer actually occurs when Mitosis malfunctions in your cells?
Cancerous cells divide at an unregulated speed. It is similar to having a car that can be driven quite fast but has no brakes. These cells divide very quickly and can form tumours,(definition:abnormal cell growth that serves no purpose) which can also break apart, enter your blood and unfortunately be transported to other areas of your body.
Watch this video simulation showing a comparison of normal cell division with cancerous cell division.
What similarities and differences do you observe? Use a Cornell Note to record these.
Now watch the same video with normal and cancerous cell division shown side-by-side. Add to your Cornell Note on this.
Tips for Thinking Critically
The internet is packed with videos that look really flashy, but how can you be sure their information comes from a good source? Watch this video all the way to the end to be reminded of how to think critically about other videos you might find on the internet. (Hint: this is a fake one!)
Remember to look at the source of the video and what information it provides before you decide to belive it!
Tips for Using Cornell Notes
What Do You Think?
Learning Goals and Success Criteria
Learning Skills and Work Habits