Learning Goals

Learning Goal

We will investigate the structures and functions of cells, and the environmental factors that influence cellular activity using light microscopes (physical and virtual) and slide staining procedures.

Success Criteria for Full Lesson

  • We will develop an understanding of ‘size’ of organelles in relation to cell size.
  • We will review the differences between plant and animals cells.

Today’s Work:

Please read and make notes on the following.  There are also 3 questions to submit with your notes.

History of Cell Theory

It was once believed that spontaneous generation could turn non-living things into simple living things. These observations were not made through the scientific method but by untested observation.

For example, it was once believed that if you left mouldy grain out, it would spontaneously turn into mice. Therefore it was concluded that mouldy grain turned into mice. Today we know that the thatched roofs used in the past would leak and the water would spoil the grain and attract the mice.

An example of spontaneous generation that did get tested was the belief that rotting meat would spontaneously turn into flies. In 1668, Francesco Redi did an experiment with flies and wide-mouth jars containing meat. He used two jars of meat; one was covered with a fine mesh and the other was left open. Flies could only get into the open jar and after a brief period of time, maggots and eventually flies were found in the open jar. However, flies and maggots were not found in the jar covered by the mesh. He was able to conclude that the rotting meat in the covered jar did not spontaneously generate flies, whereas the open jar that had flies continued to have more flies over time. He was able to conclude that flies come from flies and not from rotting meat. Therefore, living things come from other living things; it was the first step into developing the cell theory.

Around the same time as Redi, Robert Hooke, using his new microscope, observed the structure of plant cell walls and he was the first to use the term ‘cells’.

In 1838, Matthias Schleiden and Theodore Schwann were looking at tissues with their microscopes. They were able to determine that all living things were made up of cells. They eventually developed the first cell theory:

  1. All living things are composed of one or more cells.
  2. Cells are the basic structural and functional units of life.

Modern Cell Theory

It was through the earlier work of Redi, Hooke, Schleiden, and Schwann that Rudolf Virchow was able to complete the cell theory. Since he was a doctor of medicine, he was interested in human disease. Through the use of a microscope he was able to observe cells dividing. He further modified the cell theory to create the modern cell theory that now states:

  1. All living things are composed of one or more cells.
  2. Cells are the basic structural and functional units of life.
  3. All cells come from the division of other cells.

The Cell Cycle

The entire life of the cell is called the cell cycle. Within the human body the cell cycle happens in every cell, except nerve cells after the age of three. In plant cells, the cell cycle occurs in specialized parts called meristem located in the tips of roots and shoots. Below is a diagram of the various stages of the cell cycle.

The Cell Cycle, Mitosis and Meiosis — University of Leicester

The cell cycle can last about 24 hours. There are two major phases in the cell cycle, interphase and mitosis. The period between divisions is known as interphase and takes the majority of time. The second part is cell division or mitosis and lasts about one hour.

  • The first phase of interphase is called Gap 1 or G1. Metabolic changes prepare the cell for division. At a certain point called the restriction point, the cell is committed to division and moves into the S phase.
  • The second phase is called S or synthesis phase. DNA synthesis replicates the genetic material so that there are two identical copy of it. Each chromosome now consists of two sister chromatids.
  • The third phase is called Gap 2 or G2. Metabolic changes assemble the cytoplasmic materials necessary for mitosis and cytokinesis.
  • The last phase of the cell cycle is called M phase for mitosis. This is the creation of a new cell that is identical to first cell.

The cell cycle is responsible for the growth and development of all body cells. It ensures that all human body cells contain 46 chromosomes after division. This process can speed up in response to infection or injury; most of the functions that keep you alive boil down to the cell cycle.

How do cells divide?

The process of cell division is called mitosis, which means the division of nuclear material in the production of new cells. Basically humans start out with one body cell and create more. However, the trick is to create an identical cell to the first. Both cells, the original cell and the new cell, have to be identical with the same blueprints or DNA. Mitosis involves four steps and together they are how the genetic material is divided up. The four phases are:

1. Prophase

2. Metaphase

3. Anaphase

4. Telophase

Cell Division - Mitosis and Meiosis | Ask A Biologist

 

Questions

  1. The ancient people of Egypt once thought that during the yearly flooding of the Nile River, that left behind nutrient rich mud, a large number of frogs appeared that were not there in drier times. They concluded that the muddy soil allows the spontaneous generation of frogs. Explain what you think was happening.
  2. Using the modern cell theory, how are new living things produced?
  3. a. Write the numbers from one to eighteen in your notes. Next write the name of the phase (interphase, prophase, metaphase, anaphase, telophase) for each of the numbered cells in the image below.
    b. Which phase occurs most frequently?

Learning Goals

Learning Goal

We will investigate the structures and functions of cells, and the environmental factors that influence cellular activity using light microscopes (physical and virtual) and slide staining procedures.

Success Criteria of Full Lesson

  • We will understand each of the organelles’ jobs within the cell.
  • We will be able to recognize how the organelle’s job will affect the cell if it is removed.
  • We will be able to identify the organelles by appearance.
  • We will be able to label a plant and animal cell.

Today’s Work

Learning GoalLearning Goals

We will investigate the structures and functions of cells, and the environmental factors that influence cellular activity using light microscopes (physical and virtual) and slide staining procedures.

Success Criteria for Full Lesson

  • We will develop an overview of the historic development of our understanding of carcinogens (cancer causing agents).
  • We will understand the cell cycle and cell division timing.
  • We will develop an understanding of mutations required within the cell that causes cancer development
  • We will reflect about growth in our understanding of cancer. We will determine what we might change in our lives to limit the potential of having cancer.

Today’s Work

Download this activity worksheet it has the instructions and can be filed in as you work through the video clips below.  Keep in mind that you will be asked to reflect on your learnings after you have completed the worksheet (either a video blog or a podcast – voice recording).   Your reflection should be organized and should cover the following items…

  • The most interesting thing I learned about cancer today was…. because… (give at least 2 reasons why it was interesting).
  • Cancer touches all of our lives in some way, how have you or will you try to lessen the chances of cancer impacting your life?
  • **These podcasts or video blogs will be collected and shared with the class.  Put up your thoughts on the Flipgrid.  Class code: learninghood3c

Uncontrollable Growth

Sometimes the cell cycle can get out of control. This occurs when the rate of cell division increases beyond the natural rate of mitosis. This can happen in both plants and animals and can be caused by a variety of mutagenic agents called carcinogens, which are cancer-causing agents. Scientists have identified some of these agents that include smoking, asbestos, viruses, solar radiation, and chemicals. These substances can lead to tumours, which are abnormal cell masses. What makes cancer so dangerous is that its growth is uncontrollable. These cancerous cells use up too many resources in the human body. They interfere with normal cells by consuming nutrients, oxygen, and space. They have a much shorter interphase and do not grow or specialize.

Another problem with cancerous cells in the body is that they may be stationary or mobile. The stationary cancerous cells can be killed by chemotherapy or removed surgically, however, the mobile cancer cells use the human circulatory system to move to different locations around the body and then begin causing harm all over again. Since they are not specialized they can grow almost everywhere in the body.

 

** If you need to complete this task online (if you did not finish the Tablet activity in class) you can access the videos…

Post your thoughts in the Flipgrid below.  Use your @granderie.ca email address to gain access to post!