Regulating the Cell Cycle: Activities and Concepts

Participation Regulating the Cell Cycle Activate Prior Knowledge – Growth Hormones Assess the following scenario: Two athletes are brought before an investigating committee because both tested positive for growth hormones. One athlete, a record holder, denies ever knowingly taking the growth hormone. The other recently had knee surgery and was taking the drugs prescribed by the doctor. Write a short response in which you speculate on how the growth hormones were being used by the athletes. As a class, we will discuss the question: What does the cell cycle have to do with this story? Build Vocabulary – Academic Words The verb regulate means “to control or direct.” Therefore, a substance that regulates the cell cycle controls when the cell grows and divides. Build Study Skills – Cell Cycle Regulation Analogy Develop an analogy to grasp the importance of cell cycle regulation. Many everyday tasks require a regulated system to be completed successfully. For example, to make a peanut better and jelly sandwich, you need to lay out the bread before you put jelly on the knife. You also need to control how much peanut better and jelly are used to make the sandwich. In small groups of 2, think of a daily task that requires a sequence of regulated steps. One student will present the group’s analogy to the class. The presentation should include the steps involved and what could go wrong if regulation goes awry. Think about the phases of the cell cycle: Interphase, prophase, metaphase, anaphase, telophase, and cytokinesis. What could go wrong if the cycle is not carefully regulated? Differentiated Instruction – Activity Analogy Use an activity analogy, such as riding a bike, and write down the steps that need to occur for the activity to be completed. Discuss with a partner about how the activity is regulated. Zooming In – Cell Growth and Healing When a person breaks a bone, cells at the edges of the injury are stimulated to divide rapidly. The new cells that form begin to heal the break. As the bone heals, the cells stop dividing and growing. Compare the way a wound in the skin heals and the way a broken bone heals. Mystery Clue – Pet Shop Accident How might regulatory proteins be involved in wound healing in the salamander? Which type of regulators – internal, external, or both – are likely to be involved in the salamander’s wound healing. How do the regulators ensure that some types of tissue do not grow faster than others? In Your Notebook – Cause and Effect Diagram Use a cause-and-effect diagram to describe how internal and external regulators work together to control the cell cycle. Biology In-Depth – Healing of a Broken Bone Several stages are involved in the healing of a broken bone. The stages reveal the complex nature of bone tissue, of which you are probably not aware. When a bone breaks, blood vessels are torn apart and a massive blood clot forms. Many bone cells die because they are cut off from oxygen and nutrients. Within a few days, a soft callus forms. New capillaries grow into the area and bring oxygen and nutrients to the repair site. Immune system cells begin to remove dead cells and other debris. Bone cells from surrounding areas move into the damaged area. These cells produce collagen fibers and bony substances that form a bridge between the ends of the broken bone. Soon, the soft callus hardens and forms a bone callus (shown in Figure 10-14). Even when all of the bone structures are re-formed, the healing is not complete. As the person resumes a normal activity level, the new bone tissue will react to mechanical stressors and alter its configuration. Lead a Discussion – Apoptosis Make sure that you understand that apoptosis is a normal cell process and is beneficial to many organisms. In fact, apoptosis is a necessary process for multicellular organisms. Apoptosis allows organisms to more fully control which cells continue to grow and divide and which do not. If a cell is old or damaged, apoptosis allows for this cell to be destroyed rather than continuing to grow, divide, and use the resources that other healthy cells need to survive. Differentiated Instruction – Apoptosis You may think that apoptosis – programmed cell death – is always a sign of a disease. Apoptosis is an important event for the health of a multicellular organism. For example, old cells, such as skin cells, must be removed so that new cells have space to grow. If old skin cells did not die and shed, what would happen to a person’s skin? Discuss why apoptosis is beneficial to multicellular organisms. Analyzing Data – The Rise and Fall of Cyclins Scientists measured cyclin levels in clam egg cells as the cells went through their first mitotic divisions after fertilization. The data are shown in the graph. Cyclins are continually produced and destroyed within cells. Cyclin production signals cells to enter mitosis, while cyclin destruction signals cells to stop dividing and enter interphase. Analyze and Conclude: 1. Interpret Graphs How long does cyclin production last during a typical cell cycle in fertilized clam eggs? 2. Infer During which part of the cell cycle does cyclin production begin? How quickly is cyclin destroyed? 3. Predict Suppose that the regulators that control cyclin production are no longer produced. What are two possible outcomes? Assess and Remediate – Evaluate Understanding A student will be cold called to explain what regulates the cell cycle. Be prepared, scholars!