Transcript cells
Happy Wednesday Bellwork: Quickwrite: In 26 words, describe how you think the body grows and develops on a cellular level? Objective: What are the steps of the cell cycle? In most cases, living things grow by producing more cells. The two main reasons that cells divide rather than continue to grow indefinitely are: 1) the larger a cell becomes, the more demands it places on its DNA. 2) the cell has more trouble moving enough nutrients and wastes across the cell membrane. The information that controls a cell’s function is stored in a molecule known as DNA. If a cell continued to grow larger without dividing, its DNA wouldn’t be able to serve the increasing needs of the growing cell. Food, oxygen, and water enter a cell through its cell membrane, and waste products leave in the same way. The rate at which the exchange of materials takes place across the cell membrane depends on the surface area of the cell. The rate at which food and oxygen are used up and waste products are produced depends on the cell’s volume. As a cell increases in size, the volume increases much more quickly than the surface area. This is a problem because if the cell gets too large, more difficult to get sufficient amounts of oxygen and nutrients in and waste products out. Before it becomes too large, a growing cell divides forming two “daughter” cells. This process is called cell division. Cell division solves the problem of information storage because each daughter cell gets one complete set of genetic information. Cell division solves the problem of surfacearea-to-volume-ratio by increasing surface area and decreasing volume. The cell cycle is the series of events that cells go through as they grow and divide. During the cell cycle, a cell grows, prepares for division, and divides to form two daughter cells. G1 DRAW THIS!!! S G2 Interphase is divided into the G1, S, and G2 stages. During the G1 phase, cells increase in size and make new proteins and organelles. During the S phase, chromosomes (DNA) are replicated (copied). During the G2 phase, many of the organelles and molecules required for cell division are Assembled. When the events of the G2 phase are completed, the cell is ready to enter mitosis and begin the process of cell division. All cells do not move through the cell cycle at the same rate. Muscle cells and nerve cells do not divide once they have developed. Skin, digestive tract, and bone marrow cells divide rapidly throughout life. Cancer is a disorder in which some of the body’s own cells lose the ability to control growth. Cancer cells do not respond to the signals that regulate the growth of most cells. Cancer cells divide uncontrollably and form masses of cells called tumors. Tumors are harmful because they damage surrounding tissues. Cancer cells may break loose from tumors and spread (metastasis) throughout the body. Cancer may be caused by tobacco, radiation, or viral infection. All cancers have one thing in common: The control over the cell cycle has broken down. A large number of cancer cells have a defect in the p53 gene. The p53 gene normally halts the cell cycle until all chromosomes have been replicated.